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Consoles => Magnificent Magnavox => Topic started by: electra225 on June 22, 2018, 10:07:45 PM

Title: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 22, 2018, 10:07:45 PM
1=Run 1
M=Stereo Theater
R=Total Remote Control
418=model 18 in the 400 series
M (suffix)=27" picture tube/CRT

What I know so far.  It has a 93-02-10 amplifier, 57-XX-XX tuner chassis, possibly a 57-16-XX, pending being able to see the number better, 71-00-00 MPX chassis, C36-20-11 TV chassis and an unknown model solid state remote control amplifier chassis.  Two 12" side-firing woofers and two front-firing 4X10 horns.  There are two tubes in the TV tuner, 9 tubes in the radio tuner, three tubes in the MPX adapter, 17 tubes in the TV chassis plus the CRT, and 7 tubes in the audio amplifier.  39 tubes if I have counted right.  It has a replacement "jug" (picture tube) and has at least one GE tube in the TV chassis and one of the 6EU7's in the amp is a Radio Shack tube.  The shield for the IF strip in the radio tuner is missing, so there has been work done on this thing sometime during the last 55 years or so.  This particular model is listed in the 1962 catalog.  The code on the MPX chassis is 424253.  Since there were not 53 weeks in 1962, could this code be for the 25th week of 1963?  This presents the first mystery.  My understanding is that there were no tube Stereo Theaters built in 1963, according to the 1963 catalog.  I need to figure out the code on the MPX adapter.  I have codes for the speakers, but those make no sense to me.  Perhaps someone else can help with that.  I'll post those later.  I haven't gotten codes off tubes yet.

This instrument is alleged to have a "nasty" hum in the output.  If it still hums, that shows the power transformer is good.  That is my first area of exploration. 

This is all preliminary.  This will be a fascinating journey.   :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on June 23, 2018, 06:24:55 AM
The first step taken for "Rest of the Story".  I can't wait for Greg to start on his new baby so we can all learn what makes a Magnavox Stereo Theater tick!

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Alfista on June 23, 2018, 08:40:04 AM
So is this in your possession, Greg? Has your quest finally come to an end???

I feel like we should collectively open a bottle of champagne!

-Tim
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: danrclem on June 23, 2018, 09:11:42 AM
On the speakers there should be a number starting with 232 which is the Magnavox EIA speaker code.  The following number would be the last number of the year it was made in and the following two digits would be the week it was made in.

http://www.recycledsound.net/8_Speaker_EIA_codes.pdf
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 23, 2018, 01:12:21 PM
Tim, it is not actually in MY possession just yet.  Bill is babysitting.  The quest is officially over for a Stereo Theater.  Don't tell my wife, but the next thing is a little Imperial.  Model 1ST665.   :)

Danny, thanks for that information.   The numbers I have for the woofers are 581201 and for the horns 580059.  These might be part numbers.  I need to secure Sams documentation for this thing to help with this.  I'll print those speaker codes so I can refer to them.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 23, 2018, 02:32:44 PM
The speaker numbers I posted earlier are Magnavox part numbers.

There are some nice features on this instrument that I have not seen typically on Magnavox.  They have put usable antenna connections and external speaker connections mounted to the cabinet, instead of kluged onto the back cover.  We also have the biggest rat's nest of wiring I have ever seen, even on a Magnavox.  This certainly can't be the way is was done from the factory.  The two green wires from the phono cartridge to the tuner are wrapped around the power wires to the TV. 

If you notice in the top picture, the amplifier is powered off the TV chassis.  You can see the plug in the right hand side of the picture, toward the top of the TV chassis.  There is a circuit breaker for the TV and an interlock power cord.  There are so many wires I can't really tell, so it begs the question does the remote control work with the entire instrument or just the TV?  If it turns the TV power on and off, adjusts the volume ( done with controls on the tuner) and changes channels, why would it not also change channels on the radio?  I don't see extra wires going to the changer.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: danrclem on June 23, 2018, 08:14:30 PM
See if you can get Bill to look at the speakers again.  The ones that I have saw have more than one set of numbers.  The number that starts with 232 seems to usually be on the basket somewhere.  On the heavy steel on yours that wraps around the magnet it looks like a 32215 and if it has a number in front of it the wires are covering it. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 23, 2018, 08:41:48 PM
That would make the speakers coded for the 15th week of 1962, which makes sense.  Bill was good enough to get those numbers to quell my over-exuberant curiosity.  He got some extremely good pictures, which have been a big help.  It is hard to take good pictures of numbers with all the dangling wires.   :)

Danny, I don't suppose you would have the EIA codes for tubes you could post, do you?  I have misplaced my chart.....  :-[
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 23, 2018, 09:46:41 PM
I have another speaker code for the 12" speakers.  "137-215".  137 is the code for manufacturer C.T.S.  "215" stands for the 15th week of 1962.  Consistent with the "232' code you cited.  I don't know what "C.T.S." stands for, though.  Why would there be two manufacturers' codes on the same speaker?  The "137-215" is printed under the part number on the magnet of the speaker.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on June 24, 2018, 02:43:39 AM
That photograph of the wiring harnesses between all those chassis somehow reminds me of a mid-70's car engine compartment with the rat's nest of vacuum lines and drive belts between the various added emission control gadgets with AC and cruise control tossed in for extra credit. FM multiplex, remote control, tuner subchassis………….I can't even imagine if that were a color set with convergence board
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 24, 2018, 06:20:29 AM
You are referring to the under hood area of a 1983 Oldsmobile 98 with the 307 "Y" corporate V-8.  The only identifiable components that stuck out from the vacuum hose mess was the top of the air cleaner, the air conditioning compressor and the painted fenders.  The rest of the engine was buried with vacuum hoses.  Changing the valve covers, prone to leak and set the car on fire, was a nearly all-day job for a trained and experienced auto mechanic. 

Fortunately for Magnavox, by the time color TV was introduced to the Stereo Theater line, the stereo components were solid state.  That eliminated the multiple chassis and all the associated wiring.  I have worked with Magnavox enough that the wiring does not concern me anymore.  That particular wad of wiring is not designed to be quite that messy.  Methinks the mess is aftermarket.  Magnavox used heavy paper hangers that get torn up by servicing and deteriorate from old age and let the wring fall into the bottom of the cabinet.  In this case, they did not fall onto the hot tubes in the amplifier.  The wiring is typically found with a sticky substance on it that has attracted dirt.  Each wire has to be cleaned with lacquer thinner and then tied up so it does not look so messy.  My intention is to gut the cabinet and have every part of this instrument in my hands at one point. 

"Gloriously Complicated".  That is the theme of my project.  With advancing age and decreasing eyesight and dexterity in my hands, this project will be a grand adventure.  Most people take these things apart, here I am restoring one. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: walyfd on June 24, 2018, 06:59:21 AM
Congratulations on finally finding a viable candidate.  I must say I will miss the thread in the "Wanted" section.

This looks like it'll be a huge challenge...  looking forward to following your progress on it!
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 24, 2018, 07:52:05 AM
I figured we should move the restoration discussion from the "Wanted" section out of respect for moderators and forum integrity.  Larry could move it or I could.   ;)

Thanks for your interest.  I hope we can have some fun with this and maybe I can learn something along the way.  I've wanted one of these for a long time and the search has gotten discouraging at times.  The guys on the old TV forum thought that finding one was impossible.  They were nearly right. 

I have been asked what the round doo-hickey under the picture tube is.  That is the Magnalux sensor.  Magnalux is a system that adjusts picture brightness to room lighting.  I don't know how it works yet.  We'll try to figure it out during the restoration.  The square thing in the picture tube mask is the sensor for the remote control system.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: danrclem on June 24, 2018, 09:08:00 AM
Here's a link with a lot of EIA codes.

http://triodeel.com/eiacode.htm

Don't put too much (if any) stock in the numbers that I mentioned.  The 137215 is probably what I thought was ?32215.  I couldn't see the first number and the 7 is probably what I thought was a 2.  The numbers in the picture are fuzzy and that's just what I thought they looked like.  Come to think maybe it's my eyes that see fuzzy.   ;D   

CTS stands for Chicago Telephone Supply.  I've seen that code before but don't remember what they were in.

You'll have that Stereo Theatre all figured out way before you pick it up and you'll be able to restore it blindfolded.   ;)


Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on June 24, 2018, 10:30:48 AM
There are so many wires I can't really tell, so it begs the question does the remote control work with the entire instrument or just the TV?  If it turns the TV power on and off, adjusts the volume ( done with controls on the tuner) and changes channels, why would it not also change channels on the radio?  I don't see extra wires going to the changer.

Remember that TV tuners use a series of fixed tuned circuits for each TV channel.  Click click click.  But there are more FM stations and sometimes we need to off-tune a little bit, so tuning for FM or AM is usually continuous.  It was different later with digital devices.  But remote tuning on the radio would have been a lot more difficult back then.

There are exceptions.  I have a ca. 1949 Crosley TV with continuous tuning, and had a huge Dumont once with the same.  And in the 1930s there was a rage for electric tuning (usually mechanical, with a motor drive) and later push-button tuning with buttons selecting tuned circuits.  But think what a rat's nest all that would create....

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 24, 2018, 11:26:21 AM
Danny, I sure appreciate the link to the EIA codes and your confidence in my abilities.  I reckon I'll start making a fool of myself early and beat the rush...... :-[

The Phantom Control in a Concert Grand can control the tuner changing stations, so the technology for controlling the radio tuner exists.  I have never seen a remote control for the particular TV set in the Stereo Theater, so I'm not sure what it is supposed to control.  One would think at least channel selection, on-off and volume at a minimum.  Another piece of the investigation on the Grand Adventure.  Gloriously complicated.   :)

Danny, I have been looking for EIA information like that for eons.  I appreciate your guys' contributions.  I think it would be appropriate to make a little plaque and put it inside the cabinet when we get done with this.  Have the names of everybody who contributed as a memorial of the first Stereo Theater restoration.  Bill will be disappointed if this thread is not larger than the "Wanted" one was.   ;)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: 19and41 on June 24, 2018, 11:53:55 AM
It looks like your restoration thread will be a bestseller!
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 24, 2018, 11:59:09 AM
I'm looking forward to your contribution, Rex.  We have been at this dance before.   :)

I wouldn't have made it thru the Concert Grand restoration without your input.

The codes on the TV chassis are "2-25-1"  Twenty-fifth week of 1962, first shift. 

If the speakers are made by Chicago Telephone Supply, that explains the various designs of speakers you see in Magnavox cabinets.  Wonder why Magnavox did not build their own speakers.  Were they out of the speaker business by 1962?  Heffner built the speakers inone of my other Magnavoxes.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on June 24, 2018, 12:01:52 PM
Is that the Oldsmobile with the diesel v8 option. I seem to remember reading that Oldsmobile wound up buying them back from the customer and that case was the original case leading to the lemon law. or was that the Cadillac with the original radio interference prone electronic fuel system ?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: 19and41 on June 24, 2018, 12:10:20 PM
I doubt if they bought them all back.  I had an '81 Toro with a '91 replacement diesel engine.  It was the most comfortable, reliable car I've owned.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 24, 2018, 12:44:03 PM
They were popular in Phoenix for taxi use.  They would idle all day with the air conditioning on and not overheat.  I made a living for awhile removing them from Chevy and GMC pickups and putting in Olds 455 or Buick 455 engines in their place.  Cadillac 500 engines would work as well, but you had to use the Cadillac transmission.  I had customers with GM diesels who liked theirs as well.  The secret was maintenance.  Once they got a lot of deferred maintenance that was needed, they were done.  We removed them from trucks not because they went bad, but because they did not have enough power for a truck.

I was referring to the 5.0 litre, 307 cid Oldsmobile-built "Y" code V-8.  It was a gasoline engine, rated as I remember at 140 horsepower.  It was no fireball, but was reliable and relatively fuel-efficient.  GM put it in all their rear-drive sedans from 1981 to 1987 or so.  It had a four-barrel Rochester carb with computer controls.  It's Achilles Heel was the valve covers leaking.  They were sealed from the factory with silicone.  They leaked with gay abandon.  The carbon would build up from the oil leak and that could start a fire.  There were millions of vacuum lines and lots of plastic that would combust and the fire would take off.  The diesel was a 5.7 litre, 350 cid V-8 rated at something like 120 horsepower.  The Chevy inline six had more power.  Guys hated that engine in a pickup.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: 19and41 on June 24, 2018, 12:54:59 PM
The Achilles heel on mine and others I knew of, was the diaphragm vacuum pump driven by the distributor drive.  It was a task to find a functional one at a scrapyard as each of mine failed.  It would fail the heating system when it quit.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: amglow on June 24, 2018, 01:36:14 PM
Congratulations Greg!  Your perseverance has paid dividends.
The sensor may be located elsewhere, Greg.  I think the square box in the lower right of the mask is the secondary channel selector display.  It would be a good idea with a remote to know what channel you're on. ;-)  Attached is an image I pulled from a Stereo Theatre ebay listing from September 2013 showing the channel display.  That Stereo Theatre was fully electrically restored and sold for $1,295!!

Quote
The square thing in the picture tube mask is the sensor for the remote control system.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on June 25, 2018, 06:49:37 AM
The square box in the lower RH corner of the screen makes sense with what I noticed looking from the back side.  There is a round tumbler device in that corner that has a light behind it. It rotates on a axle type device and would line up with the square box on the front.  Even though I could not see them, the channel numbers must be on the round tumbler.  Good call Paul and your picture confirms it.

Were on page two already!   ;D

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 25, 2018, 09:01:36 AM
That setup sound gloriously complicated.  Bill, you got me on this one.  The guys on the TV forum, too.  So maybe the round doo-hickey under the picture tube is the sensor for the remote control?  There has to be a sensor for the Magnalux somewhere.  There is a lighted channel indicator on top by the channel knob, too, isn't there?

It seems a real shame that people are dismantling ST's just for the amplifier and canning the rest.  They are works of art.  There are some neat features on it.  Wonder what drives the channel indicator in the CRT mask. 

Thank you all for your input here.  The EIA documentation that Danny posted is essential if you want to document something.  It is eight pages.  There are EIA numbers on stuff I would have had no idea had an EIA number.

Bill, it's gonna take several pages for me to make a fool of myself on this thing.  We will have to talk about cars some, too, you know.   ;)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 25, 2018, 09:47:37 AM
Another "DUH" moment during "The Rest of the Story"... :-[

The remote control system in this Stereo Theater shouldn't be an infrared remote.  Hence, no sensor for the remote.  It probably has a little antenna buried in the cabinet somewhere, like Phantom Control in the CG.  The round doo-hickey under the CRT mask is likely for the Magnalux system. 

My apologies to Bill for my failure to "see" what he was trying to tell me.  Sorry, Bill.   :-[

I will be thrilled if this one gets as good a picture as the one Paul posted does.  After I go thru this one, $1295 would not buy it.   :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: amglow on June 25, 2018, 04:14:28 PM
Greg,
Attached is a 1962 catalog image, advertisement, and two styles of Magnavox Phantom bellows remotes.  The advertisement states the wireless remote performs channel selection, loudness, and ON/OFF.  It is probably a two button bellows (ultrasonic) remote like my 1967 color stereo theatre uses.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 25, 2018, 10:52:54 PM
Thanks, Paul.  So the remote control does not work with the stereo, then.

"Ultrasonic".  Does that use radio frequency like the older Phantom Control?  If no antenna, where is the sensor or whatever sends a signal to the remote control chassis?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on June 26, 2018, 05:43:59 AM
    I've seen some of those space command ultrasonic remotes in my younger days, The television front panel has a small round area with a screen to let the sound to a small mike in the back. maybe 1/2 inch diameter.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: amglow on June 26, 2018, 06:02:25 AM
Greg,
I found some extra info on the Ultrasonic remote from another audio forum:
"The remote is a two frequency "whistle" set to 22,000 and 24,000Hz iirc and there is a small amplifier/switching unit with a mic, inside the cabinet."
"I sold a ton of those in the day.  Those remotes were a pain since they could get "out of tune" over time and needed to be "tweaked". We also found that you could shake certain sets of car keys and cause the remote functions to work."
If that's the case, I bet you would drive your pets crazy too! :-)
One more, Greg.  Here is a link with images of the ultrasonic mic and switching unit, plus good explanations:
http://audiokarma.org/forums/index.php?threads/1962-magnavox-what-the-heck-is-this.376106/#post-4741172

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on June 26, 2018, 06:41:47 AM
No apology necessary Greg, it's a learning experience for all!

I think Ed is correct in that the round sensor under the picture tube is the light sensor.  Not sure where the remote mic/sensor is located. It maybe built into the remote electronics which is sitting next to the MPX thing, which is under the radio/tuner. There is a lot of stuff in this cabinet. ;D  Next time I go to the barn I'll check to see if the channel selector under the hood has numbers as well. 

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 26, 2018, 10:13:59 AM
Thank you so much, Paul.  Interesting.  That is the most complete explanation of the remote control system I have seen.  It even tells how to diagnose the system if the remote transmitter is missing.  That is the most intelligent conversation I have ever seen on AudioKarma.  :)

Perhaps I should develop a better attitude towards AK.   ;)

Bill, I  think I see a little red light above the TV tuner knob in one of those pictures.  What is the little red light for?  Remote on? TV on? None of the above?  According to what Paul posted and the information gleaned therefrom, we are looking for a little microphone doodad, location still unknown. 

Magnavox would hide things in the grille cloth.  There should be a pilot light in the grille cloth (maybe) on the end of the cabinet with the "Magnavox" script on it.  Or it could be in the panel at the bottom of the cabinet with the strip of metal running thru it.  The channel indicator in the corner of the CRT mask is just plain cool.  Very 1960's.   :)

Gloriously complicated!   :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on June 26, 2018, 02:15:10 PM
I'll take a peek at things and report back on my finds.  :)

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 26, 2018, 03:06:47 PM
I like this arrangement.  I have all the fun, you do all the work!   ;)

Have I found the "microphone doodad" that controls the remote?  ("Microphone doodad" will come back to haunt me before this project is completed!  ;))

Notice the device, buried in grille cloth (?!) with the red wire coming off it.  Under the tuner.  Could this be it?

Edit:  I looked again at the pictures on AK that Paul posted.  I'm more sure now than I was, although not positive.  The one on AK has the same single red wire coming out as this one does.

You are going to get attached to the old ST, Bill.  You're gonna miss it when it's gone.  You'll have to come down here to help me fix it so you can see if I'm doing it right!   ;)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: walyfd on June 26, 2018, 04:42:40 PM
Any idea what it all weighs?  The furniture quality was so superior then.  Fill it with tube goodies and brace the floor.  I think I heard my house groan when the Fisher took residence...
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 26, 2018, 04:54:24 PM
Bill can tell you more about its weight than I can.  I'm guesstimating it somewhere close to a Concert Grand, maybe 150 pounds.  The cabinet is 2" longer than the CG.

I have a bench made especially for the big Magnavoxes.  4' X 8', 2 X 6 construction, cross beams set 12" on center.  4X4 legs, braced by 1X4's, 32 inches tall.  It takes four of us old guys to get the big ones on that bench. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on June 26, 2018, 05:05:50 PM
          I think the red wire is the ultrasonic sound sensor. There wouldn't be 2 wires because its probably a high impedance piezoelectric pickup and would have a shielded wire going directly into the metal case so to be totally shielded. The other end probably goes to some kind of shielded phono plug and goes Into the remote chassis.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on June 26, 2018, 05:15:03 PM
  the ad also said the unit had "videomatic."  would that be a similar round light sensor that adjusted the brightness with room lighting?   
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on June 26, 2018, 09:16:31 PM
I'm guessing Greg's ST is 200 plus pounds.  It's full of electronics from one end to the other with no room to spare.

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 26, 2018, 10:55:45 PM
I "thought" I saw an ad that called the room brightness system "Magnalux".  That ad does indeed call it "videomatic."  I believe it is safe to assume that the round red thing in the middle of the picture tube is the sensor for that system, whatever we want to call it.  I see the wires for the traditional Magnavox pilot light, but have not found the light yet.  The wires appear to disappear under the TV chassis, for what that is worth.

You said the casters worked fine, Bill, so that will certainly help.  The big instruments are lots easier to handle with casters.  At 200+ pounds I can lift my end, but I don't want to hold it for very long!   ;)

We'll load it in my little trailer that is lower to the ground than the Tahoe.   ;)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 26, 2018, 11:23:27 PM
Three tidbits of nomenclature for today's adventure into "The Rest of the Story"...

*Chromatic Optical Filter
*Video-matic tuning
*Magnalux

(Magnavox LOVES the words "automatic" and "automatically".  Bear with me....)  ;)

The jury is still out on Chromatic Optical Filter.  Just trust me, it's in there.....

Videomatic or Video-matic tuning:

"Video-matic fully automatic TV"
"Videomatic automatically assures you of the best picture, always, regardless of room light".

Magnalux:

"Magnalux Automatic TV Light Meter"

"Like a self-setting camera, this automatic TV light meter measures the room light and automatically adjusts the brightness and contrast- now you can enjoy the best picture always, night or day".

So, is the little red round sensor in the middle of the cabinet under the picture tube for the Magnalux system then? 

I read three times before what I shared just now made any sense.  Videomatic is included in the circuitry of the TV, just where we shall find out one of these days.  Sure is a lot of "automatic" stuff on one of these TV's.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on June 27, 2018, 02:52:05 AM
      videomatic might be automatic fine tuning  which was actual AFC and almost a necessity on a color set. the black and whites might get away with preset fine tuning which had 12 little gears and eccentrics around the dial and remembered your fine tuning adjustment for each channel individually.

       If you shine a flashlight on the light sensor and the picture  gets brighter then that's definitely the automatic brightness control.  but the remote ultrasonic sound pickup is also a small round thing on the front of the set somewhere. I guess you have to trace the shielded red wire from the back side remote chassis. It might be under the speaker grill cloth since it doesn't need to let light through like the room light sensor.


          chromatic optical filter might be a sheet of grey tinted glass bonded to the picture tube glass. supposedly it improves contrast in a brightly lit room by making reflected light make a two way trip through the tinted glass and therefore be attenuated twice while the picture off the screen only makes a one way trip through the tinted glass.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 27, 2018, 08:36:09 AM
You may have nailed Videomatic, Ed.  There is no fine tuning knob on the channel knob.  All the normal controls are placed on the back of the cabinet.  I can't imagine an old black and white all-tube TV that would not run vertically and/or horizontally when you start it up.  Or not need some other adjustment before you could watch it. 

Vidoematic and Magnalux seem to me to be fairly advance features for the time.  The old TV guys have little good to say about Magnavox TV sets in general.  Any idea why that might be?  Is there something inherently wrong with Magnavox TV or are they just not an RCA or Zenith?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on June 27, 2018, 12:47:07 PM
   I don't know why I've only seen 2 Magnavox TVs in the flesh ever, one an early 50's chassis only with no audio circuits that probably slid into a radiophono as an option. It seemed rather well designed and constructed to me. The chassis metal was shiny and smooth, the 5U4 plugged into the top of the large power transformer, it had a 17" rectangular picture tube fastened to the chassis 3 or 4 IF stages, plenty of good circuits, and actually worked well and had a good picture. The other was a roundie mid sixties 21" color console that I was always adjusting for my friends parents and was on all day long and had a dimming picture tube. It had a lot of automatic adjustment features with extra pushbuttons to optionally enable or disable them, if I remember right which probably didn't help their reliability, and I seem to remember noisy tuner and switch contacts, but that house was a dusty one and had a cat and a dog too.
          The stores that carried Magnavox in the Baltimore area were stores that had furniture, clothes etc and appliances wasn't their main thing and their service departments maybe just never saw many Magnavox TVs to get really used to them like more commonly sold RCA, Zenith, Philco, Admiral and other medium priced brands. I worked in the parts department at Luskin's discount appliance store for 9 months, so I never saw a Magnavox chassis being worked on service call guys made small adjustments in the home and dragged in the chassis for the real repair problems. They were used to the most common models and didn't like working on the seldom soldones. They probably wouldn't have liked Magnavox just because they never would have seen many, I=f we carried them
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Motorola Minion on June 27, 2018, 01:26:26 PM
Magnavox B-W TV's of the late 50's thru 1960's were good, not great though.

The build quality was good, but TV design was fair at best. I had one from 1956, 1958 in my former collection.

Nothing on the TV chassis was hard to fix, and they kept playing when you nailed it, but the picture was never Zenith quality.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 27, 2018, 02:30:58 PM
I am incorrect in my belief that Magnavox TV was a Zenith clone.  I have never in my life seen a Magnavox TV up close and personal.  The picture that was posted earlier looked good to me.  If mine will produce that good of a picture, all will be well.  Thank you both for your input. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on June 27, 2018, 06:11:47 PM
      Most of the TV makes seemed to vary hugely in quality and design depending on the model and depending on the era they were built in, from what I've seen. Even the last of the tube era, when they were all series string tubes on a circuit board and were all duodecar 12 pin compactrons could be really nice and sturdy and reliable or doomed to fail. 
     The big decider would be whether they had the quality sockets with the semi-circular pinchers or the parallel flat bladed sockets that always seem to get loose and intermittent. Also making a big difference was what kind of tuners were used--whether they could come out of the chassis with a plug and one screw and had turret button contacts you could wipe directly  or the worst would be non removable cover shields and the wafers that couldn't be cleaned except by spraying stuff. Having high wattage resistors soldered to the circuit board was bad---they would soften the solder joint with their heat. Having the filter capacitor right next to the high wattage tubes instead of ina cool location was another thing I'd see a lot.
         You just never knew what you'd see until the back came off.  My favorite was the Zenith black and white hand wired chassis of the fifties and early sixties. They did everything right--turret tuners that slid out of the set, the good tube sockets, no circuit boards, a brilliant circuit, 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on June 27, 2018, 07:27:53 PM
I have a friend that is into Zenith.  It's what he grew up with so that's most of his collection.  A couple of TV's, several floor radios, and some record players.  He also has some odd Zenith color sets.  Most of it does not work as he doesn't seem to ever have time to work on them.  Maybe that's because he is young with 3 little girls.  They keep him busy.  :)

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on June 27, 2018, 09:31:55 PM
      videomatic might be automatic fine tuning  which was actual AFC and almost a necessity on a color set. the black and whites might get away with preset fine tuning which had 12 little gears and eccentrics around the dial and remembered your fine tuning adjustment for each channel individually.

 

In storage I've got a 1960s Philco "suitcase" portable that used a pneumatic (squeeze bulb on a tube) channel-changer--a sort of cut-rate remote control.  Problem is, it doesn't seem to have a channel-specific fine tuning arrangement like you describe.  So you can change the channel with the squeeze bulb but then you've got to get up and fine tune it anyway.  I kept the TV mostly because I thought the pneumatics were cool.  And now it's "vintage."  So am I.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 27, 2018, 11:39:35 PM
I have been studying the remote control system.  I'm beginning to get a handle on how it works.  Do any of you guys know if Magnavox ever used an instant-on feature in black and white sets?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: walyfd on June 28, 2018, 06:46:47 AM
I used to work with a guy who retired from Thompson Electronic ln Scranton that made tv's for RCA.  He said they also supplied Magna vox and their build quality wasn't as good as the ones that went in RCA sets.  I'd say this was more in the 70's and 80's...  unfortunately he died and the story went with him...
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on June 28, 2018, 07:27:16 AM
         I think the plant for Thompson was somewhere in Tennessee. Thomson was a French company, I believe, and the only  connection to RCA or Magnavox was the name.
          It really annoys me how an old name can be bought and applied to a product from another manufacturer with no connection to the original make. That's one reason I like to find old stuff and try and get it working. A mid-fifties General Electric refrigerator really was made in Bridgeport Connecticut, just like the metal plate on it says.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: amglow on June 28, 2018, 08:11:23 AM
Greg,
Attached is am image of the Ultrasonic Remote Mic location in a 1967 Magnavox Imperial stereo console.  It's inside the right channel speaker enclosure near the top, hidden in the grille cloth, as you surmised.  I'm not sure if that would be the same for your stereo theatre, but I believe there is a high probability that it is in a similar location.
Quote
Magnavox would hide things in the grille cloth.  There should be a pilot light in the grille cloth (maybe) on the end of the cabinet with the "Magnavox" script on it.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 28, 2018, 09:24:23 AM
I believe I have located the mic on mine.  I posted a picture of it earlier.  Yours is a little higher up in the cabinet, but they are basically in the same area of the cabinet.

I've about done all I can except read and research until I get the instrument on the bench. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: voxACthirtee on June 28, 2018, 03:11:20 PM
A couple things....
The stereo theater was a high end unit, i have "owned" 2 different unrestorable units.One was a 419, one was a 420, neither had the remote.
1) Both had higher end speakers - on mine, one had real Jensens, the other real Oxfords.    Not a silver/grey Mag version. Real blue Jensens and real Beige(?) Oxfords.
    So in all likelihood there will be NO "232" speaker code on the woofers    220 for  Jensen, 465 for Oxfords and 137 for CTS if thats what you have.    They were all of similar quality
2) I can't remember it now, but both 27" CRT were non Magnavox per the manufacturer code.    I want to say you were right and that they were Zenith made...yours will have a code on
    a sticker on the CRT
 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 28, 2018, 03:45:57 PM
Mine has a rebuilt/replacement CRT in it.  The codes on it might prove interesting.  My thinking on the relationship between Zenith and Magnavox was their vertical TV chassis with the HO tube in the same place and their "sharing" of components, most notably remote control systems.

The big speakers in mine are coded 137, C.T.S., Chicago Telephone Supply.  Your input on the speakers being high quality is appreciated.  Do you have any of the parts from yours left?   
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on June 29, 2018, 12:12:57 PM
This thread has me curious on a few things so I will take a trip to the barn and have a peek at Greg's ST again.  Greg, is this driving you nuts not having your new toy?  It would me.

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 29, 2018, 02:28:58 PM
Share your curiosity, Bill.  We are all here to maybe learn something, whether we want to know it or not..... ;)

Yeah, it would be really swell to be able to walk out to the shop and look at something when my curiosity gets piqued.  You could wear a path to the barn answering all the questions I have right now.  I'm making a list...... ;)

RCA/Thomsen had a plant on the NE side of Indianapolis, on North Shadeland Avenue.  I don't believe they actually built TV's there, but it was their headquarters for a time.  There was a big RCA plant in Bloomington, where they did build TV's.  A customer of mine bought a new school bus every few years and hauled riders to RCA for several years.  My mom worked at Sarkes Tarzian, also in Bloomington, making tuners, (she wound the Channel 3 stick for YEARS).  RCA was the enemy as far as "Sarkie" was concerned.  RCA, at least while mom worked at ST, did not buy their tuners from Tarzian. 

Since my mom worked at Sarkes Tarzian from 1958 to 1970, and since Magnavox was a Sarkes Tarzian customer, I wonder if the tuner in the Stereo Theater had its Channel 3 stick wound by my mom.  She could still rebuild a turret TV tuner when she was in her senior years.  Local TV repairmen would bring TV tuners to my mom to be rebuilt.  She would do the physical work on the kitchen table at home, then take them to work in her dinner bucket for any "technical" work they might need that she did not have the equipment for at home. 

Sarkes Tarzian, Inc., does not appear to have an EIA code.  Wonder why not?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: voxACthirtee on June 29, 2018, 04:15:42 PM
Sorry, no parts left. I think i found an antique TV group on FB and donated the TV parts to a semi local guy.I grabbed the White peeling one that was in new Jersey a couple years ago.I know it was discussed here. After it sat for months and months with no takers, i took....Ran into another half destroyed one after that.
I think i'm probably wrong about your CTS speakers. I went back and read more of this thread and realized you have 12's. Both of mine were 15's. I'd guess you have the regular grey CTS speakers.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 29, 2018, 05:02:44 PM
The antique ivory one in New Jersey would have looked dynamite in ebony.  Had it been closer, that is.  That one was a 419, as I recall.  I just thought you might have held onto some parts.  Thanks.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on June 30, 2018, 04:23:01 PM
My mom worked at Sarkes Tarzian, also in Bloomington, making tuners, (she wound the Channel 3 stick for YEARS).  RCA was the enemy as far as "Sarkie" was concerned.  RCA, at least while mom worked at ST, did not buy their tuners from Tarzian. 

Sarkes Tarzian, Inc., does not appear to have an EIA code.  Wonder why not?

I've got a Sarkes-Tarzian tube based FM table radio around here somewhere--a find by my grandmother  in Alabama, who always saved radios for me.  I'll see if I can dig it out and look for codes.  It was essentially an AA5 for FM.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 30, 2018, 05:35:31 PM
I'd like to buy a Sarkes Tarzian radio one of these days. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on July 01, 2018, 04:35:35 PM
Today was trip to the barn day to take another peek at Greg's ST.  This time I took a flashlight with me and I think I have some answers.  The mic pickup, for the remote, is in the RH speaker grille next to the horn.  There is small hole where it mounts.  It's lead goes to the remote chassis.  The round, red, thingy below the picture tube is the auto light sensor and it's lead goes to the RH side of the TV chassis.  Below that is a small hole drilled in the cabinet, maybe about 1/8 inch.  I put the flashlight behind it and it shows red.  There is a socket/bulb there so that must be a pilot light.  The little channel box in the RH lower corner of the screen surround is to show channels.  The round disk behind it does have numbers and a socket/bulb to light it.  It is cable driven from the tuner up top.  The cable looks like a car speedo cable. 

I also found a dime so you made some money on this deal Greg. ;)  I left it where I found it.  There is also a little plastic bag next to the dime with some stuff in it.  I think it's antenna related. 

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 01, 2018, 11:05:00 PM
You have confirmed our guesses, Bill.  Thank you for taking the time to do that.   :)

You have also found the pilot light.  I saw the wires coming off the amplifier chassis, but they went under the TV chassis and disappeared.  You found the light.   :)

The channel indicator in the corner of the CRT mask sounds like an interesting contraption.   I assume one needs to "time" the upper indicator to the one in the CRT mask.  Earlier, you mentioned a paper pasted to the cabinet that gives details for such an operation.  Did you find a lighted indicator on the dial in the tuner compartment?

I'm having a dickens of a time coming up with a Sams for this thing.  I will need one for the radio tuner, one for the TV chassis, one for the amp and one for the remote.  Sams #591 is the closest I have come up with.  I'm told I may have to settle for "close" as "exact" may not exist.  No such thing as a Sams for the entire Stereo Theater.  The paper diagram of the stereo pasted to the cabinet may prove more valuable than normal.   
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on July 02, 2018, 06:10:35 AM
I forgot to look under the hood at the channel selector.  Sorry!  I wonder if a Magnavox dealer would have had a full schematic for the ST?  I can't imagine Magnavox didn't provide one, but you never know?

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 02, 2018, 07:27:46 AM
If I were to offer a guess, I'd say they did.  There is one for the Concert Grand, and I'm willing to wager that was not the only one they printed a full manual for.  Finding one will be the next thing.  There was a member on ARF who was helpful with that type of documentation, but I have not heard from him in ages.  Sams printed Magnavox documentation per the chassis model number.  I will have to go that way until I find something more complete.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on July 02, 2018, 08:07:01 PM
When the time comes I'm sure the documentation will be available. It seems to work that way for me anyway.  Pick up day is getting close.   :)

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 02, 2018, 10:41:48 PM
There was a member on ARF who was a Magnavox guru and was helpful when it came to documentation.  I have not seen him on the forum for some time.  I reached out to him to see if he could help.  I have not heard back from him, and, in fact, he has not picked up my message. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 14, 2018, 09:20:54 AM
I now officially am in possession of my Stereo Theater.  I don't have it unloaded yet, as I need to find a couple strong backs.  Bill was right.  This thing is HEAVY.  Heavier than my Concert Grand.  The CRT must weigh 100 pounds by itself.  I hauled my Concert Grand up from Fort Worth on I-49 thru Oklahoma, which I thought was the roughest road on the planet.  I hauled the Stereo Theater on US 31 in Michigan.  If it ever works, it will be a credit to the women in the cornfield in Indiana who put it together.  I drove 1132 miles to get the Concert Grand.  I drove 1464 miles to get the Stereo Theater.  The Stereo Theater only moved about an inch from where we put it in the trailer. 

Bill is the hero in this project.  There are a few surprises I'll share as we go along.  This Stereo Theater definitely needs the "touch" and some TLC.  I'm thinking it will build out fine, pending checking a couple things.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 14, 2018, 10:19:21 AM
    I pity the poor stereo theatre. Sixty years of peace and quiet on the same spot in the carpeted living room and then suddenly a thousand miles on a super-bumpy road. Quite a shakedown test.
     I understand companies used to ship a prototype unit to a distant location by truck and then back to themselves as a realistic test for reliability instead of putting in hours on the vibration table.
      I notice everyone comments on the extra long wiring bundles connecting two internal units only inches away. Is that because Magnavox tried to use various basic chassis in as many different models as possible so they allowed extra lengths so as to reach the destination no matter what the layout was in a new model being designed ?
     
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 14, 2018, 11:00:30 AM
I don't hear any broken glass clanking around.  I found a dime and a bag of screws on the floor of the trailer, but that was it.  My little Wells Cargo trailer, "Myrtle", rides pretty smoothly, apparently.  It hauled my Symphony and Imperial to Arizona, thru Oklahoma City.  The wheels of the trailer were in the air more than on the ground.  Oklahoma City has THE roughest roads anywhere, even Chicago, and that is saying a lot.  Both of them survived just fine.  We wrapped the ST cabinet in blankets then shrink-wrapped it.  I moved the cabinet around until the casters were not parallel with the sides of the trailer, and it never moved.  This Stereo Theater has been somewhere where it was abandoned for a time.  Lots of dust and dirt.  The dirtier they are, the better they build, in my experience.  Dirt preserves them.  I don't see any mouse pee or signs of moisture, so all should be well as far as that's concerned.  It has the only set of working casters I own.  These, all four, actually roll in the same direction.   ;)

Magnavox built their instrument by module.  They mixed and matched components, depending on what you wanted.  They built their stuff to order.  Their wiring mess is legendary.  They used paper hangers to suspend the wiring semi-neatly, but service personnel and old age have rendered those useless, so the wires dangle wherever they please. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: danrclem on July 14, 2018, 02:57:07 PM
Glad to see that you got it home safe and sound Greg.

When you get it running you need to invite us all over on a Sunday evening to watch Walt Disney and Bonanza.  I call dibs on front center sitting on the floor.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 14, 2018, 03:33:11 PM
You got it! 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: walyfd on July 14, 2018, 04:13:44 PM
Sounds like it would've been easier to just buy the house and you move to the maggie!!!

I must say I'll miss the thread about the quest but glad you got one.

Now I have to find a Fisher Living Theatre... 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on July 14, 2018, 04:26:48 PM
I told Greg and Mari that they could stay with me but their adventure took them farther north.  They picked up the ST as they headed home.  I included a few more items, kind of a surprise.  Greg will fill you in later.   ;)

I get the spot on the floor next too you Danny!  We need popcorn as well.

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 14, 2018, 04:32:21 PM
And root beer!   :)

The adventure of the search was exciting, but the restoration should be more so.  I'll need lots of help and I'll make lots of mis-steps.  There is unchartered territory in this ST.   :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 15, 2018, 08:59:09 AM
Before I make reference to this stuff and nobody knows what I'm talking about, I'd like to mention this.

There was some "optional equipment" included in the Stereo Theater transaction.  Apparetly, an Astro-Sonic Stereo Theater, with which I was familiar, was parted out.  I've seen dates of 10-65 on different items, so we'll say it was a 1965 Stereo Theater with Magnacolor.  It was a roundie and had a fairly significant cataract on the CRT, but was otherwise nice.  I now own the tuner assembly, model 402-20-20.  It is a six-knobber, so it is close to top of the line.  I'm thinking either the 75 watt version or the 100 watt one.  You Astro-Sonic guys jump in here and bail me out if you'd be so kind.... :-[

Also included were both the horns and the 15" woofers.  And the remote control chassis.  AND.....TWO remote control units, with brackets!  And all the knobs from the stereo and the TV.  And the trim bezel for the tuner.  I looked the tuner chassis over pretty well and came to a conclusion.  I need to take a more open-minded attitude toward the Astro-Sonic series of instrument, particularly the early ones.  This thing has point-to-point wiring, has Nichicon capacitors and looks well-built.  This thing is not the junky PCB contraption I expected.  The tube instruments did not have Nichicon caps.  Of course, this one could have been recapped sometime in its life, but I don't see evidence of that.  The 15" speakers have "719" codes on them, so they were made by Carbonneau.  Since I'm going to have the grille cloth out and off, my Stereo Theater may gain a pair of 15" woofers during its restoration.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 15, 2018, 12:09:59 PM
The pictures of the top of the cabinet on my ST.

The finish has had a hard life on the top for some reason.  In digging around and using Windex on the cabinet, I'm beginning to believe that the dark material you see is not finish, but is just dirt.  The lighter part is the finish, but is terribly dry.  I was prepared to refinish the entire cabinet, but now I'm beginning to wonder if a good cleaning and some orange oil might put most of the cabinet in good shape.  I believe it more expedient to replace the grille cloth.  The wife does not like it, the ends don't match the front and it's dirty, so there you go. The sliders are beyond hope to save the original finish.  It appears somebody used lacquer thinner in an attempt to clean the sliders and removed the finish.  Those and perhaps the top rails of the cabinet will need help.  The wood is an open-grain type "Natural Walnut" and has a semi-dull type finish.  Not like the lush, oily finish typically found on a Magnavox cabinet.  We'll see as the project progresses how this all plays out.

The sliders on top and the sliding doors on the front are missing much of their felt bumpers.  The sliding doors in front run very roughly in their tracks.  Methinks the felt bumpers on the bottom of the doors are gone or in bad shape.

Help is coming tomorrow morning to help unload the ST and put it up on the bench.

This is like Christmas morning!  I have waited a long time for this occasion.  I'm thrilled to have this old ST.  Words are not adequate to express how thrilled..... :)

I've been tinkering with the remote control chassis that came with the ST.  What an ingenious Rube Goldberg contraption that is!  When you press the button on the remote, a relay closes, pushing down on a little ratchet mechanism, turning a function switch, causing something (hopefully) to happen.  Ions more simple than the Phantom Control in the Concert Grand.  The remote controls volume in three or four stages, on and off, and changes channels.  You can vary how loud the volume within those stages are with the main volume control.  Quite the setup.   :)

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on July 16, 2018, 07:42:42 PM
Hopefully it's now unloaded and on the bench and the fun begins.  :)   Extra goodies are always nice.  ;) 

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 16, 2018, 11:23:17 PM
It is unloaded and up on the bench.  It arrived in fine fettle.  The only thing that moved was the sliders, both top and front.  I have started my preliminary inspection.  Nothing really out of the ordinary at this point.  There has been some sloppy work done on this thing at some point.  The rectifier socket was replaced, is the wrong configuration and will not fit the hole properly, so it is only held on with one bolt.  The rectifier sits with a list to starboard.  The amp chassis, a model 9302-10, only has one of its four retaining bolts in residence.  The MPX chassis only has two of its four.  There is no wiring retainer in residence anywhere in the cabinet.  Most of the bolts are missing from the back and the shield on the IF strip is missing from the radio tuner.  Many, if not most, of the tubes have been replaced.  There are at least three Radio Shack Lifetime tubes in the amp.  I am going  to check all the tubes, make sure they are in their correct locations, and check every inch of the wiring for condition and correctness.  Then I will use the dim bulb and Variac and power up carefully.  I want to test the 27ZP4 picture tube to make sure it is good.  I got my B&K model 445 picture tube tester out today and will read up on how to test a picture tube.  Never done one in my life that I remember.  I have had the picture tube tester since 1987 and have never used it.  The picture tube is Magnavox branded, EIA coded 274, with is RCA, and date coded for the 25th week of 1962, consistent with other codes we have found.  There was some speculation that this might be a replacement tube, but it appears to be the original. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on July 17, 2018, 10:18:55 AM
Step one complete, unloading and inspection. Now the fun begins.  ;)  Are you spending the day with your new toy?

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 17, 2018, 01:41:17 PM
I am!  In my newly air conditioned garage!   ;)

Progress is being made.  One step forward and two backwards at this point, but that is normal in this early stage of the restoration process.  I know that the power transformer in the amplifier has been changed at some point.  So has the rectifier socket.  I'll redo that job.  The filter caps are all original.  I found a socket for the damper tube in the TV chassis that does not look very good.  I'll replace the socket and see if I can figure out why that happened.  The tube tests good.  The TV comes out as a unit, just like I figured.  Not easy, but doable.  Also the shelves the components set on in the bottom of the cabinet are particleboard.  They are held in with screws and not glued.  I believe I can take the particleboard out and replace it with hardwood plywood in grand Magnavox tradition.  Testing the CRT is the next step.  I'm going to power up the amp with the rectifier out and see what that does.  I'll have to recap the power supply before I can apply B+ to the chassis.  The Radio Shack Lifetime tubes in this amp are RCA coded.  The output tubes are Hitachi coded, just like factory tubes.  If those test good, I might keep them.  A couple of hours ago, I began to wonder if I was in over my head.  This "gloriously complicated" restoration will be bringing this thing back from the brink if I'm successful.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on July 17, 2018, 04:09:53 PM
SEE!  ;)

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 17, 2018, 04:46:23 PM
More baby steps of progress.

The picture tube checks right on the edge of good.  I let it "cook" for a few minutes at 8 volts and it came right up.  The life test is not so good, so it is fair to say the CRT has lots of hours on it.  I'm going to leave it alone for now and finish the rest.  Then we'll worry about the CRT.  I'm not opposed to using a brightener for the short term if necessary.  I have a Silvertone TV in my parts that might yield a good picture tube.

I believe, in this case, it might be prudent to recap everything totally before I apply power to anything. 

I've been cleaning and figuring out what everything is.  The big bunch of caps on one of the supports we talked about are actually the crossover networks for the speakers. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 17, 2018, 10:56:30 PM
This instrument was alleged to have a "bad hum" in the audio.  I have found certain conditions that may lend credence to that claim.

*The power transformer, rectifier, rectifier socket and nearly all the tubes in this instrument have been replaced.  Every capacitor, electrolytic or otherwise is original.  The resistance measured between the rectifier cathode and the positive end of the output filter cap reads 146K ohms, indicating severely leaky or close to shorted filter caps.  I'd like to see the high-100's K ohms here.

*The common connection for both channel speakers terminates at the amplifier.  I found the common for the Channel 1 speakers connected to the hot terminal for Channel 2 speakers.  Connecting the common and hot terminals together could cause a nasty hum, and put the output transformers in jeopardy.  I need to check those next.

*I have not found the cathode by-pass resistor.  I do not have the exact schematic for this amp, but all the other 9300 series amp schematics I have show a cathode bypass resistor.  If this one is missing or was removed, that could cause a bad hum and again, put the output transformers in jeopardy.  All the tubes but one in the amp and many in the TV chassis are Radio Shack Lifetime.  Somebody has been seriously throwing parts at this thing.  I have only found two tubes, one in the TV chassis and one in the tuner chassis that are still Magnavox branded.

I am having trouble finding the schematics I need for the various chassis in this instrument.  I need to call Steve Johnson and see if he can straighten me out.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 18, 2018, 07:03:56 AM
The 9300 series amplifier schematic that Pat posted to the Downloads section will work for my amplifier.  It has changes between models listed, something I desperately needed.  I was reading the number upside down, but I believe the tuner model number I'm looking for a schematic for is 77-03-11.  This is a nine-tube version of the 5700 series tuner without the shield over the IF strip.  I can't find reference to that model anywhere.  I may be in the market for a good 27ZP4 if anyone has one or knows who might have a good one.

I also discovered the difference between the various amps in the 9300 series.  The 93-01 and 93-02 amps have the balance control on the amp chassis.  The 93-03, -04, -05, 06 have the balance control in the tuner.  The -10 suffix usually refers to an amp in a Stereo Theater.  I'm glad to know this.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on July 18, 2018, 08:56:37 AM
I like baby steps, that means progress.  :)  And thanks for the info on the 9300 series amp.  Mine must be an 01 or 02 because I don't have a balance control at the tuner.

I hope everyone is as interested in Greg's new toy as I am.  It was a privilege to see the ST before restoration. The look on Greg's face when he saw it was like a kid at Christmas. So excited.  And with this being the first Stereo Theater (at least I think this is the first ST) being documented on this forum, it will be fun to hear all of your comments, questions, and support.  Keep those baby steps going Greg!

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 18, 2018, 10:13:46 AM
Bill, pull the knobs off the treble and bass controls on your stereo.  One of those shafts may be hollow.  If it is, there is a good chance the balance control is in the hollow shaft.  You need my magic Snap-On screwdriver to adjust that balance control.  Long, skinny "minus" shaft on the screwdriver.  If the balance control is on the amp chassis, there may be two black knobs on the chassis.  One, in the proximity of the choke will be the hum control.  The other one, under the 6EU7's, will be the balance control, marked "BAL".  You are supposed to set the balance by playing a mono record, and with AC voltmeters connected across the bass speakers.  You are supposed to have a test record made especially for that purpose, but playing a mono record will get you to the same place.  You set the control for the same output to both channel speakers. It sounds more complicated than it really is. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Motorola Minion on July 18, 2018, 11:25:39 AM
I have not finished putting together my 1962 Normandy with that 93-series amp and 57 tuner. I am hoping to make mine a better amp before I do. So...

I read some of your other posts about the 6EU7 being troublesome but otherwise electrically the same as the 12AX7.
Would you consider replacing the 6EU7 sockets (there is one in the tuner as well) and rewiring to use the 12AX7 instead?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 18, 2018, 03:57:52 PM
I sure have considered converting from 6EU7 to 12AX7.  My understanding is that new 6EU7's are now available, so, if that is true, I probably won't go to the trouble.  I do not have any left in my stash.  My hesitancy is due to my belief that the Magnavox engineers were lots smarter than I am.  They used the 6EU7 for a reason.  The reason I would consider swapping to the 12AX7 is more due to supply reasons than technical ones. 

I'm not sure there is much you can do to make a 9300 better.  It is already one of the best amps ever built my anybody.  The one I have in my ST has been thoroughly hacked, so it will need more TLC than normal to bring it back.  I just make sure each component is 100%, particularly the caps, the 220K grid resistors and the cathode bypass resistor. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 18, 2018, 04:33:57 PM
I have spent today's session cleaning and straightening out wiring.  What a rat's nest.  There are wires wrapped around each other.  Shielded wires wrapped around power handling wires.  No wonder it had a hum.  I'm surprised it did not have a fire.  I want to check each wire, clean it, route it somewhat neatly before I apply power.  I'm taking my old sweet time and enjoying every minute of it.  Most of the wiring is out and laying on the bench.  I'm taking lots of pictures and tagging everything. 

The bottom of the cabinet is open under the TV.  The shelves on the ends of the cabinet that hold the stereo components are made of particle board that is disintegrating from old age.  I noticed today that under the picture tube, the particle board is actually sagging, so it will have to be replaced for certain now.  I was undecided whether to replace it or just seal it with shellac so it would not deteriorate further.  After I remove the end speaker board and the amp so I can see better, I can better figure out how to get the particle board out and get the new plywood in.  It will be a tricky job, that's for sure.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on July 18, 2018, 09:33:23 PM
Thanks for the tip Greg, I need to check for the balance control location.  That stereo is next on my list of things to do.  Changing out the bottom board sounds like a real fun thing to do.  ;) 

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 18, 2018, 10:48:40 PM
By the way it looks, after I get the screws out (doable, I believe) I believe I can bring the shelf up in the rear and squirrel it out from under the front panel.  The job will only be possible after the CRT is removed.  There is too much risk of damage to the CRT otherwise.  My plan is to borrow a "porta-power" and use it to jack up the upper part of the cabinet so I can remove the particle board and insert the plywood.  1/4" is about all I need for clearance.

Bill, your "Mystery Magnavox" is a five-knobber as I recall.  I'd wager that the balance control is in the hollow shaft of the bass control.  The power switch is probably on the treble control.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 19, 2018, 01:16:29 AM
           Having that common 100 ohm cathode bias resistor for all 4 6BQ5 tubes might be the cause of some of your hum because the tubes have such high transconductance (I think 11,000 micromhos, just like an EL34) that a single tube is more or less at the mercy of the other 3 tubes current draw. The least variation in tube brands or age will  give wildly different static currents. A 1 volt change in bias voltage will cause an 11 milliamp change in current. Just for safety sake after having one power transformer replacement and rectifier socket replacement, you might consider using 4 separate 400 ohm cathode bias resistors with 4 separate bypass capacitors. The currents will be much better equalized and you can make 4 separate voltage measurements across the resistors.
       Magnavox probably had a tube matching test jig to select 4 similar tubes for each amp to make up for a common cathode resistor. A lot of the power supply ripple cancellation of push pull operation is lost when the tubes have  wildly different mutual conductance from each other. The better tube will overheat and maybe get a screen grid to control grid short which could have caused the original meltdown. I think Amperex recommended 100 kOhm grid resistors maximum on fixed bias 6BQ5s, as well as series grid parasitic suppression resistors of 10 kOhm at each tube socket so the tubes wouldn't take off at 100 Megahertz or so due to wiring capacitance, especially with four output tubes near each other, just like all those plate coils and 100 ohm resistors when 4 or 6 6V6s are in the older Magnavox bi amp circuits. It's almost impossible to know if the tubes are having parasitic oscillations because it won't show on most oscilloscopes or AC voltmeters at those high VHF frequencies.

      More in another post, this computer has a timeout on it.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 19, 2018, 01:50:37 AM
              Incidentally, one of the few audible indications that the output tubes are in a parasitic  oscillation condition is raspy sound and a hum or buzz in the speakers which might suddenly go away or get louder when various voltmeter measurements are attempted . A 10kOhm or so resistor in series with the meter probe soldered directly to probe tip  will ensure that touching the meter lead to the circuit won't start it into oscillation.  6BQ5s are one of the most wiring-critical tubes because they have short internal connections and no phenolic sockets like 6V6s to have RF losses plus high transconductance all of which makes them easily oscillate especially when several are in parallel. The more tubes in parallel, the easier the oscillations can start and a uniform wiring layout can make it worse because the lead lengths are equal which favors a particular frequency.

          I will soon be getting my  aunt's 61 Magnavox French provincial which I think has the 9300 amp chassis and the first thing I will change is to 4 400 ohm resistors and adding 10 k grid series resistors and 470 ohm screen grid resistors directly at the sockets as recommended by the Amperex tube manual. I apologize for sounding like a broken record on this point but it's easier to add the proper resistors at the sockets than attempt to measure for RF in the audio circuits. Sometimes it only oscillates intermittantly during current swings when audio is applied to the circuit and not when no audio is applied. Having 4 new tubes installed means someone was hoping to cure a problem years ago, after the transformer and rectifier were replaced years ago.

          good luck !!
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 19, 2018, 02:21:27 AM
I'm back. This computer timing out is driving me crazy. 
      I see that the top 6BQ5 has a 470 k ohm grid resistor and the bottom tube has 220 k .   That makes it even more important to have 4 separate cathode resistors  100 k is the maximum for fixed bias which is what one common resistor essentially is for 4 tubes..  470 k is the maximum allowed for cathode bias .d Did you ever locate the 100 ohm 5 watt resistor for the cathodes of the 4 tubes. ?  Maybe soldered directly to the electrolytic lugs ? 
         Sounds like someone was experimenting with moving wires around, maybe while listening for a reduction in hum ? 
            Gotta log off again or I lose all this typing again
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 19, 2018, 09:19:10 AM
I appreciate you jumping in here, Ed.  I have long wondered why I find so many cathode bypass resistors burned to a crisp in Magnavox amplifiers.  I have had four out of my six instruments.  The one in my Imperial bi-amp chassis was burned in two.  What you are saying makes sense and fills in the blank somewhat.  I'm not sure I follow why the resistance needs to be increased from 100 ohms to 400 ohms.  And do I need to separate the grids when I put in separate caps and resistors?  Electrical engineering is not my strong suite, so I appreciate someone with that knowledge.  My guess on the transformer replacement is that somebody was throwing parts at this thing for who knows what reason.  This amplifier is the MOST hacked electronic item I have ever messed with.  It is a mess.  All those parts thrown at this poor little amplifier and they left the filter caps original.  They are just north of dead shorted. 

My plan for this amp is to verify correct wiring to start.  Then I'll restuff the filter cap can, measure and probably change 80% of the resistors, all the coupling caps and make your recommended mods to the cathode circuit after I get my head around why I need to increase resistance from 100 to 400.  I typically increase the capacitance of cathode bypass caps and the output filter cap.  Instead of 40uf, 30uf, 30uf and 10uf in the filter can, I'll do 47uf, 47uf, 47uf, and 24uf.  And increase the voltage ratings from 450 to at least 525.  The Radio Shack 6BQ5 tubes currently in this amp are all over the place in transconductance and output.  None of them check shorted, but I have not had them hot either. 

I have not found the cathode bypass resistor.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 19, 2018, 11:54:51 AM
I think I see what your thinking is on putting 400 ohm resistors on each tube.  The cathodes are essentially connected in series as far as the cathodes are concerned.  So four 400 ohm resistors connected in series would be 100 ohms at each cathode, correct?  Then you are saying that instead of a 470K ohm resistor for all four tubes, one would be better to have a 100K ohm in the grid circuit for each tube.

Since I am a firm believer that the 9300 series Magnavox amplifier is one of the sweetest amplifiers ever built, you can understand my hesitance to change much.  I believe I can see the benefit in your suggestion.  I'm wondering if adding a separate cathode cap and resistor in the bi-amps would be beneficial for enhancing bass response.  Weak bass response is not a concern with the 9300 series amps.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 19, 2018, 08:14:32 PM
Before I forget..... :-[

There has been considerable discussion about using Go-Jo hand cleaner, without pumice, and 0000 steel wool to clean old radio cabinets.  I have used Go-Jo with a cloth, but was not convinced that steel wool was the right thing.  There is a spot on the sliders of this ST that I am going to refinish, with nothing to lose.  I tried Go-Jo and 0000 steel wool.  It took the finish right off, down to bare wood.  I tried it with just a rag instead of steel wool, and that worked better.  You need to be careful using Go-Jo on finished wood where the finish is oil based.  If the finish happens to be thin, like this was, Go-Jo and steel wool are far too aggressive.  I like Go-Jo to clean lots of things, but be careful.  You can do more damage than good sometimes.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 19, 2018, 09:51:41 PM
I needed to bone up on what I did not know about cathode bias.  There are three considerations on this amp that I needed to look at.  This is one of the sweetest amps ever made.  I did not want to alter its "personality."  I have been looking for a cure for why cathode bias resistors in Magnavox amps are frequently found burnt or overheated.  And how to adjust the hum control in this amp which biases the cathode circuit with absolutely no value on the schematic as to what the cathode bias voltage should be.

The spec for the cathode bypass cap is 20uf at 25 volts.  If I connect four of those in series, I end up with a 5uf value for the cathode bypass cap.  That will absolutely kill the bass.  That means I need four times 20uf, or 80uf on each cathode in order to have my 20uf cathode bypass cap value. 

The cathode should be biased positive relative to the grid.  The grid acts to suppress electrons flowing from cathode to plate, thereby limiting plate current.  The cathode bias resistor regulates the bias voltage to the cathode.  I can see increasing the value of the bias resistor from 5 watts to 10 watts in an effort to prevent burning up the resistors.  It is obvious that they carry more current than they are designed for.  Perhaps that is the secret.  Putting individual bias resistors and bypass caps on each cathode is overkill, as you stated earlier.  My fear is changing the personality of the amp.  The jury is out on my decision, but this is how my thinking is at this point.  Put it back like it should be and perhaps increase the value of the cathode bias resistor. 

What if I used separate bias resistors for each cathode, but kept a common bypass capacitor?  That would take care of the bias situation without changing the personality of the amplifier, would it not?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 19, 2018, 11:13:25 PM
I also need to thank Larry H. for providing some much-needed and much-appreciated information that I had been looking for eons for.  Thanks, Larry!   :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 20, 2018, 08:11:00 AM
    Well don't feel too bad not being familiar with suppressing spurious oscillations in the power tubes because the amplifier designers didn't seem to be either. Looking at circuits with similar wiring layouts and identical output tubes, you can find resistor values as low as 22 ohms and as high as 47,000 ohms in the control grid leads, and 10 ohms to 4,700 ohms in the screen grid leads. Either someone is using their own pet formulas or they're just increasing the value until they are sure it can't oscillate and then including a generous safety factor. Or no safety factor, because so many circuits use no resistors at all, or just screen grid or just control grid. Ironically I have noticed that European designs almost always have the resistors and always on the high side. Check out the schematics of Leak power amplifiers, for example.   
      The same goes for different methods of providing cathode bias for multiple output tubes, including push-pull with 2 tubes or push-pull parallel with 4 or 6 tubes like in the older bi-amp Magnavox consoles. The biasing is a completely separate problem than oscillation suppression although certain tubes such as EL84 have both problems worse than say, 6V6G. Let me go over oscillation suppression first because the results can be so disaster prone and hard to even verify that you have them in the first place.
       I'm going to do short posts because this computer times out and I don't want to lost 25 minutes of typing !!
     
     
       
     
     
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 20, 2018, 08:52:53 AM
     Output circuits LEAST likely to oscillate are.....
                    single ended low mu triodes (high capacitance plate to control grid) with
                    bakelite (RF lossy) bases, 
                    bulb shaped glass envelopes (long internal leads compared to GT bulbs),
                    unbypassed carbon resistors in the cathode for bias (no inductance compared to wirewound)  and
                    control grids driven by a cathode follower (high damping even at RF frequencies ).
     Everything is against you, at least if you're designing an oscillator circuit. Push pull beam power tubes are more prone to  oscillate because the control grids are more isolated from the plates capacitances thanks to the screen grids and you have twice the transconductance of one tube and yet the capacitance is still one tubes amount because the wiring inductance separates the two tubes from each other, at least at high RF frequencies.
       
                The MOST likely to oscillate circuits would be
                             push pull parallel tubes, including both channels if they have common cathode and screen leads (like the 9300 amp) with
                             high transconductance tubes (like EL84) with
                             glass bases (low RF losses)   
                             short direct internal tube leads,
                             wirewound cathode bias resistors (inductive),
                             compact physically small tubes (EL84, as compared to biggies like 6CA7)
                             12AX7 driver tubes (high impedance) 
                             high line voltage (higher than in the fifties, maybe 125 VAC)
                              low loss mica tube bases (needed for hot tube temperatures)

time to post
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 20, 2018, 09:29:23 AM
         So you can see that the 9300 amp with 4 EL84s, a common wirewound cathode resistor, and no isolating control grid or screen grid series resistors, a 12AX7 driver tube and electrolytic bypasses for screen grids and cathodes (at VHF frequencies they are probably inductive due to lead lengths if nothing else) and a higher than designed for AC line voltage is almost certainly singing away at some VHF frequency, if not constantly, then during current peaks when driven with large audio voltages. The old push pull parallel power amps in the old bi-amped Magnavox chassis had RF chokes in the plate leads and 120 resistors (I think) in the control grids but nothing in the screen grids.
         My personal gut feeling is that 4,700 ohm resistors in series with each control grid, placed right at the socket, and 470 ohm resistors in series with each screen grid, again, placed right at the tube socket, will make oscillations impossible no matter how high the transconductance is of any EL84 and no matter how unfortunate the wiring and component placement is.
           Incidentally, one way to check for the parasitic oscillations is to take a small old black and white TV and set it to an unused channel with snow and connect a short wire to the 300 ohm antenna terminal that is placed close to the amplifier chassis. You will see something on the set besides snow when the amp is turned on and off, maybe wavy lines or the snow will blank out to a white screen. 
           I've got to go get an echocardiogram test soon, if they- let me leave in one piece, I wil post more later about the cathode bias resistor and bypass caps for individual cathodes
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 20, 2018, 11:17:09 AM
The 8800 and the 9300 series Magnavox amplifier chassis both use 6EU7's as drivers.  Allegedly a low-noise twin triode version of the 12AX7.  I have found them problematic, particularly with short, most commonly heater to cathode shorts.  I have considered converting over to the 12AX7, but, according to your text, that might cause more trouble than it would alleviate.

A tidbit of trivia that I learned recently.  Magnavox used particle board in the bottom of some of their cabinets for a reason, other than just being cheap.  It was used to prevent the cabinet from "drumming".  Replacing particle board with plywood would negate this desirable effect.  So, if particle board is flaking off, most likely due to the fact that it was not designed to last nearly 60 years, and due to the fact that the glue deteriorates and lets it fall apart, I was advised to stabilize what is there if it is still structurally sound.  Using shellac or epoxy was the recommended method.  If the particle board is of unsound condition, I was advised to replace it with MDF.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 21, 2018, 02:33:10 AM
         I see on the under-chassis view of the 9300 power amp your missing 100 ohm 5 watt resistor. One lead is soldered to the wiper of R2 the hum balance pot. That resistor is nowhere near the EL84 cathodes or C1 the metal can electrolytic cathode bypass cap mounted above the chassis but...…it is right next to the 5U4 rectifier socket.
          Now suppose something went wrong with the original resistor and it smoked and that smoke went all over the rectifier socket. With 600 volts AC between across  socket pins and 330 volts DC on another pin and maybe other voltages on other pins if they used them as tie points for maybe 120 volts AC, a bunch of burning carbon smoke all over those pins would start a big flaming arcing mess which would take out the socket and maybe the power transformer.  After replacing all that, maybe the technician forgot all about the original resistor. Or is it there tucked somewhere under the wires and you were looking at the EL84 sockets or C1 the bypass cap ??  Hope it pops up after all.
           I looked on google at regulated power supply schematics of Kepco and Lambda. Both companies along with Power Designs and good old Hewlett-Packard, made lots of variable DC regulated supplies with 6 or 8 or even more pass tubes in parallel, tubes like 5881, 6L6GC, 6W6, and even 6550s. They all, without an exception, used parasitic suppressor resistors of between 100 ohms and 47,000 ohms at each control grid and between 100 ohms ad 680 ohms at each screen grid. Some even had 33 or 47 ohms at each plate. Just mentioning that to show that EL84s deserve the same precaution because of the common cathode and screen grid leads going from socket to socket. They may as well be all in parallel in a common circuit at high enough frequencies even though they are really in two different channels and push pull circuits. Magnavox did use them In many other parallel circuits, they must have assumed it wasn't necessary in this layout.

            I'm going to post this now before this computer clocks out Good luck with the case of the missing resistor.   
             
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 21, 2018, 07:40:18 AM
I had the amp on the bench for a time yesterday.  I have not found ANY 100 ohm, 5 watt resistor anywhere.  This begs the question:  Do I have any output transformers left?  The instrument is alleged to have a "bad hum."  If it hums, it works.  And how much did those Radio Shack output tubes go thru with no bias on the cathodes? 

BTW, your scenario about the cathode bias resistor smoking and taking out the rectifier socket is eerily reminiscent of exactly what happened in my Imperial. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 21, 2018, 09:47:09 AM
      Hopefully without any resistor the 4 EL84s loaded the power supply so much that the DC voltage wasn't nearly as high as it would be with the normal current draw. The screen grids were fed from a dropping resistor so that would be a lower voltage since power pentodes like EL84 and EL34 have  greater screen grid current draw than beam power tubes like 6V6 and 6L6.  The filter choke resistance and 5U4 resistance would also lower the voltage with higher DC currents so you might have dodged the bullet.
     more later, im out of computer time again !!
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 21, 2018, 03:40:45 PM
     Some loose ends. Looked at a bunch of EL84 power amp circuits from Amperex and Mullard manuals. They all had separate cathode resistors and separate bypass caps. If the resistor was less than 300 ohms or so the bypass cap was 100 uF, if greater than 300 ohms, 50 uF and if greater than 500 or so ohms, 25 uF. almost without exception. These were all hi-fi amps with response down to 20 Hz flat,  (with the negative feedback as part of the circuit).
      As far as I can tell, you should have the same cathode voltage, Ohm's law wise, by adjusting the cathode resistor up in value the same ratio as the current through it goes down in value. If the total cathode current was 120 milliamps, each individual EL84 should be one fourth of that or 30 milliamps. Then each tube's resistor should be 4 times 100 ohms or 400 ohms. You don't need wirewound resistors, just 2 watt carbon resistors should do. Bypassing each resistor with its own 50 uF capacitor and there you go.
        The various tube manuals give 1 Megohm as the maximum grid resistance so you are safe leaving the values what they are now, 680 kohm in the upper grid and 220 k in the lower grids. The 1 Meg value surprised me but all the manuals including Sylvania and GE had that value, and they all had 300 kohm for fixed bias operation.  I looked up 6V6 and 6L6 and they were 100 kohm fixed bias and 500 kohm for cathode bias. So I assumed the same for 6BQ5 but it wasn't so.
          I am just about 100 % certain the 9300 amp will sound as sweet and pure as ever you heard it with 4 series grid resistors of 4700 ohms or so, 4 screen grid resistors of 470 ohms or so, 4 individual cathode resistors of 390 ohms or so and 4 individual electrolytic bypass caps of 50 uF or so.  It may look a little busy around the tube sockets, but look at the bright side. You will be able to measure each tubes individual current both total and screen by reading the cathode resistor voltage or screen resistor voltage. You can check for leaky coupling caps to the control grids by grounding the grid and checking for any change in the cathode voltage.
         I know the feeling of cutting into the circuit, but Magnavox did the same changes in their push-pull parallel 6V6 or 6L6 big bruiser amps.   
       
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 21, 2018, 04:18:08 PM
        Some more odds and ends:
           Found a circuit labelled Mullard circuit "modified for the United States". The only changes were the tube names, 6BQ5 for EL84, etc, and the only other change was..…. eliminating the individual output tube cathode resistors and and using one common resistor and cap for both cathodes !!   
       Clearly a case of "Not Invented Here" !!      " Mebbe I gotta use thim gol-dern furren tubes, but I shur aint usin thim  gol-dern furren cir-kits too  !!!" 
        The RCA tube manual would refer to the Armstrong FM discriminator as the "Foster-Seeley" discriminator rather than admit that Edwin Armstrong had anything to do with FM radio.
        The Magnavox 6L6 and 6V6 push-pull parallel circuits were strange. They would put a plate RF choke in 2 of the three 6V6 tubes but not in the third one. Same for the 120 ohm grid resistor. Two out of three. Maybe they didn't bother with the tube closest to the transformer lead ?
        Also... saw a common oscillator circuit for FM tuners that consisted of a bypassed-for-RF plate lead, a tuned circuit for the grid lead and an inductance for the cathode lead. The cathode inductor was the only part needed to make an amplifier circuit into an oscillator, at least at 100 MHz FM frequencies. A good argument against using low-ohm-value wire-wound resistors for cathode bias audio output tubes, especially if you have no oscillation-suppression parts in the grid circuits.
       
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on July 21, 2018, 05:23:27 PM
       
        The RCA tube manual would refer to the Armstrong FM discriminator as the "Foster-Seeley" discriminator rather than admit that Edwin Armstrong had anything to do with FM radio.

        The Magnavox 6L6 and 6V6 push-pull parallel circuits were strange. They would put a plate RF choke in 2 of the three 6V6 tubes but not in the third one. Same for the 120 ohm grid resistor. Two out of three. Maybe they didn't bother with the tube closest to the transformer lead ?

Several of my Zenith table radios have stickers on the back touting their Foster-Seeley discriminator.

And I've always wondered why the Magnavox amps had those chokes in the output plate circuits.  Guess it was for oscillation suppression?

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 21, 2018, 10:35:03 PM
 I assume so. I've seen plate chokes in McIntosh power amps with 6550s. But the control grid and screen grid are supposed to be the ones that suppressor resistors have the most effect. Sometimes a regulated power supply with a ton of  5881s in parallel will have 22 ohm plate resistors in addition to screen and control grid resistors but not often.  Also you may see low value resistors in series with each cathode but that is more to equalize the current among wildly differing tubes. In that kind of equipment, if one tube goes bad you're supposed to be to replace it with whatever's in stock without matching it to the others.

     I wish they put plate chokes in every tubes plate and grid resistors in every tubes grid.  Someone's pay raise must've been tied inversely to parts count.
 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 22, 2018, 03:26:08 AM
      Seeing a row of high transconductance power tubes like 5881 all in a row with grids, cathodes and other elements in parallel and with no suppressor resistors anywhere, I feel like I'm looking at a lot of bolts in a row holding a metal cover onto a highly stressed vibrating car engine but with no Loctite, flat washers or lockwashers.
      Seeing a similar row of those same bolts but with Loctite on the threads, flat washers and lockwashers under each bolt, and the steel wire that ties bolt to bolt through holes in the bolt hex pattern, like on some jet engine, that's like seeing all those resistors coming from the screen grids and control grids. In the former case you hope the bolts are all tight and won't get loose, in the latter case, you know for certain that those bolts aren't going to get loose.
      There is one more wiring change I have done on some units with strange ground layouts, like the Dynaco MkIII power amp with KT88s. That is to disconnect the center tap of the power transformer plate winding  from the ground lug, and adding length to the wire, I thread it along the red high voltage leads, to the rectifier socket, then along the red DC lead from the rectifier socket to the filter capacitor, and solder it to that filter capacitors ground lug. The same with the power transformers primary circuit. The wire follows the other black wire to the power switch, the fuse holder etc. That way, the charging pulses to the first filter cap flow through equal and opposite currents and don't induce  hum or buzz into the circuit wiring. It cleans up the last vestige of hum and buzz from the loudspeakers 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 22, 2018, 10:36:13 AM
 That's interesting Chris, I had some Zenith tube AM-FM table radios and I never studies the various stickers on their back covers or underneath.
           As far as I know the RCA "Radiotron Designers" manual both the early thin black cover version and the super thick red covered later version was the only place you would see the FM discriminator called the Foster-Seeley discriminator. The other FM tuners would call their circuits "genuine Armstrong dual limiters and dual diode phase discriminator" to assure people it wasn't the more economical one tube regenerative detectors or the "Fremodyne" circuit which didn't provide as good a rejection of AM and static.  I think some of the alternate circuits were a way around Armstrong's patents more than to use one tube rather than three.
            Poor Edwin Armstrong, as my mother used to exclaim about anyone deserving sympathy.  He got cheated out of his regenerative detector  and maybe his super-heterodyne circuit by Lee DeForest and the entire FM radio system by RCA's David Sarnoff. I think the superregenerative detector was the only invention that he didn't lose the patent on. I always hate to see people get away  with something everyone know they didn't earn  just because they know the other fellow can't afford lawyers but they can.
         
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 22, 2018, 11:13:12 AM
Here is the latest picture of the badly hacked amplifier.  I still don't see a cathode bias resistor.

The rectifier listing to starboard.

Lots of nicotine everywhere.

Looking a little better.  Lacquer thinner and PB Blaster to the rescue.

An extra resistor where it's not supposed to be.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 22, 2018, 11:29:12 AM
I have no sympathy necessarily for Edwin Armstrong.  When he attempted to deal with Sarnoff and RCA, he came to a gunfight with a slingshot.....
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 22, 2018, 01:40:09 PM
In deference to the "poor Edwin" point of view.....

There is no question about the fact that David Sarnoff promoted RCA and protected its interests like a junk yard dog.  He was arguably one of the most ruthless businessmen ever in this country.  Perhaps the only individual who dealt with Sarnoff successfully was Charles "Boss" Kettering from General Motors.  Those who criticize David Sarnoff for the way he treated Edwin Armstrong may find karma in the fact that David Sarnoff's hand-picked successor, his son Robert, was largely responsible for sending RCA into a death spiral from which it never recovered.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 22, 2018, 01:47:48 PM
       That light green wire-wound resistor where it's not supposed to be seems to be the missing cathode resistor.  If I am seeing right, anyway.

          One end goes to the slider of the hum balance pot and the yellow (cathode) wires that daisy chain to the EL84s and the other end goes to a ground lug. The resistor is physically an inch or two from the one pictured in the 9300 amp download but the leads seem to go to the right wires of the circuit, all with yellow cathode wire code. Take an ohmmeter to the yellow cathode leads at one of the EL84 tube sockets and see if you don't get 100 ohms from it to ground.

           Let me post this before it times out on me and then I am going to stare more closely at the different pictures.   
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 22, 2018, 01:56:56 PM
   Both David Sarnoff and Edwin Armstrong look like a couple of tough hombres, though I realize that in that era of bigger-than-life shakers and movers they usually had a frowning scowl on their mug to intimidate the casual viewer. Not everyone stuck their tongue way out for the camera like Albert Einstein. I'm sure they both dealt with each other in a "mutual collaboration in mulishness" as Rex Stout had Nero Wolfe saying to Archie Goodwin after one of their spats. As they say, it's a jungle out there and the weak go the wall.
     Out of time again. !!
     
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 22, 2018, 02:28:28 PM
  OK !!  Now I am staring back and forth at two printouts, one of your closeup of the light green resistor and the other page 8 of Photofact 586 of the downloads.
         The two parts are at right angles to each other and one has the hot ungrounded side going to the hum balance pot while the other has it going to the yellow cathode lead of the end EL84 socket. That white wire looks unoriginal (Teflon ?)but it seems to make the connection to the 2 different locations of the ungrounded lead. I see the other yellow wire going from the hum balance pot slider to a lug on the big electrolytic can, probably  to C1D the 20 uF at 50 volt lug.
        The wires emerging from the replacement transformer look pretty gruesome and it looks like they are using the rectifier socket as a tie point for the center tap of the 600 volt secondary. The filter choke wires look like they are spiraled around aimlessly instead of a twisted pair which won't help the hum problem. It may be that the new location for the wirewound resistor could be wrong for inducing hum although it is carrying DC and not filament current so I guess it's OK.
   out of time again !!
       
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 22, 2018, 02:59:12 PM
             Is it me or did someone try to redo all the grounds in this chassis ?  I see a lot of thin white wires between the RCA input jacks, the balance pot near the 6EU7s, and some other spots here and there----including the ungrounded cathode leads of the cathode bias resistor. The power transformer looks undersized compared to the original, at least the mounting lugs look like they are inboard from the original. the Photofact picture looks like all grounds were directly soldered to the nearest chassis metal, not bus-barred with separate pieces of white wire.
             You take pretty clear pictures. Do you use a tripod ?

       I've been googling such images as "KT88 audio amp circuits"  because now I am really curious if all  these amplifiers use control grid and screen grid suppressor resistors like I've been claiming and the variation in resistances, when they do use the resistors at all, is amazing. From 47 ohms to 10,000 for control grids and 22 ohms to 1000 ohms for screen grids. I give up, I guess the whole world of designers threw the towel in on this one. The older manufacturers like RCA and Zenith and Magnavox  tended to not use any because after all you certainly didn't need them with 6V6 bottles with a low impedance driver tube like 6J5. In their more powerful units with push pull parallel 6L6s though they did do the occasional grid resistor here and  there so there must have been an audible sound difference and on a regular basis, not just one out of every 1000 units.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 22, 2018, 03:40:24 PM
I changed the rectifier socket.  When I removed the ONE screw holding it in, the ear broke off.  Probably a Radio Shack socket..... ;)

The resistor we saw is, indeed, there as a cathode bias resistor.  I don't know what it's rated value is, but is measures 80 ohms, this verified by three VTVM's that I had hot on the bench.  It is grounded directly to the center tap of the power transformer.  The little yellow wire you mention, from the center tap of the hum control goes to the cathode bypass cap in the filter cap can, section "D" if memory serves.  It seems redundant to me.  It appears factory.  There is an orange wire running from section "B" of the filter caps to the 6BQ5's.  It has a bare spot in it for whatever reason.  I saw the wires from the choke.  I'll unsolder those and clean that all up.  The wires from the Molex connector to the primary of the power transformer are taped together.  He did use good, sticky tape, though.   ;)

The 220K grid resistors are 20% tolerance.  Five of them measure 150K-170K, and the sixth measures 200K.  176,400 is the minimum at 20%.  I have not run across grid resistors that measure low.  Usually I find them drifted high.  I'll replace all six for good measure.  The 5600's checked okay, as did the 2200's.  I'll replace the two paper coupling caps and restuff the filter cap can.  We should be good to go, amplifier wise. And I'll replace the cathode bias resistor and the bypass cap.  I want to put this all back like the schematic says to establish a baseline of performance.  We'll take it from there.

The jury is out on the power transformer.  I measured resistances and found them all acceptable.  I don't see any reason the power transformer should not be okay.  It may be undersized, which we can tell with voltage measurements when the system is under power.  It may have to be replaced.  If that is the case, I'll get one at AES this winter when I'm out there and won't have to pay shipping on a heavy transformer.  It looks a tad smaller than I'd think was normal, but apparently it worked for some time.  We'll see.....

I do not use a tripod.  I appreciate your kind comments.  I have a little cheap Walmart Nikon digital that I have had for ever.  I have trouble with it not wanting to focus when using it inside.  If I have lots of light on the subject it does better.  I took those pictures on my electronics bench and there was LOTS of light.  I don't like using the flash, as it makes the pictures too bleached out.  I don't have something set right, but I have no idea WHAT. 

As it is wired now, with the cathode bypass cap in the filter cap can, the yellow wire to the hum control is necessary.  When I replace the cathode bypass cap and put it down by the cathode bias resistor, the yellow wires gets cut out.  We no longer need it.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 22, 2018, 04:05:03 PM
I now have 48 1/2 hours in this project.  I'm not even started yet.  I'm cleaning up somebody else's mess so I can make my own.  I almost have all the wiring cleaned and have almost figured out where it goes.  The external speaker switch is hidden in front of the TV tuner.  That is gonna be fun. 

Magnavox removed all the paper caps in the Multiplex adapter.  These are all ceramics.  All there is to do is to replace the 30Uf filter cap and test the Radio Shack tubes to make sure they are all good.  Why would they not be?  I have found four original Magnavox branded tubes in this instrument out of the 36 present. 

I used 320 grit paper, 0000 steel wool, PB Blaster and lacquer thinner to clean the MPX adapter.  It is better, but it's not done yet.  I also found a way to make tube shields look nice without painting them.  I was proud of myself.  Quite by accident, really.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 22, 2018, 05:23:35 PM
    That MPX chassis is certainly shiny without looking like brushed chrome. You must have that touch with the cloth. And a steady hand If not using a tripod.
     Well you're recapping anyway, but I will still mention that if you measure 80 ohms across that cathode resistor and it is actually 100 ohms like the original part, maybe the 25 uF part of the 4 section electrolytic is very leaky if not almost a short at the 12 volts DC it would have on it during power up. That might explain some of the overheating or hum. It's a shame the original guy fixing this chassis didn't make a few measurements before all the  re-grounding etc. My general experience with resistors changing value is that high value resistors of low wattage but with DC on them seem to go higher with age. The power dissipated may be well under the wattage rating but it seems the high DC voltage somehow eats out the small amounts of carbon that is very diluted by the insulating binder which makes up such a large percentage of the mix in a high ohm small wattage resistor.  A magic eye tube with say an 820,000 1/4 watt resistor (going right to the highest DC voltage and installed at the socket where you forget there's a resistor), usually is nearly open. 470,000 plate load resistors are often above a megohm while the same resistor  in the grid circuit with no DC is OK.
          I'm sure you have a line fuse as part of the restoration, despite it not being original, after what has happened to this particular unit !!
          Out of time again !! 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 22, 2018, 10:54:45 PM
 Is the center tap of the HV secondary and the cathode resistor going to a ground lug of some sort or just to each other ? That means the filter cap charging pulse current is flowing through the c0hassis metal to the fiter can at the other end of the chassis. Possible hum source
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 22, 2018, 11:23:28 PM
    I only mention the power transformer not fitting in the original mounting holes because it indicates the repair person wasn't able to gat an original replacement part from Magnavox but had to order the nearest substitute that would fit from a Lafayette type catalog. Makes one wonder how old the unit was when the trouble started.
     I totally agree about your wanting to get it working as an original unmodified unit. At least you will a good reference point. Little changes like slightly lower 60's era line voltage or adding a line fuse can always be contained in an external plug in metal box next to the wall outlet. That's about the only difference about the 2018 operating conditions. Plus an extremely crowded FM band.

      Is your pilot light mounted onto a metal bracket of the TV chassis or otherwise touching ground ? It looks like  Magnavox has the filament winding floating from ground and connected to the + 12 Volts DC cathode bias. Grounding the pilot lamp mounting bracket would partially short out some of that 12 volts DC through the hum balance pot. I assume you get 80 ohms without the pilot lamp terminals connected. Who knows what else the repair man reconnected different than the original, even including the pilot lamp mounting.
 
       You have about 40 more hours into that unit over and above what I could get done in a year. I'm hoping to really- pour myself into things this autumn and winter. I just
 have to get my aunts console with it's own 9300 amp to my house before she starts getting antsy and calling -young guys to take away this or that bulky items. Her memory is no longer as good as it was. I'm pretty sure its turntable says feather touch on it. Its an ivory white provincial cabinet and I have no idea as to he quality of the base wood. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 22, 2018, 11:41:00 PM
The pilot light is (or was, until I futzed with it and got it off its trolley) situated under the CRT, in the middle of the cabinet, mounted in the wood cabinet.  The leads from same are duly twisted to prevent hum from that source.  I'm going to install a fuse in the amp chassis as soon as I get some service literature and figure out how big a fuse I need.  I put one amp fuses in the amps of my Concert Grand with their 12 tubes in each amp.  This power supply will be powering 19 tubes, as the TV has its own power transformer and rectifier system.  Total power consumption of the instrument, listed on the model identification sticker is 455 watts.  I figure about 160 of that for the stereo and the rest for the TV chassis.  Would one amp be about right?  There is a circuit breaker for the TV.  This is just a guess until I get service literature.  I have a friend looking it up for me.  We'll have to wait and see what he can come up with.

The center tap of the power transformer is connected to a ground lug on the chassis.  Apparently, somebody was hunting a hum and grounded the cathode bias resistor directly to the center tap of the PT.  They are not floating, they are attached to the ground lug on the chassis.  The white wires you see are factory, I believe.  I have seen those before.  I never have figured out their purpose.  You say redundant ground? 

I believe I have a handle on the hack work.  The most critical thing that was done was to leave the old filter caps in.  It may have been done 30 years ago, and the caps tested okay then, and may have served for several years.  Only in retirement did the filter caps become leaky.  And someone connected the negative lead of one channel to the hot lead of the other channel's speakers.  That was not good.  And the cheap rectifier socket and all the Radio Shack tubes.  Nasty soldering and leaving wires all over the place.

Here is a picture of the power wire from the tuner to the changer.  It was wrapped around speaker wires.  All the Rat Shack tubes, with the exception of some 6EU7's, are going bye-bye, right into File 13, good or no.   ;)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 23, 2018, 04:29:07 AM
       I have been magnifying your excellent photography of the under chassis shots with a magnify function I didn't know this computer had and now I am really curious about something. As far as you know personally, has this chassis been successfully powered up since person X replaced the power transformer ?    Not counting what anyone has told you about it.  Or is the most anyone has gotten out of was a hum and little else?
         I am asking because unless the transformer has its own different wiring color code, I think they may have gotten some of the connections wrong, at least for the filaments. Maybe use your ohmmeter to verify some of the winding resistances and also verify that windings that should be floating with respect to each other such as the isolated filament winding going only to the Molex connector, the AC primary winding are truly floating from each other and chassis ground.   The main filament winding should have 267 or 287  ohms or so from  either lead to chassis ground if the hum balancing pot adjustment is centered.  (750 ohm pot divided by 2 is 375 ohm, which paralleled with another 375 is 187 which added to 100 ohm cathode resistor is 287 or if 80 ohm resistor 267 ohms from the filament winding to ground. ) Maybe, usually I goof something up in these calculations.
       Anyway, if all these isolated windings really measure isolated from each other, maybe yank out all the tubes and power up the chassis on a Variac and use a Simpson or a floating battery operated DVM on the AC HV scale (don't use a VTVM if it connects to the AC line for power) to see if the EL84 filament pins 4 and 5 really have 6.3 Volts AC on them, and also the isolated 6.3 Volts AC to the Molex connector. See if you have 300 Volts AC to ground on either of the HV AC rectifier plate connections and 600 Volts AC plate to plate if your floating DMM goes that high.
      Something about the color coding of the wiring just seems wrong judging by the views I see around the filament wiring. I know that some power transformers "polarize" their winding color coding by having one end of a winding a solid color and the other end the same color but striped and your transformer may be one of those. If so, I apologize for being an alarmist and maybe you have heard this amplifier for yourself and it has normal sounnd,, just with some added hum, but it never hurts to make a few measurements wihout any tubes in their sockets if you haven't personally heard it.
      Out of time again !!
       
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 23, 2018, 06:27:43 AM
   Oops. divided by 2 twice which I think was an error. should be 375 plus 80 or 100 depending on the mystery resistor. so 475 ohms to ground or 455 ohms to ground for the EL84 filament leads on pins 4 or 5 of the 9 pin socket.
    I see two leads that are the same color green solid from the transformer and one that is green with a yellow stripe. Normally it would be 6.3 Volts AC green to green with the green/yellow stripe being a center tap. It looks like the green and green/yellow stripe go to pins 4 and 5 on the tube socket while the other solid green goes to the terminal which then goes to the Molex connector. Something doesn't seem right about that.
         At least they left everything else, the caps for example, alone for you to tend to instead of doing their own version of a recap job which you would have probably had to do over anyway.
        I wish I had my aunts 9300 upside down and in front of me to look at. I don't think they ever had to service theirs so it would be pretty original and probably extremely dusty.    57 years worth at least
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 23, 2018, 01:15:37 PM
I have never plugged this thing into power, personally.  The seller told me it had a "bad hum" and so he shut it off and sold it to me.  He felt the project was above his abilities, but he wanted to see the ST restored and not trashed for parts.  This is all I know about it.

Power transformers are not one of my favorite things to mess with.  I guess so many wires intimidate me a little.  I need to get complete service documentation for the instrument so I can find out the different values I'm supposed to have.  I'll admit that what you just posted flew right over the top of me.  I'll read it again, slowly, and see if I can glean what you were offering.  The work does not look recent to me.  I don't know how long Nick had it, but I know at least from October of last year to June of this year.  I don't know where he got it.  You know just about as much about this project as I do.

It is my understanding that power transformers have a universal color coding for the wires.  I've seen that code somewhere, probably have it somewhere, but the exact WHERE escapes me.  Maybe that should be one of our avenues of investigation.  Correct wiring on the PT is not something I even considered.  I was assuming the instrument had run for some time since the work was done.

Could you explain what you mean by "floating VMM" and "floating to ground"?  Can you tell me how to identify the different taps out of the power transformer, i.e. primary, 6.3 volt filaments, 5 volt filament. like that.  My thought was to repair the chassis, change caps and that, then power up on the Variac and dim bulb without the rectifier.  That being okay, then put the rectifier in and bring up B+.  Maybe my investigation should start with filament voltages and go up from there.  What a mess.  "Gloriously Complicated."

And, for what it's worth, the rectifier checks good.  All the tubes in the amp I have checked are good.  If something in the PT was miswired, would not that have potentially damaged tube filaments?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 23, 2018, 02:32:51 PM
Referring to the schematic ( which I should probably post so everybody can follow along) you will notice that the filament wires to which you refer are actually correct as the picture shows.  One filament wire is green, the other green with a yellow tracer.  So that is correct.  As to the wire going to the Molex connector, there are actually two pairs.  One pair, X1 & X2 on the drawing go to the filaments.  In the picture, these two wires, one purple, one green, come off the 6EU7 filament nearest to the Molex connector, pins 1 and 2.  The purple wire runs to the Molex connector, the green wire kinda wraps around the hum control on its way to the Molex connector, also correct.  Wires marked Y1 & Y2, coded brown and brown with a yellow tracer, going to the Molex connector, are also correct.  These are the two wires with black tape on them in the picture.  They provide B+ to the tuner chassis. Two red wires go to the rectifier plate and two yellow wires (faded to tan) go to the cathode of the rectifier, also correct.  The center tap is red with a yellow tracer, correct.  I believe at this point the PT is wired right, according to the schematic.  If we have voltages like they should be and the transformer does not overheat in service, we should be golden.  Your suggestion of checking the PT wiring was an excellent one.  Faded wires coupled with photography can be confusing at times.  Troubleshooting things you can't lay hands on is not easy, either.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 23, 2018, 02:40:47 PM
The traditional Magnavox wiring legend, typically pasted to the cabinet back or on the floor of the cabinet is pasted partially on a speaker board and partially on a panel for the front in this cabinet.  The drawing is really fragile and brittle.  No way can I remove it in one piece.  My thinking is to cut the diagram in two so the speaker cloth can be removed.  I'll cover the diagram in clean shipping tape and leave it alone. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 23, 2018, 02:52:02 PM
    Floating DMM means you are not using an AC powered  vacuum tube voltmeter with a line cord and plug. You need a battery operated digital multimeter like a Fluke or a multimeter like a simpson 260. There is no connection to AC line and you can measure voltage   on a powered up transformer with worrying about which lead is going to what. The transformer winding is floating, meaning no connection to chassis ground, and the meter connection shouldn't be grounded either especially measuring the 600 volt winding to the rectifier plates.
            I am going to jot things down and write in in an unhurried leisurely way to make sure what I write makes sense. Then I plan to log on and type it in in my 30 minute window this dumb computer rations out so it may be a few hours til the next post.  When I write stuff without several rereads, it tends to read horrible.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 23, 2018, 05:01:19 PM
   It just occurred to me that the transformer case might have a part number stamped into one of the metal shells. Maybe a 6 or 7 digit number if not something with a P in front of numbers, P for power transformer rather than A for audio. If its a Stancor, UTC or Triad there are catalogs on line and the color code would be part of the information for each individual part number
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: voxACthirtee on July 23, 2018, 09:07:22 PM
Not to be a dick, but i've seen the chassis pic and i think you guys are really, REALLY overthinking this.
It took me about 2 seconds to identify the cathode resistor, without magnifying anything.This amp looks like the 20+ other maggies i've been through.
They built and wired these, back then, in a FAR from anal way. Wires strewn about,grounds here and there.Sometimes it goes against conventional wisdom of the "ground planes" and twisted wires we would build on today,but they worked and were quiet when the caps and tubes were good.
I've been through plenty of the Maggie high end biamps and they are wired just as haphazardly.
Change the caps, clean up some of the wiring as you go, and i'd bet a dollar you'll be just fine.
Use a new set of MATCHED power tubes, or if you have old tubes, use a good tube tester that matches output to find a good set. Even better if you have a tester that tests for amperage draw. Don't just use old tubes that test "good" on a meter. They match tubes for a reason.
Also, as this would be the last of the Maggie tube amps, while it certainly could be a replacement transformer, it could also be that they were basically using what they had left. There are plenty of stories of tube manufacturers who in their waning days slapped the last of their product together using whatever parts were left.


Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 23, 2018, 10:51:00 PM
               That is so true as far as looking for a complicated explanation of a simple problem. I do it all the time especially when trying to solve a car problem.

            Case in point.....I saw how that replacement power transformer was chiseled to make it fit where the old transformer went and jumped to the conclusion that the guy could also eaasily got all the leads connected wrong. But I just looked at the schematic of the concert grand or one of those with several power transformers. One of them had the color coding I was used to. 2 solid blacks AC primary. 2 solid greens filaments. 2 browns another filament winding. 2 solid yellow  5U4 filament. 2 solid red  HV winding  red and yellow stripe center tap HV winding.  so far so good
              But------the OTHER transformer was the same at least for HV winding and for 5U4 filament   however the other windings went as follows ..…...black and black/ red stripe  AC primary    green and green/yellow stipe  filament  brown  and brown/yellow stripe  other filament. This is what the replacement transformer is showing in electra's 9300 amplifier. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 23, 2018, 11:04:09 PM
I am having a ball with this thing.  We have had fun bantering information and questions back and forth.  I reckon we have gotten a tad long-winded, but what's the harm?  I believe at this point that some caps, resistors, maybe a quad of output tubes and cleaning up some wiring we'll probably be okay.  I need to be sure is all.  You see what they want for an old 9300 series amp on the 'bay?  I need to make sure I get this one going.   ;)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 24, 2018, 01:37:43 AM
           Well put !!    Sometimes the ex-cigarette smokers are the ones who go around grabbing lit cigarettes out of the hands of strangers with tales of impending doom. Such was I, such was I !!  However.........…….Let me tell a fictional story but which is based on multiple actual experiences rolled into one.
           A reliable vacuum tube power amplifier circuit is "improved" because of a superior new tube that has already been adopted by many competitors. Initial trials indicate that the same chassis and circuit work fine and an initial run of 200 units is planned for the new tube in the same old circuit and chassis layout. Everyone is happy, the designer, the test technicians, the financial people who see only positive numbers in all the column, minimum redesign and rework etc. After that another run of 500 u=nits is started, increased labor is needed, new-hires for assembly  and electronic testing.
           Suddenly problems. one out of every two units don't measure at all well. Either they are very good or very poor with nothing in between. Finally an engineer looks things over. He issues instructions to push these leads close to the chassis,, pull the other leads as far up as possible, orient this part at right angles to that wire. Things are fine again, the few units that still act up are fixed by selecting the best tube in the socket closest to the preamp tube and the weakest tube furthest away. Pressure is put on the engineer by the technicians to issue a service bulletin with the modification instructions, but somehow the hand written notes are all that is done. No one issues anything officially. Finally, after field reports flood in, a service bulletin is issued...…….to bend the leads this way and that, put the weakest tube in that socket. When a new run is started for 500 units is started, several resistors are added which eliminates the problem.
         I have seen this same story for placing the oldest dat code chips for this location and the newest for that. In milspec stuff no less !!
 
       
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 24, 2018, 02:08:11 AM
              I am having a lot of fun too and am learning more than I care to admit !!  Especially as I was thinking the information flow was one way and in the other direction.
In the end, gut feeling and experience will prevail but it never hurts to have several plan Bs on hold just in case.
             If everything powers up fine and sounds as good as they all should, you are in the clear. If you want a safety factor, you can always-s adjust the variac up above the line voltage a bit and monitor the voltage across the cathode resistor to see that it increases steadily with increasing AC voltage with no sudden jumps in current.
              If it still has a hum that is above what you would expect and you have eliminated all the usual causes, then it might be time to look into the plan B type of causes, parasitic oscillations and things, but even checking for them doesn't have to be hit or miss, since you will know what to look for and simple tests  will always verify what is going in in the circuit, tests that were evolved with the problem in mind.
            But until the problem surfaces, look for the bad solder joints first. I recently was trying to check for leaky fuel injectors and was pouring can after can of injector cleaner into the tank when one dark particularly humid night I raised the hood with the idle loping  and saw in the darkness a  weak spark jumping from one of the plug wires to nearby metal.   
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 24, 2018, 10:06:11 AM
Another thing to consider is this.  We don't have any idea who is actually following along with our little project.  What newbie may be lurking.  They may have gotten something "old" and would like to see it working again.  They may have little to no experience with this type of thing.  They may be hesitant to ask questions, lest they are made to feel foolish.  They read about a bunch of guys with 40 years experience apiece fumbling and fetching their way thru an amp chassis and feel emboldened to try it on their own project.  We all live and learn in this hobby together.  We learn from each other.  That is the fun in it for me.  That is what this forum was started for------the care and feeding of console stereos.  I admit that I already have ten times the money in this thing it will ever be worth.  After I do an "every nut, bolt, screw, wire and connection" restoration on this thing, have it in perfect operating condition, redo the cabinet, the whole shot, better than new, then I croak suddenly, my wife would be very fortunate to get $100 out of this thing.  That is not the point.  The point is that a total stranger promised to hold this thing all winter, strictly on my word, a total stranger to him.  My promise to him for his kind consideration was that I would restore this old abandoned Stereo Theater to the best of my ability.  That's what I intend to do.  Bill is a big a duck in this puddle as I am.  Without his valued friendship, this would not be happening.  I waited three years for this.  I intend to take it slow, enjoy every second and savor the moment like fine wine.  And have THE nicest Stereo Theater on the planet.  So, if you are in a hurry, pardon my getting in your road.   ;)

Ed, I appreciate your comments!  I am learning a lot, whether I need to know it or not.   ;)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 24, 2018, 11:26:33 AM
            I appreciate everything you said, and no I am not in a hurry, after all its doing the stuff to the console that is the enjoyable part, once its all done it will provide lots of pleasurable listening which is so rewarding in this particular hobby versus say stamp collecting. but you wont be disassembling it down to nuts and bolts any-time soon for a second time. With this 30 minute time limit with these new computers at the Marriott I've been staying at the last week or two, I feel rushed and probably sound rushed when I am typing because you lose twentyminutes of t-ypi=ng  Its timijng out now
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 24, 2018, 11:48:54 AM
Ed, there was a comment made earlier about our "over-thinking" this project.  That was the reference for my "in a hurry" comment. 

This will be a long, drawn-out process, like making the first batch of moonshine for the year.  One needs to be able to "sip" certain events, rather than "gulp."  Restoring this Stereo Theater is a "sip" event.   ;)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 24, 2018, 11:58:26 AM
    Oh that's OK I figured it wasn't for me, but it is true that I always look for most complicated solution to a problem and sure enough it is almost always the first thing all the advisors tell you to check. Like "are you out of gas?" "Is it plugged in?" "Is the fuse blown?"
     Darn, down to 2 minutes again. Was looking at the 1956, 1956A and 1957 Magnavox catalog and lost track of time. They really got into TVs those years. glad they didn't forget that hifi and radio was there big thinginn the longrun
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 24, 2018, 12:44:53 PM
    I meant their, not there.
           I wonder what a "newbie" who just got his first vacuum tube radio or console and is still mesmerized by the glow-in-the-dark vacuum tubeness of it all, I wonder what they want from the hobby. So many of them talk about playing I tunes through the unit, or even connecting a 70's Pioneer receiver to the speaker wires and skipping all the  built in electronics. Just the cabinet and external appearance is all they want.
          I would never change what is above the chassis, but I am not averse to disconnecting the original caps (but I will try to reform them first if they're not next to the 5U4 and 6L6s)and putting new ones underneath, but that is just me, I fully understand wanting the underneath to look original too.
           But who knows what a millennial wants ? They might strip it for their guitar amp, they might think the metal chassis should be spray painted psychedelic orange and sit on the sliding lids to be admired by one and all. And the worst of it is that they are the ones that stumble onto (for ten dollars) the rarest of the rare units that you may have been hunting down for years,   
           But what is it with Magnavox and the unbelievable wiring mess connecting all the units to each other ? That still amaaes me
 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 24, 2018, 01:20:21 PM
              So I'm wondering if that power transformer, while not matching the mounting holes, is still a genuine Magnavox component but from a slightly different chassis. The color coding of the wires matches the "alternate" color codes listed on later Magnavox chassis from the early sixties.
                  Instead of solid colors for all windings (not counting the center taps), only the 5 volt winding and the plate voltage windings are solid colors (yellow for 5 volt, red for 600 volt) while the two 6 volt windings and the AC primary are solid for one wire, striped for the other. That seems to be what your 9300 chassis has.
                I'm also wondering if the rectifier tube replacement socket was for an 8 pin relay rather than a vacuum tube. They are often a larger diameter than a tube socket which may be why only one screw held it in ?
            I hope you can use that big resistor and that it is really 100 ohms in parallel with maybe a leaky electrolytic which is why it reads 80 ohms.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 24, 2018, 02:22:28 PM
The colors of the wires on the PT match what it gives on the schematic.  Exactly.  Almost exactly, anyways.  The colors have faded somewhat.  The rectifier socket was Radio Shack cheap junk.  No doubt in my mind, as I've never seen a junkier socket in anything, ever.  It was destined for failure from jump street.  That big resistor will be replaced.  I've been thrown from that horse before.   ;)

My gripe today is suppliers.  Realizing that these guys are in a niche market and we should be grateful any of them exist.  That said, why do they not have what I need to complete my project all in one place.  Sal has the caps I need, but not the 5 watt resistor.  Radio Daze had the 5 watt, but are out of radial 33uf and 47uf 450 volt caps.  Just Radios does not have terminal strips.  So I have to make at least two orders for parts.  GRRRR.....
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on July 24, 2018, 07:02:28 PM
Mouser!  ::)

Sorry Greg, I just had too say that.

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 24, 2018, 10:48:21 PM
I'd considered them, Bill.  Too much hassle.   ;)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 25, 2018, 07:12:21 AM
I'm having cataract surgery in the morning.  This project will be on hiatus until that process is done. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 25, 2018, 07:45:43 AM
          hope the surgery is totally pain free and you recover fast.

         think of how much clearer the underneath of the 9300 chassis will be afterward !!
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 25, 2018, 09:24:41 AM
   I didn't even notice the color coding. Maybe I should get an eye operation !!     The Sams had the color coding like the original Magnavox service info, bu didnt have the resistances
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Alfista on July 25, 2018, 10:39:55 AM
I'm having cataract surgery in the morning.  This project will be on hiatus until that process is done. 

You'll be back on it tomorrow afternoon and we'll be cheering for you!

          hope the surgery is totally pain free and you recover fast.

         think of how much clearer the underneath of the 9300 chassis will be afterward !!

 There's a great chance of both. And good point Ed, those PT wire colors might not be as faded as they seem to be. The new, clear intraocular lens may correct refractive errors, bit will definitely let brightness and color through that the cataracts have been obscuring.

Good luck, Greg!


-Tim

 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: SeniorSteve on July 25, 2018, 11:05:42 AM
I read through many of the threads on here and enjoy every one of them.  The banter back and forth is amazing, both the information given out and the helpful way it's done.  I really should be more of a poster, but you guys answer all of the questions so fast, it's hard to do.

I hope to be able to help in the future.

Steve
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on July 25, 2018, 12:08:38 PM
Never feel afraid to jump in Steve. You may see something the rest of us are missing so your input is important.  Part of my enjoyment is reading everyone's comments, technical or just talking about anything.  It's a way to have friends that share a like interest. 

All the best tomorrow Greg!

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 25, 2018, 01:56:34 PM
Thank you all for your kind words!   :)

Another set of eyes never hurts.  I'm glad you guys are having fun with this project.  I was beginning to wonder if I had worn out my welcome with this thread.  I hope you guys will help me out on this with your input, whenever you feel like offering it. 

Earlier, Ed mentioned the MPX adapter and asked how I polished it out.  He thought I had the touch with a rag.  When I was in the auto restoration business, a specialty I had was polishing the brushed aluminum tail fin trim on '57 Chevys and 58 Buicks, mainly, with some models of Oldsmobile and Pontiac thrown in.  Mostly 57 Chevy and 58 Buick trim.  One learns that you get only one shot with that stuff.  It is either breathtaking when I was done, or total garbage with no hope of salvation.  The difference was touch.  How hard and in what direction I polished.  On that MPX, I started out with lacquer thinner to get rid of the tar and nicotine.  Nothing else cuts that stuff so you can polish.  Then I used 320 grit sandpaper, dampened with PB Blaster.  Then 0000 steel wool dampened with PB Blaster.  Then a rag dampened with PB Blaster.  After everything sets a week or so, I'll wipe it all down with lacquer thinner then polish with my Dremel and Simichrome polish.  After I get the shine like I want it, I'll probably preserve the shine with another thin coat of PB Blaster.  Wonderful stuff, that. 

Before I get the lecture about not using steel wool around electronics......

This is the way I was taught to do it.  I always use a stabilizing medium of some kind to keep the shards under control, PB BLaster, Simichrome, something.  I stay away from transformers.  Then when I'm done, I blast the waddin' out of it with compressed air.  I don't get silly with the pressure, only 30 psi is all you need.  Just be thorough.  I use common sense and it works great for me.  You do what you feel comfortable with.  Ed asked, so take this for what it's worth.

PB Blaster is the only stuff I have seen that will keep the white cad plating dust on Magnavox chassis under control.  Magnavox uses high-nickel steel in chassis and they are gorgeous when they are cleaned and lightly polished.

I have one of my (in)famous backs in production for the Stereo Theater.  I need lots of reflection and sparkle.  So I am trying to find all the clear-top tubes I can for the various chassis and want to polish everything I can to add to reflection and sparkle.   :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 25, 2018, 02:50:31 PM
           I am always ruining things unintentionally;  one reason is I think I am polishing one kind of metal and it's a while different metal. the same with wood. and bakelite is a whole monster in itself. I should practice on an invisible part of the cabinet but I always realize too late that I am making a major mess.

          One thing I have done that seems to work best with things like a porceleine (can't spell it)sink in a bathroom with lots of dripping water calcium on it. Assuming no one has tried Comet or BonAmi on it, I smear clear thick oil on it then take a brand new single ended razor blade, and gently scrape back and forth at a 45 degree angle digging into the sink and gradually work my way towards the calcium area never pushing hard enough to do any-thing but glide smoothly and harmlessly over the good part of the sink. As you slowly reach the calcium 1/64th inch at a time, you will feel the sudden scraping through the calcium, but you are still pushing no harder than what would be merely gliding over the oil in the good part. Eventually you will have gone through all the calcium. This also works on the chrome or steel parts of the drain.   
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 25, 2018, 03:04:37 PM
      It also works well on really hard wood finishes like on a Telefunken table radio\ with that shiny glossy shellac (?)  surface. It can work with varnished wood but you really have to practice on an unmessed up area first. It is particularly good with otherwise pristine finishes that have been near a spray painter like when you get a radio from a painter who used it to listen to as he spray painted nearby. those teeny hemispherical spray dots will come right off and the more you do it the better you get at the angle and the pressure to use. It's not so good on stained but unvarnished wood cause the razor tends to dig in no matter what the angle or pressure.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 25, 2018, 05:45:15 PM
         I have seen the stipe on one end of power transformer windings and now that I think of it they would usually only be on more modern equipment say the late fifties or later, especially on TV sets. What puzzles me on the Magnavox transformers is that the center tapped HV winding has both ends solid red and the same goes forth rectifier filament, both are solid yellow. However the AC primary and both 6.3 volt filament windings have one side of each winding striped and the other side solid.
            The only reason I can think of is something to do with Underwrites Laboratories regulations, maybe the striped side of the primary is the outermost part of the winding, but why the 6.3 volt windings and not the 5U4 winding.  Another possibility might be that they are thinking of the possibility that the designer might to use one or both of the filament as a boosting or bucking winding to raise the 121 volt primary to a 127 volt primary or reduce it to a 115 volt winding. Or maybe you might put the two windings in series with each other to make a 12.6 volt filament winding or parallel them to make a heavier current 6.3 volt winding.
           I hate to theorize about any this as the last two problems I was trying to suggest a solution for, have turned out to be extreme cases of looking for a complicated solution and ignoring a very simple solution that turned out to be the real solution, and I had egg all over my face. The parasitic oscillations and the miswired power transformer come to mind and I know there were a lot more not as recent so my feeble mind has mercifully deleted them from memory !!
           
     
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on July 25, 2018, 10:57:29 PM
           I

          One thing I have done that seems to work best with things like a porceleine (can't spell it)sink in a bathroom with lots of dripping water calcium on it. Assuming no one has tried Comet or BonAmi on it, I smear clear thick oil on it then take a brand new single ended razor blade, and gently scrape back and forth at a 45 degree angle digging into the sink and gradually work my way towards the calcium area never pushing hard enough to do any-thing but glide smoothly and harmlessly over the good part of the sink. As you slowly reach the calcium 1/64th inch at a time, you will feel the sudden scraping through the calcium, but you are still pushing no harder than what would be merely gliding over the oil in the good part. Eventually you will have gone through all the calcium.   

Here's an easy way to deal with calcium:  plain old white vinegar.  One of my boats used to have a dull area about 18" up from the waterline after a season on the mooring.  I used to muscle through it with an abrasive-based polish, on the assumption that the gelcoat was going dull.  Then a light went off--maybe it's calcium?  I rubbed at it with some vinegar.  After a few seconds I could feel it melt.  I buy the vinegar by the gallon at Ace Hardware, but the grocery store is another source.  Miracle stuff; great for mildew too.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on July 26, 2018, 06:08:00 AM
White vinegar is a miracle product.  There is a book written for the uses of vinegar, both practical and medicinal.  I use it to clean the calcium from my humidifier. 

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 26, 2018, 01:32:46 PM
I survived eye surgery.  I'm not sure I'm better, but I'm not blind, so we fought this one to a draw.  I need to get the other eye done to be back to normal.  My balance is off and everything is out of focus.  They say this will get better.....

The surgery only took a few minutes.  I was out the whole time.  I don't remember the doctor coming into the operating room.  We go to the hospital at 6:45 am and were sitting at McDonald's eating breakfast at 8:55. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: SeniorSteve on July 26, 2018, 03:40:51 PM
Electra225, I've had several good friends have the cataract surgery.  One in particular had to have it because of his diabetes meds made the corneas very cloudy in two weeks, he went from ok to drive to almost completely blind.  After the surgery, he could see very well far away, but now has "cheaters" laid all around the house.  I think he was very happy with the outcome as he had been wearing glasses since age 12 or so.  Everyone is different in recovery, so take a deep breath and let the healing continue.  I've had glasses since age 10 or so and am too nervous about getting lasik done, so much that it's going to be when I HAVE to, or replacing the corneas (cataract) surgery.  I have been wearing glasses for 54 years, why stop now?

Bottom line is I hope your sight gets better fast! 
An advanced "Good luck" with your other eye.

Steve
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 26, 2018, 03:53:55 PM
The procedure went exactly like the doctor said it would.  I'm looking forward to the benefits.  My wife had the procedure by this same doctor two years ago and she got along well.  She had astigmatism really bad.  She still wears glasses, but only for watching TV and driving.  Maybe after I get to where I can read road signs again, she will not have to wear glasses at least when I'm driving.  I don't have glaucoma or diabetes or any of that, so the doc thinks I may get by without glasses at all.  I'll be satisfied with thinner lenses and getting rid of that horrible glare.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Alfista on July 26, 2018, 04:42:16 PM
I need to get the other eye done to be back to normal.  My balance is off and everything is out of focus.  They say this will get better.....


 Did they remove the corresponding lens from your glasses? Your old Rx will get in the way after the implant. Any optician (like me) should remove that lens for you in just a minute at no charge. That can help with balance and focus, unless your post-op Rx is very similar to your previous Rx (not likely).

The durezol, et al., will help with swelling. Once that subsides and the drops don't interfere, your vision will be better. I see it virtually every day. 8)

Hang in there!


-Tim

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on July 26, 2018, 04:59:15 PM
We have an optician in the forum family.  :)  You can give advice for all us old people that have old tired eyes.  ::)  I have had glasses since Kindergarten, that's only 62 years.

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 26, 2018, 05:43:12 PM
They left my glasses like they were.  I could not use them at all if I had both eyes done.  The doc gave me a choice of keeping my old glasses or wearing some kind that looked like a decrepit old guy.  I decided to keep the ones I had and just look fuzzy for a spell.  When I get the left eye done, then we'll figure out what to do about glasses, if any.  I'm fully expecting to have some type of corrective lens going forward.  Either for far off or for close.  Plus Transitions so I don't have to buy ( and lose!) sun glasses.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Alfista on July 26, 2018, 09:23:55 PM
  You can give advice for all us old people that have old tired eyes.  ::)

Bill

Anytime, Bill!

Greg - Hopefully you'll just need readers. That's par for the course and a cheap fix. BTW, Transitions aren't as great as they seem. They work great everywhere but in the car, the UV inhibitor in auto glass keeps them from working behind the windshield. You'll still need sunglasses for driving  :(

-Tim
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on July 27, 2018, 11:49:06 AM
Thanks Tim, I just learned something about transitions and cars.  I have never had them but was thinking (always used clip on type)  with my next pair of glasses I would get transitions.  I have an eye appointment on Monday, as my right eye sees fine for distance but my left seems blurry.  I ware trifocals,  progressives don't seem work for me and I'm fine with that.

Thanks again for the tip.

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 27, 2018, 12:25:01 PM
If this all works out like it has started, I may need reading glasses.  The doc wants me to get prescription sun glasses in place of Transitions.  I personally like Transitions and have had good luck with them.  The doc is more concerned about UV and glare.  He believes OTC sunglasses are lacking therein.  It might be sales hype, though.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 27, 2018, 04:54:07 PM
   For the last ten years or so, I have been visiting an 89  year old blind man and I know his entire family very well. Usually I would visit him Tuesdays, so his wife could meet her friends for bridge, Thursday, and Saturday. This visiting coincided with me going part time at my job and my brother and sister staying with my 89 year old mother.  Being around him for six or seven hours at a clip has given me an entirely different outlook on life. He is so blind, he can barely see a faint r of light to the side when h looks directly at the sun.
         Even if I fell down an elevator shaft and broke both arms and legs, I think the first thing I would think, when I could think at all,  would be, "Thank goodness I still have my sight."  I still do my share of complaining, I guess that is a wired-in function. When this motel computer resets on me just as I am about to the post key after twenty minutes of typing, I could crumble the keyboard to dust.  Sometimes the guy is so short-tempered and grouchy with me I almost blurt out, "You know, you deserve to be blind"  but thank goodness, the words catch in my throat before I utter them, thank goodness.
         Anyway, I have glasses just like I first got in seventh grade and I've never considered vision correction or even contact lenses because I just hate to even barely risk some unknown side effect coming to goof something up twenty years later.  So everybody thank your lucky stars for even the blurry sight you have. Trust me on that. Now I have thirty seconds to post !! Again !!
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on July 27, 2018, 06:19:02 PM
Since we're talking spectacles and cars, as so often happens, I'll add something.  I've got the progressive lenses--the ones where you've got reading/closeup correction at the bottom and distance vision at the top.  It's the modern version of bi- or trifocals.  Once you get used to them, they're great.  Until, that is, you crawl under the car and look up.  Then, the proper correction is in exactly the wrong place.  @#$*&!!!  I have read that some people who often work in that posture will get a pair of glasses with the correction reversed--upside-down.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: walyfd on July 27, 2018, 06:51:54 PM
Since this thread seems to be on a "hiatus", I'll respond...

My Aunt Camille always took off her glasses to thread a needle or read something up close.  She told me I'd do the same thing someday...  she was right.  I now have trifocals and still take my glasses off for detail work.

We ALL become our parents and ancestors.  It's genetic and inescapable.  I'll always remember the day I was in the house alone (I was maybe 15 and won't say how long ago that was) and walked down the basement steps.  I swore my dad was following me...  nope, it was ME, alone...

Later on, my mother thought it was him as well...  he was in bed and I went downstairs for something.

It doesn't bother me anymore.  Makes me happy to hear both our footsteps...
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on July 27, 2018, 07:50:08 PM
There was an old guy in my town that painted houses, both inside and out.  He had a pair of glasses in reverse.  One for looking up and one for looking down. 

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Alfista on July 27, 2018, 08:28:18 PM
If this all works out like it has started, I may need reading glasses.  The doc wants me to get prescription sun glasses in place of Transitions.  I personally like Transitions and have had good luck with them.  The doc is more concerned about UV and glare.  He believes OTC sunglasses are lacking therein.  It might be sales hype, though.

Transitions do offer full UV protection, but if you end up with no distance correction, that's moot. Be aware you can get them in bifocal with no corrective power on top, just reading in the bifocal.

My distance Rx is nil, but my grey hair demands reading assistance. Therefore I wear a bifocal (progressive) full time so I'll always know where my glasses are.

In regards to OTC sunglasses, there are good ones and they aren't cheap. RayBan makes good lenses, as do Costa De Mar, Persol, Oakley, Maui Jim, Smith Optics, etc. Their optical quality is very good, material and build quality is too. Wrap designs gave a but of base-in prism ground in to compensate for the wrap angle, and there's no unwanted astigmatism. You can depend on the UV and polarization to be accurate from these vendors.
 In addition, Costa Del Mar has a selection (C-Mates line) of their models with a 28mm reading segment in the bottom. Good quality polarized lens, and less expensive than having one made for you. Other quality brands may offer this feature as well.
 Cheap sunglasses are truly just that.

One last point, your insurance likely offers to pay a portion of the first pair if glasses after cataract extraction. It is a medical benefit, even Medicare covers the base charges. Sunglasses are not excluded from this benefit as long as they come from a provider for your insurance plan.

- Tim
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: SeniorSteve on July 27, 2018, 08:47:54 PM
I've had the transition and progressive lenses for my last two pair of glasses.  I know my sight is changing, but I do know that my next pair of lenses will be a straight line bifocal.  I'm willing to try them as I'm so tired of trying to find the "sweet soot" in the progressive lenses.  If I turn my head slightly off axis when watching tv, it's like the convergence went bad on me.  Doesn't matter which side but what's interesting is, the blue and red "misconvergence" I see is reversed depending on which side of the lens I'm looking out of.  My sight is pretty bad (I was told I'm legally blind without glasses - I think something like 20/400), along with strong astigmatism makes me not want to mess with them.  Yes, I can usually see and read tiny writing with my glasses off and almost next to the eye.  That's changing and I'm using a magnifying glass more often now.  I also have two LED shop lights above my bench as I need light, and LOTS of it.

Steve
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 27, 2018, 09:02:18 PM
I appreciate you guys jumping in here.  However.......this is a Stereo Theater thread and we probably should say something about my ST
 lest a moderator puts an end to our little OT chat.   ;)

I need a quad of output tubes.  I have used JJ's in the past and decided to try something different.  I have been considering the Tung-Sol re-issue tubes.  Check out the listing.  Scroll down to the last customer review.  Where do they come up with this stuff.

Scroll on down to the questions.  What is a "medium boogie" and why would anyone need/want one?

https://www.tubesandmore.com/products/el846bq5-tung-sol
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 27, 2018, 10:27:30 PM
   I just finished looking at Mesa Boogies web site. I thought they only made guitar amplifiers but they also carry an entire line of tubes and they discuss them in guitar amp terms and also hi-fi amplifier terms too. The guitar amp terms made me do a lot of eye-rolling, not to mention eyes again but when you see 5U4 rectifier tubes as having a "creamy" sound you begin to wonder.
     Anyway, they list a lot of output tubes including EL84, plus dual triodes like 12AX7 and rectifiers. They say they are "selected" without giving any selection criteria but I imagine the plate current at certain plate, screen grid and control grid voltages is one of the main specs but the-y don't talk about any scale. Other points like low grid emission and maximum current available at normal filament voltage might also be specs. They mention that they are designed for fixed bias circuits which may mean the tube is stable with no cathode resistor providing feedback and a high value grid resistor from grid tgroune
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 27, 2018, 10:50:06 PM
     It looks like they carry tubes in singles, matched pair and matched quad sets so someone with a quad Magnavox 6V6 bi-amp circuit is in luck. They select them for you and you don't have to have a collection of 6V6s to do your own matching.
      Hopefully their matching checks the currents at slightly higher and lower filament voltages too and matches the tubes to track each other over a filament voltage range instead of at only 6.3 volts. The "life" test on some Hickok tube tester reduces the filament voltage a bit so you can see how much the transconductance reading drops off after throwing the switch  I have noticed that a seeming good tube may drop off sharply after throwing that "life" switch and another one will hardly change.
          Some tubes that are slightly gassy will track each other pretty good in a circuit with 100 kiloOhms resistors in the grid circuit but will track  poorly in circuits with a really high value of grid resistor like 1 MegOhm, which is the maximum resistance recommended in the grid circuit, and that is for cathode bias only, fixed bias is 300 kiloohm maximum.
         It is truly a pleasure to see all these recent instead of vintage advertisements for vacuum tubes although it negates years of hoarding older ones going on the assumption they would never be made again.
             I understand that you can build an entire Model T from all brand new parts because they are all, repeat ALL still being made new. Even the frame and body !
         
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Alfista on July 27, 2018, 11:00:02 PM
I appreciate you guys jumping in here.  However.......this is a Stereo Theater thread and we probably should say something about my ST
 lest a moderator puts an end to our little OT chat.   ;)


 Agreed, sorry to have taken over your restoration thread! (If a mod wants to move the OT posts into the chat forum, I'd be happy to answer questions and offer advice.)

Glad to see you're back into the ST! I'll be learning vicariously through your experience before starting on mine ;D

     Anyway, they list a lot of output tubes including EL84, plus dual triodes like 12AX7 and rectifiers. They say they are "selected" without giving any selection criteria but I imagine the plate current at certain plate, screen grid and control grid voltages is one of the main specs but the-y don't talk about any scale.

Ed, I think their "selection" criteria are parameters optimized for operation in Mesa Boogie amplifiers. I'm not convinced their matching process is as applicable for HiFi use.

-Tim
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 28, 2018, 04:05:31 AM
       That may well be but I hope not because if they need some unusual tube characteristic not specified in a tube manufacturers description of what they test their product for, they are more or less stuck with the tubes they get.  I guess they could insist the tubes would pass a special test and make their acceptance of the shipment conditional on passing that test. It may be that they were having problems with the sound or measurements on their amps until they started custom ordering their own tubes.
       Guitar amp users believe in their ears judgement over other people's measurements and they are fully justified in this because so many times has their unexplainable preferences for certain circuits or types of equipment been borne about by later knowledge, for example their passionate preference for the older tube amplifiers over the then new transistor amps in the sixties. I believe its a duty of the circuit designer to figure out wh-y the-y want this or that instead of claim its nonsense
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 28, 2018, 05:38:59 AM
   Guitar players have their opinions and their own vocabulary to describe what they hear. And I don't mean mellow or harsh, words you might expect to describe what something sounds like. I mean words like fat, creamy, tight, liquidy. Some of them wind their own pickup coils and that's another black art, the winding technique. There are black magic designers of audio circuits too. In their web sites they usually have a healthy dose of ego, claiming their moderately expensive circuits "blow asway" the super-expensive high end amplifiers in blind comparison tests.
      I  never could understand why amplifier designers won't even apply the precautions recommended by the makers of the vacuum tubes themselves. If they are smart enough to successfully design and produce the actual tubes, can't we follow their recommendations as to what circuits they want them used in ? It's a pleasure to take apart and inspect really reliable high quality test equipment or radio equipment. When a maker of radio station audio gear has been in business for 40 years without a lemon having to be recalled and modified, with the same model in production for many years, they must know what they're doing, and they all use the recommended circuits for their designs. You don't have to select replacement tubes or add your own modifications to get it to work right.
       Another black art is when people buy expensive capacitors or resistors, substitute them in their equipment and make audio judgements as to the sound qualities of these components without trying to figure out what aspect of the components spec might be causing the difference in sound. There is always a reason why.
       
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 28, 2018, 07:32:25 AM
Tim, you have a Stereo Theater?  How about sharing some pictures.

What I can say, from what little I have delved into mine, is that Magnavox went to great lengths to build a ST out of parts already on the shelf.  The tuner in mine is unique, apparently, to 1962 Stereo Theater models.  I still have not figured out why.  It is a 77-03-00 model, specifically.  It looks like a 5700 series tuner with one more 6EU7.  The tuner in my ST is not designed to be removed.  Instead of removing the bezel and knobs and pulling the tuner from the top, this tuner comes out the bottom.  The rat's nest of wires needs to be removed or contained in order to do that.  The bezel appears to be part of the cabinet.  I see it is possible to change the tubes in the tuner without removing the tuner from the cabinet, a Magnavox vertical tuner first.  Everything else I see is a component used by another Magnavox instrument. 

"Gloriously Complicated"

Magnificent instruments, these.  Massively overbuilt, yet so simple.  Wires going all over the place, but fairly easy to follow and figure out what they do.  Speaker connections easy to derail, then get connected back wrong.  Easy to remedy.  Beautifully built cabinetry with pocket screws.  If you find particle board in the bottom of a Magnavox cabinet, it is there for purposes other than lower cost.  It actually cost more for particleboard like Magnavox used than it would have for plywood.  Magnavox used particleboard in open speaker enclosures to prevent the cabinet from drumming.  It was low-density material made specifically for speaker enclosures.  The problem I see with it is that it deteriorates and starts shedding its particles.  Mine is pretty bad.  I either need to replace it or figure out a way to stabilize it so it does not come apart.

Anyone servicing or restoring one of these old ST's should be prepared to go over every single component in the cabinet to make sure it correct.  The ones I have seen appear to have had a hard life.  Even ones that look like new have been butchered in the electronics.  The only reason I can think of is that these things were typically serviced in the customer's home.  They were too heavy to haul back and forth to the shop.  Service people did the minimum to get it going then put the back on and collected the bill.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 28, 2018, 08:46:28 AM
         Probably the audio parts of the stereo theatres were still serviced by TV repairmen, especially if the only symptoms were totally dead set. I doubt if the owners realized that their instrument was basically an elaborate stereo hi fi that had a tv chassis added to it. Most lesser brands would consist of a console TV with an FM-AM chassis grafted into the TV's audio . The phonograph would be grafted into the FM-AM audio. The TV repairman would not be so familiar with a power amp chassis especially a bi-amped Magnavox.' 
      As far as I know, all the JBL cabinets were some kind of particle board and it was chosen for its highly damped non-resonant properties. I had a mid fifties JBL "Harkness" rear loaded bass horn that took the 15'" woofer and the horn and driver with the  acoustic lens. It was very thick, very heavy  and very dead sounding when you rapped on the sides. There was a blondewood veneer. It was anything but a cost-cutting measure. You had to be careful with the wood screws as too many tightens and loosens would chew up the particle board. The cabinet had a lowboy and a highboy version, mine was a lowboy.
     
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Alfista on July 28, 2018, 12:00:42 PM
Tim, you have a Stereo Theater?  How about sharing some pictures.

What I can say, from what little I have delved into mine, is that Magnavox went to great lengths to build a ST out of parts already on the shelf.  The tuner in mine is unique, apparently, to 1962 Stereo Theater models.  I still have not figured out why.  It is a 77-03-00 model, specifically.  It looks like a 5700 series tuner with one more 6EU7.  The tuner in my ST is not designed to be removed.  Instead of removing the bezel and knobs and pulling the tuner from the top, this tuner comes out the bottom.  The rat's nest of wires needs to be removed or contained in order to do that.  The bezel appears to be part of the cabinet.  I see it is possible to change the tubes in the tuner without removing the tuner from the cabinet, a Magnavox vertical tuner first.  Everything else I see is a component used by another Magnavox instrument. 


 The first thing I did with mine was spend a few days staring at it, to figure out what all I was looking at. Mine has the smaller TV, 5 knobs and the 12" 8-speaker system, 79-08-10 tuner/preamp, MPX, 93-04-10 amp. I came to the same conclusion about parts, this must have been the end of tube unit production and they were cleaning off the shelves to make room for the new technology, so anything goes. The bones of ours are very similar, the layout, cable-driven channel indicator, lighting, remote. I look forward to seeing exactly what is inside your cabinet.




Magnificent instruments, these.  Massively overbuilt, yet so simple.  Wires going all over the place, but fairly easy to follow and figure out what they do.  Speaker connections easy to derail, then get connected back wrong.  Easy to remedy.  Beautifully built cabinetry with pocket screws.  If you find particle board in the bottom of a Magnavox cabinet, it is there for purposes other than lower cost.  It actually cost more for particleboard like Magnavox used than it would have for plywood.  Magnavox used particleboard in open speaker enclosures to prevent the cabinet from drumming.  It was low-density material made specifically for speaker enclosures.  The problem I see with it is that it deteriorates and starts shedding its particles.  Mine is pretty bad.  I either need to replace it or figure out a way to stabilize it so it does not come apart.

 Yes, the furniture quality construction is why I was able to bring it home. The WAF was so high, she actually found it at an estate sale and asked to get it. Already having tons of unneeded stereo equipment, I pounced quickly before her mind changed. A one-owner unit, still in the home is was delivered to when new and they were glad to get $35.00 for it. The cabinet is excellent, no work required other covering a few light scratches. Particle board bottom is covered in dust, but still in great shape having spend its entire life in a living room.

 As daunting as the wiring appears, everything is modular so that simplifies it a lot. The external connections and switches are likely to be the worst of it. I spent 15 years doing car audio in my previous life, back in the 80's and 90's when multi-channel systems were created by us installers using 2 channel amps and outboard signal processors, so I've seen worse!

 At this point, it has only been used decoratively. My plan is to go through the amp first, then the preamp/tuner, and then the changer. I don't plan on doing any mods, only replacements. I have plenty of other stuff to play with, and am gathering components for a 25W class A solid state build as my next thing.

Anyone servicing or restoring one of these old ST's should be prepared to go over every single component in the cabinet to make sure it correct.  The ones I have seen appear to have had a hard life.  Even ones that look like new have been butchered in the electronics.  The only reason I can think of is that these things were typically serviced in the customer's home.  They were too heavy to haul back and forth to the shop.  Service people did the minimum to get it going then put the back on and collected the bill.

 Agreed, that's the only way to know what you have!

-Tim
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Alfista on July 28, 2018, 12:06:36 PM
This model is a 4MR357R, estimated 1962.



-Tim
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Alfista on July 28, 2018, 12:13:00 PM
Last 2 pics - 4MR357R
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 28, 2018, 12:39:59 PM
Yours has the 24" CRT with a version of the Symphony electronics, with its eight speaker system.  Wonder why the Stereo Theaters in 1962 only got 12" speakers when the older ones all had 15".  You are probably better off with a 24" TV as they are more common than the 27" is.  I'm told by someone who should know that Magnavox TV sets are not as bad as some claim they are.  It is basically like mine with the exception of the CRT and the tuner.  Your cabinet may be a couple inches shorter, but that is in your favor.  I have a set of 15" Magnavox speakers, so I may attempt a transplant.  I don't see any reason they would not fit or work just fine.  The speaker and antenna connections on plastic brackets, mounted to a cabinet upright is a long-overdue touch found on the '62 and newer instruments.  My little 2ST253 stereo has those. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Alfista on July 28, 2018, 03:53:38 PM
Unless the TV is an easy fix, I'm not likely to get into that repair- too many other projects that are more interesting to me. 25WPC class A SS amp, a turntable to finish and one to start, a couple of pairs of speakers to build, lots of repairs, etc.

 The 1962 12" woofer question is curious. Do the Astrosonic models with horns also use 12's? I thought I'd seen them with 15's, if that's the case, your 12's really don't make sense. I've also considered changing out the 8 speaker system for the horns, but not if that requires any permanent modifications. In your case, the crossover values would probably still work OK, so it would only be a matter of fitting the 15's in place.

-Tim
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on July 28, 2018, 07:02:58 PM
That's a nice looking ST Tim.  I can see why the wife liked it.  :)

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 28, 2018, 07:43:58 PM
I have the horns and speakers from an Astro-Sonic Stereo Theater.  The big speakers are 15".  I believe it had the 100 watt amplifier.  I intend to get the TV set working in mine.  An idea I had was to take mine to AZ after I get it done and use it in my den there.  I could watch Perry Mason OTA, which I cannot do here.  I have a converter box there.  The fiber optics system we have here is just not compatible with any CRT set, let alone older ones. 

The eight cone speaker setup was only used in the Symphony models and in the Stereo Theaters that used the Symphony's electronics.  I like the way mine sounds.  I'm not sure horns will sound better.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Alfista on July 29, 2018, 10:19:12 AM
I could watch Perry Mason OTA, which I cannot do here. 

LOL! Down here between the cow pasture and cotton patch, we got tired of paying for satellite TV. Now we watch Perry Mason every night OTA on MeTV, and the B&W westerns on Saturday. It would be neat to watch on the Mag.

Do you plan to leave the 12's in place at first, then try the 15's? The smaller woofers may actually have better, less directional midrange and mate better with the horns as a two-way system. I'm eager to hear my Symphony speaker system in action, hoping all the speakers are in good working condition.

So, are you back to hands-on work yet?

-Tim
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: walyfd on July 29, 2018, 01:59:30 PM
We NEVER had cable.  Mom always said if you want it, you pay for it...  I think it's fine if you're home all day but I'm OK without it.  We had 4 channels when I was a kid--5 if you count channel 12 from Binghamton that was a second CBS station.  Today, we have about 25 antenna stations.

A few weeks ago, I got a new HD antenna and mounted it in the attic.  Rain and wind affected the one I had on the eave.  Also ran all the coax inside the walls...  that was not fun...  still patching and painting walls...  anyway, it was worth it.  No more drop outs and I can run up the attic to adjust the antenna.

If you have MeTV, look out for "77 Sunset Strip", "Mr. Lucky" and "Peter Gunn".  I'm up at 5 AM for work and catch the Mancini-themed shows...  nothing like Lola Albright and the PG theme to start your day...
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 29, 2018, 02:13:35 PM
Here in downtown Bugtussle, we used to get a couple channels out of Springfield on the antenna.  No such luck with digital.  We have fiber optics, which is good, but goes up on price nearly every month.  We are considering going back to Dish.  Dish promises me a full screen on my older CRT set, something I can't get anymore with fiber optics.  I'd have to have a modulator on this old Magnavox before I could even get a partial screen picture.  That is too much hassle.  The converter box I have in AZ will give me a full picture on the old Magnavox and I can get MeTV OTA.  Channel 7.2.  There are alleged to be over 60 channels in Phoenix available OTA. 

I'm not back to full time servicing yet.  The doc wants me to avoid "noxious fumes" whatever that is.  I guess soldering and lacquer thinner are in that class of irritants.  I can hold off a bit in order to make my eye surgery successful.  I am into full time tinkering at this point.  I have been playing with a little GE stereo I got recently and I got caught up on "honey do" stuff around the place. 

I am going to try the 15" speakers at some point just because I have them.  I have nothing really to lose by trying them.  If they sound better, or sound the same, they probably will go in.  Worse, the speakers stay 12".  Nothing will be hacked or changed except the grill cloth.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on July 30, 2018, 05:50:47 AM
The people I know that have Dish got a really good deal for 2 years and then the price doubled and continues to go up. No matter what you have for a service you have 200 plus channels of nothing to watch, and we pay for that.  :(

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 31, 2018, 08:45:41 AM
There was a snafu with my parts order.  I have waited for almost two weeks for parts that will never arrive.  I hate online ordering.  Nobody is accountable, nothing gets resolved.  My project is in limbo because a business needs to save money.  In the future my rule is no phone number, no money from me.  Rant over.

I took the interim period to do some cleaning up of the electronics on the amp.  I got rid of the taped joints by soldering and using heat shrink on them.  I revamped the power cord in preparation for installing a fuse.  I checked resistances on everything and ran the wiring against the schematic one more time.  I believe I'll be good after I replace a few caps and some resistors.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on July 31, 2018, 09:29:36 PM
Sounds like a lot of progress Greg. All you need is parts supplier cooperation to proceed.  :)

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on July 31, 2018, 10:05:51 PM
There was a snafu with my parts order.  I have waited for almost two weeks for parts that will never arrive.  I hate online ordering.  Nobody is accountable, nothing gets resolved.  My project is in limbo because a business needs to save money.  In the future my rule is no phone number, no money from me.  Rant over.


I ordered a bunch of electrolytic caps from Mouser last winter and just got the balance of my order last week.  I think that the values and styles we tend to seek (in my case, axial leads) may complicate matters.  By ordering I hope to maintain enough demand so they'll keep buying them from their suppliers, who will keep making them.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: danrclem on July 31, 2018, 10:15:12 PM
If you have a small order, not in a hurry and don't want to pay for shipping Digi-Key is the way to go.  They do however charge sales tax but that's still not a bad deal.  I did this one time and it took a little longer to receive my order but I wasn't in a hurry.

6. Shipping Charges. Except as otherwise provided on the Site, (1) shipping or freight charges and insurance will be paid by the customer*, (2) all sales are made FOB Digi-Key's warehouse in Thief River Falls, MN, USA, and (3) shipping or freight charges from Digi-Key's warehouse in Thief River Falls, MN, USA are prepaid and added to the invoice, billed collect or billed to a third party. Shipping Cost Estimator
* When a check or money order accompanies your order, Digi-Key pays all shipping and insurance (our choice for method of shipping) to all addresses in the U.S. and Canada.
Shipments of excessive weight or size may require additional charges. Digi-Key will notify you prior to shipment if these conditions exist.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 31, 2018, 10:39:15 PM
I'm not necessarily in a hurry, but I hate waiting for parts.  Especially when I'm not going to get them.   ;)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 01, 2018, 02:12:20 PM
The parts situation may have been fixed.  Thanks, Bill!   :)

The picture tube in my new old Stereo Theater tests "Old".  Or to put it in TV guy lingo, I have a "bum jug."  On my B&K 445 tester, 300 is the minimum for a good picture tube.  My picture tube has been on the tester for two days and one night and will barely make 150 at 6.3 volts filament voltage.  If I increase the filament voltage to 8.4, it barely makes the "Good" range.  That is more voltage than a brightener would put on the filament.  So I need another picture tube.  I'm going to have the picture tube out of the cabinet so I can do cabinet work anyways, so I had just as well put a known good picture tube back in.  If anybody has a line on a good 27ZP4, I'd appreciate the head's up.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 02, 2018, 12:17:51 AM
I need to check with the moderators to see if a discussion of the TV set in my Stereo Theater can be done on this forum.  I'm not too wild about exposing my ignorance on VideoKarma, so this is my only shot.  I know absolutely zipkus about working on a TV if it has problems.  I have been watching YouTube videos until my eyes bleed and really know nothing more than when I started.  The guys on there make it look so easy.  I'm hoping we can talk about it on here, since the TV is part of the Stereo Theater, which is a console stereo.  Maybe I'm overthinking this...... ;)

My understanding is that, about the time this TV chassis was produced, manufacturers changed from using paper caps to plastic and ceramic disc ones.  They also used plastic caps that really had paper caps inside and are as needing of replacement as the paper caps were.  The caps in this TV set look like they are plastic on the outside.  How do I tell if they are the paper in plastic type that needs to be replace or the good plastic type that you leave alone unless you have a specific issue with one? 

I already know I have a bad socket on the damper tube.  One terminal is pretty badly deteriorated, so that socket has to be replaced.  Did a bad connection cause the terminal to burn and melt the socket, or do I have a problem in the chassis that caused the socket to burn and melt?  I don't have a schemetic yet, and that may answer some of these questions. 

The best advice I have read is to not worry about a weak CRT at the start.  Power up the chassis and see if a raster can be displayed.  Get the chassis working first then worry about a possibly weak CRT.  I'm simply not sure how to proceed with this.  My CRT tester condition is really unknown to me, since this is my first use of it.  It is possible that I have a perfectly good CRT and have a wonky tester.  That seems like a stretch....... ;)

I have to get my head around the safety aspect.  I'm still not comfortable messing with high voltage on the picture tube.  I hope there are some TV guys on here who can answer some of my questions.  I'm certainly going to need some assistance repairing the TV.   
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on August 02, 2018, 05:25:32 AM
I can't, and would certainly hope not, imagine that the moderators would put a stop to this thread.  This forum was founded to talk, restore, and preserve console stereo's with Magnavox being the headliner.  Having a Stereo Theater to add to the mix is a plus and I personally find this project fascinating and hope it continues.

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on August 02, 2018, 09:08:10 PM
Remember that the picture tube is a big capacitor after it has been operating, just in case you plug it on.  Discharge it to ground. I was lucky to learn about that the easy way (reading) instead of the other way.  And I've read that the black plastic tubular capacitors with colored stripes--"bumble bee caps"--are notorious for sudden failure.  Guitar amp builders prize them for the distortion they create (!!) so if you replace them, save them for offering on the auction site.  Thus endeth my contributions on the subject of TV repair.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on August 03, 2018, 05:47:24 AM
I learned the hard way, my arm tingled for two days.  ::)

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 03, 2018, 02:42:42 PM
I have been watching You Tube videos on working with picture tubes.  I just need to develop a "plan" like I did with working on radios.  A procedure that, if followed religiously, will keep me out of trouble.  I do not like learning "the hard way."  I've done that all my life in other things.   ;)

This set does not have any bumble bees that I have seen.  The caps in the TV chassis are either ceramic or plastic.  My only question is do I have the "good' plastic caps?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 03, 2018, 04:41:16 PM
This discussion may shed some light on the picture tube situation.  Fortunately, I have been hesitant to do anything but emissions testing. 

http://videokarma.org/showthread.php?t=270464

They talk about different models of B&K testers.  I wonder if this information applies to my 445.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on August 03, 2018, 05:13:30 PM
This set does not have any bumble bees that I have seen.  The caps in the TV chassis are either ceramic or plastic.  My only question is do I have the "good' plastic caps?

I just tried and failed to find my capacitor info collection.  One online site said that for the NOS black plastic ones (Cornell-Dubilier??), RED lettering/numbers  were good, yellow were untrustworthy.  I'll look for my info stash again.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 03, 2018, 10:46:20 PM
The caps in my TV chassis look like orange drop caps, only they are red.  They have fat bodies like orange drops do.  These have white lettering, I think.  This set was built about the time of the changeover from junk caps to ones that seldom fail.  Any help you can give that will answer that question would certainly be appreciated.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 04, 2018, 05:08:54 PM
I have been tinkering pending the arrival of parts.  I installed a fuse holder and a terminal strip for the cathode bypass cap.  I am now in the process of cutting the filter cap can in half so I can remove the old guts.  I want to restuff at least the 10uf and the 30uf caps.  The 40uf if there is room.  If not, it will go on the terminal strip with the cathode bypass cap. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on August 05, 2018, 08:14:58 PM
Progress is being made and sound is just around the corner.  :)

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 05, 2018, 11:50:49 PM
We'll forge ahead with fingers crossed.   ;)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 07, 2018, 12:07:58 AM
My Radio Daze order arrived today.  I can install the 100 ohm cathode bias resistor.  Still waiting on Sal's order to get here.  Tomorrow, I'm hoping.   :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 07, 2018, 03:29:12 PM
The mail lady brought my capacitor order this morning.  I went out to the bench and installed the filter caps.  Unfortunately, the bodies of the filter caps were too fat and the leads too short (using spaghetti tubing) for me to restuff the capacitor can.  Plan B was already in place for that eventuality.  I put all four filter caps on a terminal strip.  Not quite as neat as restuffing, but it should work fine.  I checked my work a couple times, made resistance measurements and am satisfied I have done all I can.  Power up comes in the morning.   :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 07, 2018, 04:33:32 PM
I could not wait until morning!

I went out to the shop and plugged everything in, making sure the TV set was disabled.  The TV chassis powers up via the tuner.  There is an outlet on the tuner for the TV to plug into.  The amp plugs into the TV chassis for power.  I disconnected the power for the TV at the tuner and plugged the amp in there. 

I have a 75 watt bulb in my dimbulb/Variac, and that is pretty light for this rig.  At first, I got nothing.  Zipkus.  I had voltage to the amp, but no voltage to any of the tube elements.  I got to looking and found I had not connected the power plug with the Molex connector to the MPX adapter.  This connection restored power.  The amp passed its preliminary, no rectifier, test.  No smoke, no noise, no extra heat.  The filaments and some of the dial lamps shone brightly.  A beautiful sight if ever there was one.  Next step is a slow power up with the rectifier in.  That will be in the morning.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on August 07, 2018, 06:57:13 PM
Congrats Greg, so far so good!  If everything goes according to plan tomorrow you will have music playing.  ;D  Keep us all posted.

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 07, 2018, 10:48:18 PM
Gloriously Complicated!   :)

We will keep our fingers crossed, think a good thought, and forge ahead.   ;)

Thank you for your encouragement, Bill.   :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 08, 2018, 01:43:18 PM
I'm going to try to remember the theme for this restoration, "Gloriously Complicated."   ;)

I have good news and bad news.  The good news is that the amp has passed its powering up with the rectifier in test with flying colors.  I have not checked voltages, but there is no smoke, no noise, less than two amps current draw and it did not blow its new fuse.  Pending voltage measurements and setting the cathode bias voltage, so far, so good.   :)

Now the bad news.  I still have a MASSIVE hum.  Ahead of the volume control.  MASSIVE, in that it rattles the speakers if you turn the volume up.  With the volume down, there is nary a peep or a hint of hum.  So I'd say my filters are doing their jobs.  There is no audio of any kind getting thru the tuner to the amplifier.  No AM, No FM, No FM AFC, No FM MPX, No phono, Nothing out of the tape input.  Just a massive hum.  The filter cap on the tuner chassis gets warm in one spot.  My next step will be to dig that tuner out, test tubes, replace those filter caps ( two 30uf@450 volt e-caps) and try to figure out what ails the tuner.  Now would be a REAL nice time to have a schematic, something that has eluded me thus far.  The schematics for the 5700 series is close, but there are things different in this tuner that I can see.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 08, 2018, 02:59:52 PM
More testing has revealed the following.

First off, I am really flying blind here.  I desperately need a schematic.  Apparently, this tuner does not exist.  I have not found a Sams for it.  However, referring to a 5700 series schematic shows that the two 30uf@450 volt e-caps in the tuner provide B+ for the 6EU7's in the tuner.  If I disconnect the two audio plugs from the tuner on the amp, I get no hum.  The hum is less, of course, when the bass control is retarded.  If the bass is on full, or the volume is very high, it motorboats.  That is a pretty good indication of a leaky cap somewhere.  I got the radio to work, in all positions of FM and in AM and I get a scratch when I rub on the needle in the phono.  The problem there (shock!) was a wonky Realistic Lifetime 6EA8 in the tuner that was not making good contact along with a really dirty function switch and bass control. 

The good side of this is that I have officially heard this thing speak.  A tad strangled, but speaking nonetheless.  A major victory.  I'm thrilled beyond description. 

We shall forge ahead, get this tuner out and onto the bench and see if we can discover what ails it.   :)

I am still powering the ST with my Variac, set at 115 volts.  I have run it maybe 20 minutes steady while I fooled with the tuner.  The PT in the amp ran cool as a cucumber and the audio sounds like it has reasonable volume and tone.  I'm guessing at this point we are going to be okay with the current PT.  I have no reason to believe it won't be just fine.   :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on August 08, 2018, 06:32:16 PM
Again congrats are in order Greg.  This is a huge step in the right direction considering it is "Gloriously Complicated."  :)  With 20 minutes of run time, and probably longer by now, without smoke it should be ok. It's amazing what baby steps and a few parts can accomplish.  ;)

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on August 08, 2018, 10:13:00 PM
On the hum, remember the rule about checking simple things first--tube sockets, connectors, then paper capacitors.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 08, 2018, 10:43:30 PM
I removed all the Radio Shack tubes except the 6EU7's.  I replaced them with RCA's with no change to the hum.  I wiggled the tubes with no change.  I need to get the tuner out so I can have a look see.  I have all the tube shields off so I can futz with the tubes.  That did not change the hum.  I wiggled wires in the rats' nest, no change.  My body touching certain parts of the instrument does not change the hum.  It is a steady hum, not tunable, and if the volume or the bass control is advanced, it will start motorboating.  Never had a Magnavox motorboat before.   :-[
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 09, 2018, 10:13:09 AM
I'm thinking out loud at the moment.  You guys feel free to jump in here and bail me out.   :)

Referring to the schematic for the 5700 tuner posted in the Downloads section at the top of this page, and referring to the 9300 amp schematic, also posted in Downloads.  The 9300 schematic is from Beitman's 1964 edition.  Note also that my tuner is a 7700 series, with one more 6EU7 than the 5700.  This is as close as I have come to having an accurate schematic for my tuner.  I need to take certain poetic license with this until I can get the right schematic.  The 7700 series tuner is closer to the one used in the Imperial and Concert Grand.

I have a hum that is influenced by the volume control.  We may assume the hum originates at a point ahead of the volume control.  If I were to pull all the tubes in the tuner, ahead of the volume control, shouldn't that kill the hum?  If you look at the amp schematic, pin 2 in the Molex connector goes to the tuner.  Pin 2 is connected to the screen of the output tubes in the amp.  There are 300 volts on the screens, but by the time Pin 2 arrives in the tuner, it has 350 volts.  Where and how does it gain 50 volts?  The amp schematic is a Magnavox drawing and the tuner schematic is a Sams drawing.  Could this be an infamous Sams misprint? The screen voltage is filtered to the output tubes in the amp, so why another 30uf filter cap for the tubes in the tuner?  Assume again, for a moment, that the filter caps in the tuner are leaky, why does the hum stop with the volume control?  What about the two 6EU7's behind the volume control, that receive B+ from those filter caps?  Will this be an exception to the rule of separating whether the hum originates in front of the volume control?  If I unplug the tuner audio input to the amp, there is no hum.  That should clear the amp and power supply of suspicion.  I'm having trouble getting my head around the hum originating in the tuner.  I'll replace all the e-caps and coupling caps as a matter of course.  I'm not certain at this point that they are the cause of the hum.  Stand by.... ;)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on August 09, 2018, 10:26:51 AM
   Hi, Greg, just got back from a week out of town with no vintagehifi connection.   Congratulations on getting the 9300 amp all working and especially on the cool running transformer. I was wondering if one side of the tuner filament winding is grounded for the tuner tubes, and the other filament winding that is elevated to the EL84 cathode bias  with the hum control is for just the 6EU7 ? Or all of the filaments go to the one winding ? 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: SeniorSteve on August 09, 2018, 10:46:10 AM
If I'm reading this correctly, you said that with the volume control all the way down there is no hum.  If that's true, you have just eliminated everything from the volume control through to the output tubes.   Is the hum there on all of the different inputs - AM, FM, Phono, Tape?   I'm saying it this way because it has to be picking up the hum from before the volume control because you can adjust the level.   Are you sure it's hum and not a higher frequency motorboating?  Having a schematic is very helpful, but if you don't let's use logic to see where it's acting up.  Are there audio stages before the volume control?   If there is, pull the tube(s) and see if you get the hum to stop.  This is an easy way to find out what stage of amplification is causing the noise.  Going by your description I'm sure the issue is in the tuner.  Don't forget to underestimate the power of a bad ground on a low level audio cable.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on August 09, 2018, 10:57:52 AM
      Greg, I have noticed some strange Sams Photofact things in the past. First, they seem to give high voltages to the nearest 5 volts only. You will see +155 volts or +170, never 173 or 158 for example. They also take actual measurements on a test unit, which is where they also get their slight circuit differences. They used to mention that in some of their monthly newsletters, especially about getting their readings and wiring info off of an actual unit on the bench. Any voltage below a certain amount is called zero, same for AC voltages and ohm resistor readings. They assume you can't measure low voltages with your Simpson 260 or Heath VTVM. 
           Having that extra 6EU7 tube, does that mean that your schematic agrees more with the dual 12AX7 schematic, except for the tube type. ?  You might have the volume control between a preamp tube and a tone control tube. Do the cathode bypass  caps for the preamp tubes share the same filter unit with the 350 volt filter caps ? If these any leakage in between the 350 volt filter caps and the cathode resistor bypass caps it will inject ripple into the cathode circuits.
  If there was an open ground between the filter can metal and the chassis, that would cause some ripple hum and also motorboating with all the controls advanced full on but it is strange that all the hum goes away with the volume control at minimum.   
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 09, 2018, 11:11:09 AM
I appreciate you guys jumping in here.  I'm going to make this brief.  I want to try something you guys have suggested before I forget what I need to do.  Stand by... :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on August 09, 2018, 11:28:36 AM
               Sorry to butt in while you're trying something, but I have to leave soon for a doctor's appointment. Just noticed on some of the schematics that there are two grounds from amp to tuner in the Molex connector.  One is probably for he six volt tuner filament winding from the power transformer. That wire might be a thick one. The other ground wire, probably connects amp chassis ground to tuner chassis ground, probably filter can metal to filter can metal on the two chassis. If the guy replacing the power transformer somehow has the two grounds connected to each other on the amp chassis, instead of allowing the 6 volt winding its own separate wire, that might cause hum.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: voxACthirtee on August 09, 2018, 11:35:00 AM
I strayed from following the thread for a bit, but (sort of) caught up.
Couple things-
1) If you are really trying to "form" new filter caps you need to do it with a solid state rectifier of some sort  a plug in unit, or something cludged. Tube Rectifiers won't pass DC until the rectifier heaters are getting close to full-ish voltage(or maybe 60+%-ish?) So as you wind up and wait, your tube rectifer is passing NO DC and then it passes a rush of DC at 60-ish% of full. So you've pretty much wasted your time.I build guitar amps, i used to bring them up slow with a ss plug in, but i no longer waste the time. Never had a problem when using a quality cap. Flip it on and GOOOO
2)Post the model # of the Tuner again, at one point i tracked down a 57-xx-xx series tuner that was only on an "addendum" type SAMS. So it had just the 57 schematic and other mixed schematics from other manufacturers. It MAY have been from the Ivory ST Theater i gutted that was in New Jersey but i can't say i know for sure. I'll look for the Sams(hopefully i labelled it). Post the tuner #
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: voxACthirtee on August 09, 2018, 11:36:18 AM
That would probably cause the overall amp to hum, you wouldn't be able to turn it downwith the volume

               Sorry to butt in while you're trying something, but I have to leave soon for a doctor's appointment. Just noticed on some of the schematics that there are two grounds from amp to tuner in the Molex connector.  One is probably for he six volt tuner filament winding from the power transformer. That wire might be a thick one. The other ground wire, probably connects amp chassis ground to tuner chassis ground, probably filter can metal to filter can metal on the two chassis. If the guy replacing the power transformer somehow has the two grounds connected to each other on the amp chassis, instead of allowing the 6 volt winding its own separate wire, that might cause hum.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 09, 2018, 11:58:06 AM
I just got started in the garage, then got interrupted.  I really need to put up a neon "NO GIRLS" sign, I guess.   ;)

I discovered another component in the audio stream I had forgotten to include in my thinking.  The remote control chassis.  Audio goes thru it, between the tuner and the amplifier.  However, if I remove the last 6EU7 from the tuner, the hum goes away.  My next step is to disconnect all the inputs from the tuner.  Phono, MPX adapter and the TV.  See if that makes a difference.  I have the hum on all the inputs that I can try.  I have to leave the TV plugged in or things won't work for some odd reason.  I do not want to power up the TV chassis for any reason until I get it checked out and the damper socket changed.  The comment about the two 6EU7's being on opposite sides of the volume control was one I had not considered.  The hum I have is not the raspy, nasty hum typical of a leaky filter cap.  This is the soft hum you hear if you touch the volume control with your finger.  If the volume control is advanced or if the bass control is advanced, it starts motorboating.  Sounds like somebody who ate three helpings of beans.   ;)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on August 09, 2018, 03:29:30 PM
 Just thought I'd mention that some of the Magnavox tone controls act to blend the bass from both channels. The effect is more pronounced as you go lower in frequency and I'm guessing that at 60 cycles there is total blend of the two channels. So if only one channel had the faulty component or tube, , say from a shorted 6EU7 cathode to filament, both channels would sound equally loud, as if the power supply was at fault. I'm still looking at the downloads, some are in Consoles, some in Tuner-Preamps.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: SeniorSteve on August 09, 2018, 10:10:23 PM
I was looking at the downloads as well trying to see how Magnavox does the volume section by remote.  In both instances I see that there is a volume control motor and the low level signal wires do not go into the remote.  I'm not sure if your remote is different, particularly since it is a stereo theater model.  If anybody would know about the model differences, I know you are on top of it. 

I guess what I'm trying to explain is, if you have a motor on the volume control that adjusts the level, I don't think the audio is routed through the remote chassis.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 09, 2018, 11:03:56 PM
On mine, the black (Ch1) and the green (Ch2) inputs to the amp from the tuner are directly connected to the remote chassis.  The black and the green wires then go from the remote chassis over to the amp.  I can take a patch cord, which I've done, and couple it to the black and green wires from the tuner directly to the amp, bypassing the remote for test.  So, on this particular remote control system, it appears to me that the remote will control the power, volume for both stereo and TV and change at least the TV channels.  The Total Remote Control system on this ST is totally different from the Phantom Control used on the Concert Grand and Imperial models.  And on the 1961 and older Stereo Theaters.  Solid state Total Remote Control was brand, spanking new for the 1962 model year.  I have two complete systems for this instrument.  Two remote transmitters and two remote control chassis.  I have pictures of this setup that will make more sense than my babbling.....

I got interrupted in my troubleshooting, so I need to go back and clean that up a tad.  What I BELIEVE I know is this.  The hum is common to both channels, is between the function switch and the volume control.  The hum appears in any position of the function switch.  Pulling the last 6EU7 kills the hum.  The volume control affects the hum.  So I'd have to say definitely the hum is in the tuner.  I still intend to pull inputs just for grins, but I'm thinking at this point the trouble is in the tuner, per se.  Ed's comment about it "seeming" like it is in both channels when it is in only one and is being transferred to the other channel is well-taken and something I'll check into.  I'm having to study a bit to figure out how to run this situation to "ground."  It's been a while since I had to do something like this, and if you don't do a certain thing every day, your skills get rusty.  I appreciate you guys brainstorming on this.  "Gloriously Complicated"  :)

And, as an aside, so we will be on the same page, there is nothing on this instrument except for the 9300 series amp, on this forum that is completely accurate.  I am using schematics for both the 5700 and the 6100 series tuners so I can get a baseline to try and figure out what I have.  I have factory literature coming for this Stereo Theater.  I just don't have it yet.  I gripe when someone else works on something without a schematic and I'm doing it myself.  Sometimes you just gotta do the best you can....... :-[

Phantom Control use RF signals, sent to an amplifier, to control solenoids and motors for the various functions.  Total Remote Control is an ultra-sound system that used sound to control a solenoid that operates a function switch.  The TRC chassis is in series with the TV chassis and the radio tuner.  TRC controls the instrument without actually changing the settings of anything.  Kind of a strange contraption.  They used it for several years.  There is a little power switch above the TV tuner that turns on power to the remote control.  There is another switch on the rear of the cabinet that turn the remote control on and off.  I'm not cetain yet just how that switch affects things.  Guys, I'm telling you this is the most amazing device I ever worked on.  That so many of these things are being robbed of their amplifiers and trashed is a real shame.  These instrument are marvels of Rube Goldberg engineering.  So incredibly complicated, just for the sake of complication, yet so incredibly simple.  With a couple of exceptions, there acres of room to work.  There is nothing here I have no seen before.  The TV looks pretty simple, not much to it, really.  It may kick my butt trying to fix it, but that will be due to my inexperience, not to its sophistication. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 10, 2018, 12:08:57 AM
I may be done until I get the right schematic.  I have been studying the one for the 5700 tuner, and I find that I'm all wet.  The function switch that sends signal to the 6EU7 is actually behind the volume control in that drawing.  There is nothing between the volume control and the function switch in that circuit.  The only thing ahead of the volume control in that drawing are the various inputs and the front end of the radio.  I'm going to run the test we discussed earlier and get the tuner out of the cabinet so I can see the backside of the chassis.  Maybe I can make some sense of it that way until the factory literature gets here.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: SeniorSteve on August 10, 2018, 09:15:18 AM
I don't know if you had replaced the filters on the tuner itself.  It doesn't take much ripple on the B+ line in an early stage of an audio amp to be amplified in the following stages.  Hope it's something simple like that.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on August 10, 2018, 09:36:37 AM
              Something you might try before the schematic arrives.  With the volume advanced enough to hear the hum without blasting out the speakers, remove the tuner RF and IF  tubes one at a time until they are all out, including the 6AL5. If the hum lowers each time you pull a tube and finally disappears when they are all out, there is some kind of ground loop in the filament connections of the separate 6 volt winding for those tubes. With the Molex connector disconnected and the 9300 amp unplugged from the AC line, there should be infinite ohms between either wire of that filament winding to ground. This isn't the filament winding going to the hum control and the EL84s, its the other one, that has wires direct to the Molex connector and nowhere else.
          I still can't figure out why hum disappears when the volume control is turned down but those 6EU7 grids are maybe picking up 60 cycle hum from something and the fact that you hear the pure sine wave hum and not the raspy power supply ripple buzz almost has to point to the filament winding somewhere. Where does the remote control chassis get its filament voltage from ? 
           You really get the unique problems, Greg !!
         
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 10, 2018, 12:09:50 PM
Steve, I have not recapped yet.  I want to eliminate possibilities while the chassis is still in the cabinet.  This thing will be a royal PITA to power up out of the cabinet.  Recapping is in the plan after the tuner is out of the cabinet.  I do not understand why there are filters on a B+ line that is already filtered. 

Ed, my next procedure is to disconnect all the inputs.  Then I'll pull the tubes in the tuner, one at a time, starting with the 6CY5 FM RF amp.  I was thinking there was a floating ground somewhere, maybe in the volume control itself.  I'm not sure if that would cause motorboating.  I always thought mototboating was a form of oscillation caused by inadequate capacitance.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 10, 2018, 01:52:40 PM
I talked by telephone with a buddy of mine in Phoenix who deals with tube amplifiers.  Higher end stuff than console stereos, but the same technology nonetheless.  His explanation of the pre-amp section of this tuner finally caused the "light to go on".  The "filter" caps in the tuner, the two 30uf@450 jobs, are actually there for plate bypass duty.  They are there to discourage oscillation (hum)!  And he seemed to feel like what I am hearing is not hum, per se, but a type of oscillation heard when leaky plate bypass caps added to an open or drifted grid load resistor is encountered.  EACH 6EU7 has a cathode bypass cap and a cathode bias resistor on EACH triode.  So each 6EU7 has two bypass components on them.  If one bypass is defective, it is quite possible that a hum would be heard in the other triode.  So, we have been on the right track all along.  I will remove the tuner and recap it.  At the same time I'll check all the grid load resistors in the entire tuner, not just in the audio section.  This has to be a simple problem, as it is affected by the volume control.  This may be one of those times where even though the volume control affects the hum, the problem may well be BEHIND the volume control.   :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 10, 2018, 02:36:57 PM
To paraphrase Donna Fargo: "I'm The Happiest Guy in the Whole USA!   :) :) :) :)

I FOUND THE HUM!!!  IT IS GONE!!

You ain't gonna believe this one.  Name a component, any component, the least likely to cause this hum or oscillation or whatever it was.  Congratulations!  You nailed it.  The Multiplex adapter....... :-[

Yep, the Multiplex adapter was the culprit.  I still need to recap and that, but what I found was this.  The excellent suggestion was made to remove all the inputs, just for grins, to see if the problem was internal or external to the tuner.  The input RCA jacks are on the rear apron of the tuner chassis.  The rear apron is on the bottom.  I need a mirror and light to identify the individual inputs.  I had not checked those to see if they were connected properly.  I found that Mr Magnavox technician, the guy who used tape on the PT wires and who used 32 Radio Shack lifetime tubes, also connected the input of the Multiplex adapter to the "Tape In" jacks on the tuner.  I don't know if the tuner has been damaged somehow or if the MPX is wonky.  I have a spare two-tuber I can use to test.  I danced all around this thing.  It was right in front of my face the whole time.   :-[
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Motorola Minion on August 10, 2018, 03:01:39 PM
Greg,  You have an "FM stereo" position on the selector switch in addition to the "tape" , correct?  My 57-03 mag preamp-tuner only has "stereo" inputs for tape or phono.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 10, 2018, 03:09:40 PM
Your tuner has no provision for stereo FM?   I was under the impression that all the stereo tuners had FM stereo provisions, with the use of an MPX adapter.  This tuner has TV, Aux, (tape) AM, FM, FM AFC, FM MPX and Phono selections.  The connections on the chassis will say "Main Sub" and MPX stereo 1 & 2.  The wonkiness with mine appears to be in the MPX. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: SeniorSteve on August 10, 2018, 03:14:14 PM
Great news!  Now you know you have a great start!  I know you weren't going to let it get you frustrated.  I always like good news, especially since you waited what, 3 years for this one.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 10, 2018, 04:55:14 PM
Yep, three years.  This thing is going to be a sweetheart.  It will be worth every second I spend on it, every sleepless night wondering if I'm up to the next challenge.  The hard part is over now.  I have heard it speak.  I know what's causing the hum.  I've heard the sweet sound of a Magnavox 9300 amp doing its thing.   :)

I have the radio tuner out.  I only want to do that once.  I'm going to kluge a way to test it out of the cabinet before it goes back in.  In fairness, the big speaker and the TV tuner should come out to get the radio tuner out.  This amp drives the 12" speakers pretty hard.  I'm going to give serious consideration to installing the pair of 15's that I have.  The Channel 2 horn is not as loud as the Channel 1 horn is.  The crossover networks are original. 

Now some pictures of the week's progress.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 10, 2018, 04:59:08 PM
The tuner is out.  I removed it the hard way.  I'll be smarter going back.   ;)

My 7700 series tuner is a closer relative to a Concert Grand tuner than to the Symphony tuner.  It even has holes for the extra tubes.  Notice the phono balance control is not there like on a CG.  Very similar, though.  This tuner is coded for the 31st week of 1962.  My Stereo Theater must have been made up from leftover parts.  The codes are all over the place, and the cabinet stamp says model 417.  The model number/serial number sticker says model 418.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 11, 2018, 03:31:06 PM
I'm going to remove the big speaker on the tuner end before the tuner goes back in.  I may not be so lucky next time.   ;)

I have the tuner on the bench.  I have the glass dial out so it can be cleaned.  Years of cigarette smoke has built up on the bottom of the glass.  That is not good.  The glass is reverse-painted.  I have never had to deep clean one before.  I'm going to use a damp rag and extreme caution to clean it.  So far so good.  We need to keep a good thought here..... ;)

I'm going to recap the tuner and blow the dust and dirt out with compressed air.  Carefully.  I'll do some cleaning and polishing and put the tube shields back on.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Alfista on August 11, 2018, 04:31:59 PM

  I have the glass dial out so it can be cleaned.  Years of cigarette smoke has built up on the bottom of the glass.  That is not good.  The glass is reverse-painted.  I have never had to deep clean one before.  I'm going to use a damp rag and extreme caution to clean it.  So far so good.  We need to keep a good thought here..... ;)


 These are the details that I hope will be abundant in your thread. Please keep us posted on what technique(s) you choose and how they work for you. Maybe even with pics?

-Tim
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 11, 2018, 04:44:10 PM
Tim, somewhere in the back of my mind, I remembered that Magnavox used real paint on their dials, rather than the delicate stuff used on most tubes.  I did not take before and after pictures, due to the delicacy of the dial and the "fumbleness" of older fingers.  My cleaning was successful.  I used an old dish cloth my wife had discarded.  I wet it to just damp, not dripping with plain water.  I started out on the front, tested the "Magnificent Magnavox" for steadfastness, then went on to the back side of the dial.  That is the side all the white numbers are on.  I started out easily at first, then got more brave as I saw the letters staying on.  I recommend a light hand and not doing any more rubbing than absolutely necessary to get the glass clean.  I would do a section, then wipe with a microfiber cloth.  It turned out really nice.  Would Windex take the printing off?  Don't know.  Don't want to try to be sure, either.   ;)

There are metal tabs bent over to hold the glass in.  It has little cork pads to cushion the glass.  These tabs need to be straightened out to remove the glass.  That procedure works pretty well most times.  Putting the glass back is the trick.  If one gets too aggressive bending the tabs back to hold the glass in, you can break off the corner of the dial, or, worse yet, crack or break the glass.  You need to watch the tabs carefully and listen for crunching glass.  IT is a very delicate procedure, that needs to have caution and lots of patience used.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on August 11, 2018, 08:34:39 PM
Congrats Greg!  I am very happy with your success so far.  Great photos, Bob would be proud.  ;)  It's neat for me to see it apart as I only saw it together with all the dirt and nicotine stains.  :)  It's going to beautiful when done.  I'm also happy that you are sharing your discoveries, procedures, and outcomes.  I think we are all looking forward to your next steps in your "Gloriously Complicated" journey.  Please keep the documentation and photos coming.

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 11, 2018, 09:51:45 PM
Bill, I appreciate your support and kind words.   :)

I have found enough Sylvania tubes in my stash that are more sparkly than the RCA's so I'll put those in the tuner.  I have started my new tube shield polishing procedure I discovered.  I have had problems getting tube shields to look bright and clean.  I found that using stainless steel polishing rouge on my brush grinder wheel, it cleans and polishes tube shields like they were chromed.  I can put all RCA tubes in the TV chassis.  The only Radio Shack tubes I'm going to keep and use are the 6EU7's.  All I have left to do to the tuner is replace the two 30uf@450 caps in the can.  Then I'll blow the tuner off with compressed air and check my work again.  I can test the tuner out of the cabinet.  If all is well, back she goes.  There is a sheet of aluminum under the radio tuner, presumably to shield the TV tuner from the radio tuner.  It needs a good cleaning to get the cigarette scum off. 

I don't see any damage that was done to the tuner when the MPX audio cables were incorrectly installed.  FM stereo worked.  I found an audio cable from the MPX that had tape on the end of it.  Taking resistance measurements revealed a poor ground, and intermittent conntection on that audio cable.  I'm hoping a good set of audio cables from the MPX to tuner will remedy the oscillation and motorboating caused by the floating ground.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on August 12, 2018, 05:16:12 AM
    Congratulations on solving the hum problem, Greg. Is there now another, less serious hum problem on why those cables have a hum voltage on them ?  I think you said they came from the multiplex chassis, or is it the remote chassis ?  Well at any rate it is something you can put off while listening to the now hum-free amplifier pour out the sound  and the picture of the underneath of the 9300 looks nice and clean.
      I am looking at different downloads to try and figure out which chassis of the many in that stereo theatre have power transformers on them and which ones get their power through a wire harness and Molex connectors from another chassis. Magnavox might have left disconnected  some of the RCA phono sockets ground connections in order to avoid ground loops and it might not be shown on the schematic diagrams. Just something to keep in mind when you get to cleaning up the multiplex and remote chassis. Also the TV chassis.
       Good luck and I know you will conquer all !!
         
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 12, 2018, 12:59:39 PM
And moving right along.....

I have the capacitor can on top of the tuner chassis cut apart, the guts removed and two new 33uf@450 volt caps installed.  Working room, in this case, is really tight.  My eyes were playing tricks on me and I had problems getting the ground wire to take solder.  I polished up the tube shields and have some cleaning done on the chassis.  I will install the dial glass and replace the dial lamps.  Easier to do that with the chassis on the bench than in the cabinet.  Some final cleaning, another check of my work and some compressed air blowing out contaminants, and I should be good to test.  I have some pictures as soon as I get them downloaded.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Magnavoxland on August 12, 2018, 10:58:22 PM
Greg, never use Windex or any other harsh cleaner on a glass tuner dial on the side where the lettering is.  The same holds true for lettering on record changers, like speed numbers, etc.  I learned the hard way on this.  I use plain water on tuner dials...nothing else...
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 12, 2018, 11:02:13 PM
My concern on this one was all the cigarette smoke.  I wasn't sure water would cut it.  It seems to have gotten it.  I have never had one that needed more than just a good dusting in the past.  Good point, Larry and always good for a reminder.  Taking those numbers off could have made for a long day...... ;)

Ed, what I believe I'll do now is to kluge up the tuner where it will run out of the cabinet.  Then I need to make sure there is no noise introduced in the FM MPX mode of the function switch with the MPX disconnected.  All being well in that test, then I'll reconnect the MPX with a different set of audio cables and note any difference.  I don't see a reason to believe there is more trouble than that at this point.  The only capacitor in the MPX is a 30uf@450 in the can on the chassis.  I don't believe I'll change this one.  I tested the black audio cable from the MPX to tuner and found a floating ground.  Apparently there is an intermittent in the shield. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Magnavoxland on August 12, 2018, 11:09:39 PM
Sounds like it's been in a home of heavy smokers.  I had one like that, and I put one of those liquid plug-ins right behind the cabinet, put in new refills once a month, and three months later the cabinet smelled a lot better.  The problem is that smoke permeates the wood and gets in the grill cloth, and even the speakers and elsewhere.  It takes a long time to totally get rid of the smell.

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 12, 2018, 11:15:09 PM
Parts of this are not bad, other parts are pretty bad.  The CRT is thick with it.  The amp chassis was as was the MPX.  The tuner, per se, not bad.  The dial glass was the worst of the tuner, really.  I had thought about giving the entire inside of the cabinet a spray coat of shellac.  I'll have it gutted, so that will be a good time to do it.  The wife does not smell any cigarette smoke with the Stereo Theater on the bench in my garage.  I'm concerned that there might be some odor when it gets in the house.  I will be replacing the grille cloth.  Have you had experience of heard of anyone using shellac to seal cigarette odor?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Magnavoxland on August 12, 2018, 11:23:43 PM
Not heard of using shellac for that.  Might be a good time to Google getting rid of smoke odor on wood....
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 13, 2018, 12:02:31 AM
My cabinet does not have a dent on it anywhere.  The finish is not very good.  Something has landed on the flat surfaces on the cabinet and ruined the finish.  Go-Jo on a rag takes off the finish, right down to bare wood, on the flat surfaces.  No idea what caused that, but I suspect a cleaning method of some kind.  Perhaps lacquer thinner.  There are two different types of grille cloth.  I'm sure that is not factory original.  I'm not going to attempt to develop a refinishing plan until I get the cabinet gutted.  I want to make a rotisserie for it, a miniature version of how we did car bodies.  The cabinet will likely weigh more than 100 pounds gutted.  I need a way to move it around and work with it, with a minimum of lifting.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on August 13, 2018, 01:25:08 AM
  Simple Green seems to be designed just for dissolving smoke like that. In 2001 my car burned up in my mothers garage  right next to her car. Her blue Buick LeSabre was coated with a darkish hue on one side. Even straight ammonia didn't completely remove the smoke bu Sinple Green instantly removed it with one swipe.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on August 13, 2018, 01:59:35 AM
     I don't know why Simple Green it works so well, even compared to straight ammonia and Windex-type of cleaners. It smell so mild and isn't at all pungent or a skin irritant like ammonia but one look at the rag after wiping will tell you all. I'm sure it's ok for the cabinet finishes too, even full strength at least if you wet the rag only and don't let the liquid sit on the finish. It didn't affect the finish on the Buick one bit, of course that was a tough acrylic type that had never had rubbing compound on it. Nowhere on the bottle does it say that it is especially good at removing smoke, just that it is a good general purpose cleaner
       Speaking of cigarette smoke...……..years ago I was in a weekly duckpin bowling league at my uncles ancient low ceilinged bowling alley in Dundalk, in blue collar Sparrows Point steel mill area where cars parked outside got an orange coating of steel mill soot on them. All the bowlers seemed to be cigarette smokers but my uncle had these huge air purifiers filtering the air constantly hanging from the low ceiling above the seat areas just behind he foul line and the approaches where they would do the most good. You never smelled cigarette smoke even when half of the cigarettes sat in the ash trays, nor did you see any haze, the machines must have been activated charcoal types.
       Even with all that constant filtering, and even though you never smelled a lit cigarette while bowling, when you got home afterward and pulled your sweater off over your head, you would catch a strong whiff of cigarette smoke as you did the next morning in the shower when you rinsed the shampoo out of your hair.
Not faint and subtle either. The rinsed soapy water going into the shower drain even had a brownish tint to it like the bloody water in the Psycho shower scene with Janet Leigh.
        At Westinghouse we would get these test consoles shipped up from the original plant where they had been stored for years after running constantly with 2 or 3 shifts during heavy production of aircraft radars in the sixties and seventies. When the plastic wrap dust covers were peeled off, we were greeted by a strong tobacco smell, even after years of storage (we tested spare parts made years after production ended) and the Hewlett Packard light grey rack mount test equipment was a medium brown color.
We don't realize what it was like nowadays with no smoking even on the ocean beaches, at least in Maryland.
     
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 13, 2018, 08:55:56 AM
Simple Green could well have turned my Magnavox dial glass to a plain piece of glass.  Although Magnavox reverse painting seems stouter than some, I'd bet it would not withstand rubbing it with Simple Green.  You're right.  Simple Green cleans about anything.  I used it in my pressure washer when I was cleaning an old car up pending restoration activities.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on August 13, 2018, 11:13:49 AM
              Definitely, regarding the glass !!  It seems that no matter what you use on a glass dial, everything under the sun turns into Comet and steel wool once you touch it to all those painted on numbers and letters. When I clean a glass dial nowadays, I use my little finger wrapped around a soft cloth moistened with a small amount of Windex and I will wipe only the large areas of glass (or plastic) that are nowhere near the painted areas
      Then I take a Q-TIP and go closer and closer to the painted areas, still without touching them. Then maybe a final Q-tip rubbing softly over the actual painted on stuff, but only with a bit of plain water, and it scares me to do even that. 
          But even undiluted Simple Green doesn't seem to do anything to varnished or stained wood at least if you have a soft cloth and don't rub hard. Pampers baby wipes also are very good at taking off fingerprint type of grime, like around knobs on front panels and door pulls. If you put a sliver of one between a toothbrush and the fluted part of the knobs, they will soften and remove all the junk that collects on the knobs.  An acid brush with the bristles trimmed very short is good for finely fluted knobs, like on Fisher tuners and preamps from the sixties. I've never tried the Pampers stuff on dial glass because it leaves a smeary  film on it and you have to clean it off with a glass cleaner or plain water anyway.
       A glass dial cleaned up on inside and outside and edge lit with pilot lights is so pretty at night. So are cleaned up tubes when lit viewed from the back. Makes it worth all the effort and time spent with the Q-tips
   
         The markings on vacuum tubes seem to dissolve with anything wet, even plain water. I steer clear of them, trying to get the rest of the tube clean and shiny without getting near the markings. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 13, 2018, 11:41:37 AM
One of those little soft brushes that women use for makeup is excellent for cleaning the dust off your record player needle and for cleaning the markings on tubes without taking them off.  I got a bunch at an auction and use them for everything delicate.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Alfista on August 13, 2018, 02:02:56 PM
  I want to make a rotisserie for it, a miniature version of how we did car bodies.


You know we're going to need pics of THAT, right?
 -Tim
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 13, 2018, 10:38:24 PM
I have it drawn out, but not perfected.  It will have to be made of wood.  The ones for cars are metal.  It will need to be adjustable for multiple cabinets.  I have not come up with a good method of attaching the cabinet to the rotisserie.  It can't attach with screws or bolts, nor can any modification whatsoever to the cabinet be tolerated.  It has got to clamp on somehow.  But to what and to where.  The cabinet bracing is not stout enough.   Maybe where the casters attach, but then it will be top heavy. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on August 13, 2018, 10:49:25 PM
How about just a low bench out of 2x4s and plywood or OSB?  You don't really need much rotation for refinishing.  A simple approach gives more time for actual work.  I did my GE radio cabinet on a Workmate,  bit too high but the cabinet was light enough to flip it around onto its back. 

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 13, 2018, 11:22:11 PM
That's a good suggestion, Chris.  I had considered and rejected a similar idea.  It may be time to revisit that line of thinking.  It will be simpler and still get the job done.  Any suggestions on how high off the ground would be best?  Is 12" too low?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 14, 2018, 12:32:47 PM
I have eliminated the hum from the MPX.  I not only used different audio cables, but I also removed the tube shields from the MPX.  I have done that in the past.  The shields are clean, I sanded the prongs that hold them tight, but I still get motorboating and hum with the tube shields on.  Let's assume for a second that I actually "fixed" it.  I have no idea what I did that "fixed" it.   :-[

The record changer has a bad LP needle, so I used the 78 needle.  This thing has the best sounding record player I own in a Magnavox.  The changer sounds like it is grinding walnuts when it runs, will not drop a record and won't shut off when the record is done, but its audio output sounds fantastic. 

I let this thing run for a couple hours and the PT gets as warm as all the rest of my Magnavox PT's get.  This thing is gonna be a hot performer.  It has excellent radio reception.  The tuning meter has a mind of its own.

I may take a couple days off from this project.  The next thing to tackle is the TV.  I need time to get my mind right.   ;)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 14, 2018, 02:02:02 PM
The tuning meter has a wonky needle.  It appears to be sticking somehow.  If I tap on the dial glass the needle will come up and stays.  When I shut the tuner off, the needle stays where it was until I tap on the dial glass again. 

The changer will need the usual tune up.  Drive tire, motor mounts, an LP needle, some WD-40 and some cussing.  I'm not sure anymore what cartridge it has.  I'm pretty sure it is an Electro-Voice, but the model number is what I'm not sure about. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: SeniorSteve on August 14, 2018, 02:20:44 PM
If it was as smoky as you mentioned, I think your "wonky" tuning meter is from the smoke getting into the meter pivots.  The tar is sticky and settled into them.  To fix, you will have to pull the meter apart and use a q-tip to get some sort of solvent (alcohol works fine) and touch the pivot points with the tip, blow gently to dry and repeat several times.  Once done, I think leaving it dry would be best.  That's how I would tackle that issue, and if the tuner is out of the cabinet, now would be a great time to fix it.  I'm enjoying reading about your progress, keep up the good work.

Steve
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on August 14, 2018, 09:20:15 PM
That's a good suggestion, Chris.  I had considered and rejected a similar idea.  It may be time to revisit that line of thinking.  It will be simpler and still get the job done.  Any suggestions on how high off the ground would be best?  Is 12" too low?

For me, working bent-over is the worst position.  I'll either stand or kneel down.  Years ago I built a little step stool out of scrap lumber and then dressed it up with paint & varnish.  The goal was to get some extra height for lifting the iceboat onto the truck rack.  But then it proved helpful for working on the sailboat in the marina boat barn--sitting on it for low projects, standing for things that didn't really need a ladder.  It's just over a foot high, and has a handle slot cut in the middle of the top.  Must useful tool I ever made.

So maybe your bench could be the right height for standing for most work, and then have a stool of some kind when you need a little more height or for sitting on when you want to be low.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 14, 2018, 10:45:28 PM
Steve, unfortunately, the tuner is back in the cabinet.  I had not considered the possibility that cigarette scum would mess up a tuning meter.  Makes sense now I think about it.  The tuner has to come out again to refinish the cabinet.  I'll note your suggestion on my "to do" list.  Thanks for that suggestion.  That'll probably be the cure, and it certainly can't hurt. 

Chris, my workbench is 32" high.  That will be too high for me to spray without standing on something.  Bending is not a problem for me.  Working too high is.  I'll do some experimenting and see if I can come up with a height that will work.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 14, 2018, 11:04:55 PM
Time for some pictures.  The last picture, the one I worked hardest to get is fuzzy.  I ask your indulgence, and pray your forgiveness.  My eye surgery plays tricks on me occasionally.  I passed on the good shot and took the fuzzy one.

This will show my re-stuff methods on the plate by-pass caps on the tuner chassis.

You will notice in the first picture a bubble in the felt backing on the dial.  This bubble apparently has been there since the tuner was built.  I used my Exacto knife to cut a slit in the bubble.  Then I used a tooth pick with glue on it to dab some glue behind the bubble.  I pushed the bubble down and weighted it overnight with a bottle of speaker cement.  It is hard to get glue behind the bubble using a toothpick, but about 90% of the bubble is gone, good enough for a "cheap labor' job.  You can see in the last, (fuzzy) picture that the bubble is not noticeable and that the dial glass came out pretty good.  You need to be careful putting the tuner back into the cabinet.  The amount of tightness of the bolts determines the alignment of the knob holes and how much tension you put on the plastic bezel.  My bezel was cracked when I got it, so I had to be extra careful.  Nichicon PZ caps are actually better for restuffing, since their bodies are thin.  This worked okay since there are only two caps in the can.  Working under than can is the tightest place anywhere on a Magnavox stereo.  Fortunately, one only has to do that once per instrument.

I resealed the can with chrome HVAC tape. 

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 14, 2018, 11:30:32 PM
I cut the capacitor can in two with my Dremel tool.  I made a mark radially and vertically.  The radial mark is to keep my sawing somewhat straight and the vertical mark is to "clock" the can so it will go back together somewhat straight. 

I can only post six pics at once, so I have to make another post.  The 6EU7's in this tuner each have their own cathode bias resistors for each triode section.  The first 6EU7 used electrolytic bypass caps.  The second 6EU7 uses common coupling caps for bypass caps, .47 @ 200 volts.  The caps I used for the first 6EU7 are originally 20uf@25 volts.  I replaced those with 47uf@50 volts, the same value I used for cathode bypass in the amp.  I like to increase both capacitance and voltage in capacitors used in bypass duty in Magnavox amplifiers.  I won't go into theory at this point, but if you go too large you run into diminishing return.  I have found that 47uf is about all I need to go.  The theory is that larger caps than stock enhance bass response.  A 9300 series amp does not need help in that regard, but this value is what I had on hand and what I use in everything else Magnavox I've done.

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on August 15, 2018, 07:03:29 AM
Looks good Greg, and I'll bet it sounds great.  :)

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 15, 2018, 08:37:44 AM
It sounds pretty good at this point.  The treble is not as bright as I think it should be and one horn is weaker than the other.  I have not done anything with the crossover caps yet.  I'll have to get some non-polarized caps for it.  Kluging up my own will look too messy for this particular setup.

What I need to know now is how to proceed with digging into the TV chassis without a schematic.  Sams does not print service literature for this chassis, apparently.  Nobody else does that I can find.  Magnavox factory literature is my only hope.  My supply in that regard has been delayed due to health reasons.  I have a couple of obvious things I can do, but I'm done unless someone has an idea how to proceed.  I have read that you should test the CRT (done) then check resistance from somewhere to somewhere else that checks the health of the flyback transformer.  Any TV guys on here who would care to jump in here and bail me out would be most appreciated.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 15, 2018, 03:14:02 PM
I found a YouTube video that featured a Stereo Theater like mine.  It has the five-knob tuner and no remote control.  Interesting video.

https://www.youtube.com/watch?v=Ewh6V-lsK0Q

Maybe this would be a 417?

This video may have given me a clue about the capacitors in my TV.  This video says they are mylar, the good kind.  So maybe fix the damper tube socket, clean well, test small tubes, replace the filter caps and ramp up voltage slowly.  Then make repairs as needed.  I have seen three videos now where they just plug it in and turn it on.  Nothing bad happened in all three videos. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 17, 2018, 08:21:46 PM
Jack "Pan Am" asked about the speaker wiring in his Stereo Theater.  He asked for certain information specifically pertaining to how the speakers were wired side to side.

It would be unfair to Jack or anyone else if I took a picture of the wiring diagram in my Stereo Theater ( or other stereo, for that matter) and provided that as documentation for his instrument.  Truth is, although the wire colors are much the same, the individual instruments may be wired entirely different, side to side.  It depends on the orientation of the amplifier and the external speaker switch.  And whether it has a three-position or a five-position external speaker switch.  And whether it has small cone speakers or horns.  The crossover networks in a Stereo Theater are in a different location than on stereos.  And my Stereo Theater has remote control.  The speaker wires run thru the remote on mine.  So my diagram would only serve to further confuse the situation.

Basically the wiring is done the same way in all Magnavox stereo console instruments, bi-amps excepted.  The speaker wires come out of the amp, go to the external speaker switch, change colors, then go to the individual speakers and the external speaker terminals on the rear of the cabinet.  It will help to have the wires clean so you can tell the difference between black wires and brown wires, and blue wires and gray wires.  Dirt tends to muddy the waters when it comes to running down a wiring problem. 

The speaker wires will come out of the amp from a terminal located behind the output transformers.  The orange wire will be Channel 1, the brown wire will be Channel 2 and the black wire will be negative (or common in Magnavox-speak).  The orange wire will be closest to the power transformer, then brown, then black.  These wires end up at the external speaker switch, where they change colors.  Blue and Gray for  Channel 2 and green and brown for Channel 1.  There may be double terminals on the big speakers to use for junctions.  So there would be two black wires on Channel 2 with a blue wire going to the other side and a gray wire going from the same terminal as the blue wire, going to the positive side of the horn.  The black wire from the big speaker then goes to the common terminal on the horn.  Similar on the other side, only brown is on the common terminals, green on the positive on the big speaker, then black and gray to the common and positive terminals on the horn.  Small cone speakers will be wired like the horns, only there will be more connections and the crossover networks are typically mounted somewhere close to the small cone speakers.  The wiring orientation on the small speakers is obvious when you look at it. 

From a practical standpoint, you can pretty much ignore the external speaker switch when you suspect a miswire.  The wires are soldered to it.  Your problem will most likely be on an individual big speaker, at the amp, or on an external speaker terminal on the cabinet back.  These can get bumped and can fall off fairly easily.  It is well to use a pair of needle nose pliers and crimp the terminals a tad so they fit snugly.  If your instrument has horns, they are suspect for losing their wires.  The small speakers, not so much due to their orientation in the cabinet.

I hope this helps more than confuses.  There should be a diagram pasted somewhere in the interior of the cabinet.  This is your surest bet for the orientation of the speaker wires in your specific instrument.  Good luck.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: PanAm on August 18, 2018, 01:13:10 PM
Thanks so much! I am out of town right now so I will be sure to take a look when I get back.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 18, 2018, 04:20:42 PM
Jack, here are the pictures of the external speaker wiring on the back of my Stereo Theater.  I also managed to get a pretty good shot of my speaker wiring diagram.   :)

Even if your instrument does not have the plastic terminal blocks like this, the wiring will be the same.  The "Ch 2" at the bottom is so you an use the console speakers as one channel and both external speakers as the other channel.  I have not tried this, but I understand that it sounds impressive.  I wanted to try it using my Concert Grand as one channel and my Imperial as the other.   ;)

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 21, 2018, 10:53:16 AM
The search for service literature continues.  My Stereo Theater does not exist.  You guys who have one of these need to be on the hunt for service literature if you intend to restore them.  The components in a Stereo Theater are the same, yet different, from "regular" production jobs.  Sams tells me there is no literature for my instrument.  I find that hard to believe.  I'm doing something wrong.  Wrong numbers.  Wrong year.  I'm sure the chassis used in a stand-alone TV would be similar to the one in the ST.  I need chassis numbers to find out.  This is a "Catch-22" situation.  If anyone has a clue as to where to start looking, I'd sure be proud to know it. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 21, 2018, 02:33:38 PM
I made a little progress today.   :)

First thing I did right was to eliminate the hum in the MPX.  I replaced the 30uf@350 plate bypass cap with a 33uf@450 volt cap.  I also replaced the 4uf@50 volt electrolytic coupling cap in the audio output of the MPX.  I cleaned the gain control and the balance control.  Then I replaced all three tubes.  This thing is dead silent as far as power supply hum goes.  I can turn the volume up full with no signal and all I get is a little hiss, like a solid state amp does.  I have excellent sensitivity and selectivity from the tuner.  The audio output is incredible, just what I would expect of a Magnavox 93 Series amplifier.

I also made some headway trying to find acceptable service literature for the TV in my ST.  Outside of factory documentation, I have found no literature available for this specific chassis.  I spoke by phone for the third time with Steve Johnson and we came up with Sams #591, folder 2 for the closest match to what I have.  It is not 100% correct, but close enough and better than what I have.  I'll wait for this folder to arrive and decide from that point how to proceed.  I'm about ready to call this thing a "picture radio" and proceed like I would with an old radio. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Alfista on August 21, 2018, 03:11:24 PM
That's encouraging, makes me want to listen! And helpful to those of us who will be following in your footsteps.

The TV-only chassis is likely to have the audio amp integrated. I have the skeleton of a big ~1968 Magnavox console TV, and the audio was not on a separate chassis in that model.


-Tim
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 21, 2018, 03:31:03 PM
1968 models are different, I'm sure.  I would say the 1961 to the 1963 black and white models with the vertical chassis are all going to be about the same.  Some models employed multiple speakers and featured stereo audio connections.   There is a spot on the audio PCB for a 6AV6 audio tube.  This tube is used when the chassis is used in a stand alone TV.  The audio amplifier and power supply would have been in a chassis in the bottom of the cabinet, under the main TV chassis.

If you decide to restore a Magnavox Stereo Theater, be prepared to drive blind much of the time.  Unless you are extremely fortunate, you will have to punt when it comes to service literature.  Not impossible, just nerve wracking. 

I'll wager that RCA or Zenith does not suffer from the dearth of information like Magnavox does.   ;)

I would hate to swear on a stack of Bibles that I know the ONE spot where the hum was coming from.  I know it was coming from the MPX, but was that the only place?  I did not do anything I would not have done as part of an ordinary tune up.  The difference this time was that I actually fixed something doing my tune up. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on August 21, 2018, 07:31:25 PM
The important thing, it fixed the stereo.  Now you can enjoy and listen without a hum.  :)

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 21, 2018, 10:49:06 PM
I have never had a "hummy" Multiplex adapter before.  The more I did to eliminate the hum in the ST, it still hummed.  I will never know if I had more than one source of hum or if the MPX was it all along.  And, like you said, it really doesn't matter.  We got it, it's gone and we are making progress.  I need to get some non-polarized caps for the crossover networks and order some 1000 volt orange drops for the TV chassis.  The changer works so well I believe I'll leave it until after the cabinet is done.  The very last thing.  I might sand the drive tire to knock down the rumble a tad, though.   ;)

One more example of my infamous "WD-40 changer overhaul" working its miracle.   ;)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 23, 2018, 12:13:17 PM
While waiting on more detailed service information to arrive, I have been looking at the TV chassis.  I have identified at least one tube socket on the 6CG5 audio tube that has bad soldering.  I have read a post on another forum where a member has replaced every resistor and every capacitor that was not ceramic on a Philco Predicta chassis.  I initially believed this to be radical overkill, but, on looking more closely, I see the wisdom in doing that.  I'm considering doing that on this Magnavox chassis.  The Predicta restorer has found over 50% of the resistors in that chassis drifted out of tolerance.  The Magnavox chassis consists of four main PCB's.  Audio, IF and video, vertical, and horizontal and high voltage.  The chassis unplugs from other components and is probably one of the easiest to access and work with you'll find.  Since I am learning about TV repair, going thru this chassis component by component would be a good way to learn.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Motorola Minion on August 23, 2018, 02:56:40 PM
Greg,  Some of the VK artisans do not want anything left to chance, especially on rare models and those that can bring real money. I have been on there for 7 years and prefer to assist the timid and learn from the bold. For those of us with limited bench time and more pedestrian TV models, I do full-recapping with a few exceptions like leaving ceramic bypass caps alone, etc. TVs have so many resistors, its often easier to recap then power up and measure DC voltages on the tubes to sniff out any bad resistors.

My concern always begins with the AC plug, so I install safety caps from both sides of AC line to chassis, add a fuse (1.5 to 2 times steady amp draw) and surge limiting thermistor to reduce tube filament inrush, finishing with a new grounded AC cord. The way some of those tiny AC plugs look with the green ooze around the prongs and cord, I cannot take chances. If I see it, I have to deal with it.

A TV this age needs every electrolytic capacitor replaced, though some VK'ers have had success "reforming" them with gradual power-up and prolonged burn-in. Electro. is all caps 1 uf and higher. Anything from .001 uf up to .47 uf are probably wax-paper and must also be replaced. I do not stuff cans, just disconnect and leave them be. The replacements are much smaller and will be out of sight under (or behind) that chassis anyway. The Magnavox PC boards are pretty rugged but use a 40 watt or smaller soldering pencil and solder wick if you do not have a solder-sucker of some kind.

Based on what I read HERE, I was picky restoring the 93 series amp and 57 preamp-tuner on my '62 Normandy Symphony. I just have not put it together though its already in my attic-lounge, waiting for the room to be done. Resistors drifted beyond 10% were replaced, all the paper and electro caps and I decided a few ceramic disc coupling caps would be better off as mylar. Ceramics being temperature and vibration sensitive, have no place where frequency response could be affected.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 23, 2018, 03:26:37 PM
I'm trying to avoid the "recap then power up and see what happens" scenario.  I only want to fool with high voltage a minimum of times.  I mentioned the restoration done on the Predicta not as a criticism, but as an example of what my thinking was on my Magnavox.  I do not want to charge and discharge a CRT.  Not even once, if I can avoid it.  I want to replace caps and resistors and whatever else may be needed so I can power up once and maybe make minor adjustments, like I do on a radio.  The thought of messing with discharging that CRT keeps me up at night. 

I appreciate your help with this and for being patient enough to coach me thru the process.  I can see where I might get in to TV repair, once I get my head around discharging the CRT.  I have watched YouTube videos and it looks so easy.  I did not like getting zapped by automobile ignition and I learned what to stay away from.  It is difficult to repair something if I'm afraid of it.  I am petrified of high voltage.   :-[

I routinely replace all the components you mention on your Symphony project.  The 220K ohm grid resistors are another component notorious for drifting high.  I replace the cathode bypass capacitor and the cathode bias resistor like I would any other cap in that amp.  There is a double 20uf@25 volt cathode bypass cap on the 6EU7 in the tuner and the double 30uf@350 volt plate bypass cap that need replaced in the tuner.  There are a couple paper caps hidden under the shield on the FM tuner that I replace.  If those tuners do not have AFC, I like to replace the 6EA8 in the tuner with a 6GH8A.  That helps with FM drift.  I check every resistor.  Magnavox did not use the best resistors I have encountered.  They are prone to drift high.  My opinion is you did not get carried away.  I have been accused of "overthinking" this project, but I want to do it right.  The first and only time.   ;)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 29, 2018, 11:31:58 AM
Dave was good enough to send me a Sams file for the TV chassis in my Stereo Theater.  Sams #591, folder 2.  I believe it to be a dead wringer for the chassis in my ST, minus the features that are exclusive to a Stereo Theater.  Case in point is the audio output transformer in the upper left part of the chassis shown in the print.  My chassis does not have that transformer, due to the fact that the stereo provides the audio for my TV.  The folder shows an alternative audio board, which is like the one I have.  The 6GC5 audio output tube becomes a cathode follower in my chassis.  The extra 6EU7 in the radio tuner does audio duty.  Where the output transformer is located in the print is where the amp plugs in and where the audio output cable for the TV chassis is located.  The two setups are really not that much different.  I believe this will work for any Stereo Theater with a 36 series TV chassis, regardless of tuner or remote control setup.  Next, we need a print for the 77 series tuner.  That will answer lots of questions about the remote.

I appreciate Dave taking the time to copy the print and send it to me.   :)

If anyone else has anything on this Stereo Theater, I would appreciate knowing about it.  It does not matter if it seems redundant.  Sometimes there are revisions or additions from one print to the other than can help someone, if not me in this project.  We need to accumulate all we can find on not only my Stereo Theater, but for any Stereo Theater.  We can compile the information and it will help someone down the line when they work on one.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Motorola Minion on August 29, 2018, 03:00:45 PM
Greg,  I'm pretty sure I can find the 77 series tuner schematic to downloads. My 1962 1ST659 has a 79 tuner which sure looks different.

I was not about to upload a TV schematic to the site, though the Early Television Foundation Museum is happy to accept anything I scan, as long as its a TV. ::)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 29, 2018, 10:39:02 PM
Is the 79 series tuner a five knobber?

Having a drawing for the 77 series tuner and knowing its relationship to the remote control would be a god-send at this point, Dave.  Thank you for your help with all this.  I have the tuner sorted, but the remote control is a mystery to me at this point.

I agree that downloading a TV schematic is not something I'd want to do.  My suggestion would be to send whomever needs one like you did to me.  I believe the Sams 591 will work for almost any black and white TV found in a Stereo Theater.  I won't swear to the very earliest 1959 models being the same.  The ones I know of on this forum would likely be served by Sams 591.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 29, 2018, 11:18:07 PM
I received several downloads Paul sent me on how the 36 series TV chassis is supposed to work and how to diagnose problems.  Also detailed information on how the remote control system works and how to diagnose problems with it.  The files are pretty good sized, and contain the Mother Lode of information on these systems. 

Thank you, Paul for your kind consideration in helping us figure these things out.  I appreciate your taking the time to send me this documentation.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on August 30, 2018, 05:00:37 PM
The farther we get from the time when these things were new, the more important it is that service and design info is preserved and distributed so it's saved in multiple places.  It's a great service to the future when people make the information available.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 02, 2018, 11:04:40 AM
When a person gets heavily involved with anything Magnavox, accumulating information is part of the challenge. 

I have also recently learned another tidbit that might be well to share.  A local person brought me his "tube stereo" (Magnavox Astro-Sonic) for me to "work on and get it running."  I don't do that for other people and told him so.  During our visit, I noticed that the knob on one of the sliding lids had broken out of the lid.  Apparently the lid slid open sometime during transport hard enough to break the knob out of the tempered Masonite lid.  Jamming the doors shut with a hunk of Styrofoam then wrapping the cabinet in a blanket and shrink wrapping the whole thing would prevent such a tragedy.  The plastic clips on the front sliding doors on Magnavox instruments is made of unobtanium.  I had transported several Magnavox instruments and never considered damage from the doors moving during transport.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 15, 2018, 12:21:25 PM
I have been working in the garage, cleaning up a bit (okay, a LOT!) before winter.  Fall cleaning, if you will.   ;)

I have a stack of yard sale records that I play both to test changers and to play on instruments with styli of unknown condition.  I don't care if they get ruined.  I have album "Aloha Moods" by the Longines Symphonette Society, on RCA Special Products label.  Although no artist if given for the music on this record "artists of known reputation" can be easily identified on this album as being Lawrence Welk and his orchestra.  Clearly this is the case.  No other orchestra played Hawaiian music with a harpsichord and an accordion.  The background vocals are the Glee Club.  Norma Zimmer's soprano and Jim Robert's baritone are unmistakable.  This record gets processed to digital before it gets ruined.  The fidelity and stereo separation are remarkable.  But I digress.....

I learned one other notable fact this morning.  The boys and girls at Magnavox may have known what they were doing using 12" speakers in this Stereo Theater.  I have threatened, from the beginning of this project, to replace the 12's with a set of 15's I have.  Now I'm not so sure about the soundness of that choice.  This thing still needs the crossover networks rebuilt, but it sounds pretty good now.  The poor old changer grinds and rumbles from years of neglect, but it works absolutely perfectly.  It changes records, drops the tone arm in the correct spot every time and shuts off when the last record has played.  The drive tire has to be rock hard.  I'll go through it like I do the others, but one hates to fool with something that works so well.  Even in less than ideal condition, this old ST sounds ALMOST as good as my Symphony.  That is a high bar in my book.   :)

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 17, 2018, 02:23:25 PM
I pulled the TV chassis this morning.  Really not all that bad as far as dirt goes.  Lots of nicotine on the picture tube.  I have identified at least two trouble spots on the chassis.  There are several broken tube pin connections to the PCB around the 6GC5 cathode follower tube.  This tube powers both the audio and video.  And the burned tube socket on the damper tube.  Methinks this TV was on the blink when the stereo was mothballed.

I see Magnavox continues their "modular" concepts on the way the picture tube is mounted into the cabinet.  One can either remove the brackets from the CRT, you can remove the brackets and CRT from off the wooden crossmember, or you can remove the crossmember with the brackets and the CRT all in one chunk.  Removing the chassis requires disconnecting wiring and removing five bolts.  Piece of cake.  Now if I can just get it repaired properly so it stands a chance of actually working....... :-[
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on September 17, 2018, 08:36:17 PM
So that's what it looks like out of the cabinet.  :)  A little scrub a dub, dub, and I will look like new. 

Bill

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 17, 2018, 10:54:28 PM
I'm planning on using 91% rubbing alcohol on it to clean.  I'm not brave enough yet to put it in the car wash like the TV experts do.  Alcohol allegedly cleans well and will not remove markings on the chassis.  The plan is to print a copy of the resistance chart and run the resistance on the chassis.  Then I can print another copy and make measurements as I replace the old components.  This will let me know early should a mistake occur.  I can fix it before I get too far along.  I have some questions on the best caps to use in the high voltage.  I plan on using orange drop caps to replace those white Goodall caps on the high voltage board.  I want to replace 1/2 watt resistors with one watt, one watt resistors with two watt.  Replace up to 600 voltcaps with 1000 volt and 1000 and 1400 volt with 1600.  Hey, if this plan works on a Predicta, it should work on a Magnavox.   :)

Bill, you can probably get in on some of this in the winter time in AZ if you'd like.   ;)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on September 18, 2018, 07:08:33 AM
So you did decide to take the ST, TV to AZ.  :)  If I come over I can watch and learn.  I need the learning part.

Bill

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 18, 2018, 08:54:11 AM
In the fourth picture I posted above, there is an RF choke that comes off the damper socket.  The choke looks "breakdownable" to me.  Wonder if it is still okay?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Motorola Minion on September 18, 2018, 02:17:28 PM
Probably OK, and you don't want to try finding the exact inductance value online. Just be careful cleaning around any coils. Those are not easy to repair, so use a long-bristle 1" wide paint brush to get all the dust off.

I remember opening old TVs to see dust much worse than that, mostly from houses too near a road, farm field, or with the heat register near the TV on a forced air system. There were literally several-inch long icicles of dust hanging off the CRT leads in one set.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 18, 2018, 03:23:05 PM
That coil is called an RF coil on the schematic.  What purpose does it serve?

How would I test it to make sure it is good?  There are no specifications given for it on the parts list.  Just check for continuity?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on October 24, 2018, 07:27:35 PM
As i mentioned previously, my intention is to do a component level restoration on my TV chassis.  This means to replace all the resistors, all the capacitors except ceramics and replace all the tubes with NOS RCA tubes.  The jury is still out on the CRT.  I plan to clean the tuner when I get the TV chassis done.  Really the only channel that needs to work dependably is Channel 3, so I'm not going very deep into the tuner. 


The guys who work on TV's regularly advocate the replacement of one or two components, then powering up to see if a mistake has been made.  This seems like a lot of extra work and even a good way for ol' fumble fingers me to mess something up, connecting and disconnecting things several times.  This is a printed circuit chassis.  I don't see how I can make a wiring error, replacing one component at a time on a PC chassis.  So my plan is to divide the chassis up into five parts, LV power supply, HV power supply, sweep, IF, and audio.  I will get the parts for a section at a time so as not to have a pile of parts and increase chances for confusion.  I will start a chart as I work.  I want to take resistance measurements and note them on the chart.  Then remove each component, measure it, note its position in the chassis, then do the same for the replacement component.  Then, when I get done and I power up, if I have an issue, I'll at least know what I had when I started, what I did, and won't leave anything to memory.  This chassis should either work perfectly on power up, or it will never work properly at all.  It will essentially be a brand new 1962 Magnavox TV chassis. 


I'm reseaching the RF chokes in the HV power supply.  Makes no sense at this point.


You may remember that, when I was researching codes, we found the MPX adapter with a "253" date code.  There are not 53 weeks in a year, so the code made no sense.  I have since discovered that some date codes were changed to reflect the month they were built, not just by the week they were built.  So, apparently, if one encounters a date code with "too many weeks" this method of dating by month should be considered.  Basically, the date code on the MPX is December ("53) of 1962 ("2").  This lends credibility to my theory that my Stereo Theater started its life as a model 417.  The basic difference between the 417 and the 418 is remote control.  The amp and speakers are dated July 1962, while the tuner, MPX, remote chassis and CRT are dated December 1962.  The 417 code is printed under the amp chassis.  Five knob tuners are used in the 417, while a six-knob tuner is used in the 418 in 1962.  Strange and confusing.  Typical late tube Magnavox practice.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on October 24, 2018, 07:57:59 PM
OK, I'm buffaloed.  How does "53" relate to December? 

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on October 24, 2018, 10:50:27 PM
I'm not sure I understand all I know about it, but there are codes that indicate the month an item was built, versus the weekly codes more commonly used.  I'm further not certain that each manufacturer adhered to a common code.  They may have modified them for their own personal use.  My understanding is that when you get a date code that is greater than the number of weeks in a year, the monthly codes may be considered.  I asked someone who is more knowledgeable about date codes than I am about the MPX in my ST having a "53rd week" date code.  I was informed about the monthly codes and was informed that "253" would have been December, 1962.  Again, research on this continues.  I want to find the codes for the 12 months so this makes more sense.  This is one of those subjects that presents itself as a part of restoration.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on November 05, 2018, 06:02:23 PM
I have the TV chassis set up on a card table in my den.  I have my VTVM and a little cheapo VOM at the ready for resistance measurements.  I have printed the resistance chart given in the repair documents for reference.  I can make notes and whatever else I need to for documentation without defacing the original documents.  I have started measuring resistances in the LV power supply.  I have a chart that I will note resistance readings on to be compared with what they should be.  I will highlight any major discrepencies from spec with my yellow highlight marker.  I will make a chart for each section of the chassis: LV, sound, IF, sweep, and HV.  I will replace components one section at a time.  So far, I have found bad socket connections on the PCB on the 6GC5, a bad damper socket.  I'm not done with the LV power supply section yet, although I haven't found anything that stands out as being amiss there at this point.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on November 06, 2018, 05:59:30 PM
Sounds like you have a good start Greg, and are doing everything you can to make this a working TV.  :)  I know I will be interested with your progress, and I'm sure there are others on the forum. 

Bill

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on November 06, 2018, 06:29:04 PM
I enjoy reading these updates.  They give a bit of vicarious fun to those of us who don;t have time (or knowledge, for that matter) for a such a big undertaking.  I've got a 1951 Crosley that will be a someday project.

Let's see if the image attaches.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on November 06, 2018, 06:33:53 PM
Trying again on the Crosley image.  Can't make it work.  Here's a link:

http://www.tvhistory.tv/1951-Crosley-S11459MU.JPG

Chris
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on November 06, 2018, 09:48:41 PM
I'm still trying to figure out what the RF chokes in the HV power supply are supposed to do, how to troubleshoot them, how to check them, etc.  I need to know more about them than I do now so I'll know how to handle them.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on November 11, 2018, 03:57:27 PM
I also need to Google "quadrature coil".  Sounds mysterious.  This particular series of chassis, the 36 series, is said to have a bug in the audio, an intermittent bug no less, caused by and connected to said quadrature coil.  I need to find it, then figure out how to test it.   :-[


I have decided, out of respect for the quadrature coil and a couple other components I have no idea about, I'm going to start replacing parts in the HV section.  I recognize more parts there.  Common old caps and resistors.  And I need to replace the damper socket, so this decision was logical.  I sure hope I'm not doing more harm than good.  Everybody reading this knows more about this TV chassis than I do.  I've been doing LOTS of reading. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on November 11, 2018, 04:04:06 PM
It's the coil used in the detector, isn't it?  It's a method of FM demod.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on November 12, 2018, 05:36:28 AM
I think the RF choke going to the damper tube socket is there to "clean up" the heavy voltage and current spikes that are generated by the horizontal output tube which is basically a class C power amp circuit like in an AM transmitter but without a tuned circuit in the plate circuit. I don't know if it increases the efficiency of the circuit, if it keeps interference out of the power supply, or the tuner or a combination of the above. The same kind of choke is used to isolate the tuned circuit RF currents from getting back into the power supply in AM transmitters. The "scramble" coil winding and the multiple stacks gives it a high RF impedance over a wide frequency range to eliminate spurious "suck out" resonances. If it looks overheated, a circuit problem is causing it to absorb an oscillation that it was supposed to prevent from occurring. It doesn't look overheated in the picture.
    Not sure how to measure it except for DC resistance. Its one of the "do not measure"
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on November 12, 2018, 06:16:17 AM
     the "do not measure" warnings on a TV schematic include the horizontal output tubes plate cap, the damper tube cathode and some of the horizontal deflection coil wires. Just touching voltmeter leads or a scope probe to them affects the circuit operation. The vertical output tube plate circuit is also a "do not measure".
      The quadrature coil is in a tuned circuit that goes to a special grid in a quadrature detector circuit. Sometimes its called a "locked oscillator" detector. The tube is its own limiter stage and also the FM detector. Its supposed to be so sensitive that it gets noise free audio when the signal is too weak to look like anything but snow on the CRT.
The special grid in the tube gets a 4.5 MHz sine wave voltage on it without being connected to anything other than the tuned circuit "quadrature" coil and a capacitor in parallel. I think just the interelectrode capacitance of the tube electrodes supplies enough coupling to generate the RF voltage on the coil. the voltage is 90 degrees out of phase with the FM signal applied to the normal control grid because the current through the interelectrode capacitance is 90 degrees apart from the voltage. It takes the place of the coupling capacitor from primary to secondary windings in an FM discriminator or the third coupling coil in a ratio detector. The secondary tuned circuit goes above and below 90 degree phase difference with the primary and the diode AM detectors convert the amplitude differences into rectified audio.
       I think
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on November 12, 2018, 06:47:07 AM
   I don't think I've ever seen an alignment procedure using an FM generator and scope for this circuit. The tuning is thrown off even with short low C leads. They usually have you insert an RF attenuator between the tv signal antenna and the tuner input, and weaken the signal until the sound is noisy or distorted then adjust the quadrature coil for least noise or distortion. weaken the signal more,  then readjust the coil tuning and keep repeating until no improvement is possible. Then restore a strong signal with lots of detail, like small lettering on the screen and readjust slightly to null out any buzz noise. That's what the photofacts usually say.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on November 12, 2018, 10:38:02 AM
The quadrature coil sounds like one of those doodads I'll leave alone until I have a reason to mess with it.  Thank you both for the detailed explanation.  That makes more sense to me now.  The quadrature coil is a "TV guy" way of describing the FM detector I would be more familiar with in a radio.  The RF coils do not appear to be burnt.  I did not know what their purpose was, so thank you, again, for that explanation as well.  The only burnt item I see is the damper socket.  Knowing Magnavox tube sockets, I suspect a bad connection started that trouble and it went undetected and untreated.  I'll replace that socket with a ceramic one, which should take care of it.  The HV section contains the typical Magnavox complement of Goodall capacitors, which are immediately suspect in my book. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on November 12, 2018, 12:55:34 PM
I hit my first snag.  I'm having trouble finding an .056 orange drop cap, perferably 1000 volt.  I have been advised not to use the yellow caps like used in radios in TV chassis HV section.  There is a Goodall cap there now.  AES is not going to have everything I need.  AES has quit carrying several of the values of capacitors used in radio and TV sets.  They do guitar amp stuff.  Too bad, they are close.  I may have to rethink my methodology...... :-[


Some guys say not to use yellow caps in a TV, some guys say it's just fine.  This is one of those times I wish I knew what I was doing.  I'll take a more Christian attitude toward newbies after this little experience.   :-[
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on November 12, 2018, 06:26:08 PM

 I'll take a more Christian attitude toward newbies after this little experience.   :-[

I'm grinning.  My Alabama grandmother--Granny, to distinguish her from the Michigan GM, who was Grandma--was a staunch Southern Baptist.  When a child was engaged in something a bit devilish, Granny would say "Now, is that the Christian thing to say/do?"  But the cool part was that she often enough had a twinkle in her eye, as if to say "I'd probably say/do it too." 

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on November 12, 2018, 07:32:58 PM
I have been fooling with radios and stuff like that for well over 40 years.  I get stuck once in awhile, but I muddle thru eventually.  I feel like a total idiot working with this TV chassis.  It has been a long time since I have had that feeling, and I'm not sure I like it.  I don't always give that consideration as much as I should to someone just starting out working with something I'm more familiar with.  I fail to walk in their mocassins like I should.  I'll try in the future to be more tolerant of their fumbling and asking the same questions a dozen times.  I appreciate everyone helping me with this. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: danrclem on November 12, 2018, 10:56:27 PM
If you're looking for Vishay Sprague specific orange drops it looks like they may not come in 1000v.  According to this pdf the highest voltage for a .056 uf is 800v.  They could possibly be make them in another series with the higher voltage though.  Panasonic makes some very high voltage caps but they're probably not what you're looking for. 

http://www.mouser.com/catalog/specsheets/715p.pdf

Panasonic Caps:
https://www.mouser.com/Search/CompareProducts.aspx
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on November 13, 2018, 11:59:15 AM
Apparently, pulse voltage is the concern when using the little yellow caps we use in radio.  I'm told that the orange drops handle pulse voltages better.  I have some 1000 volt orange drops at home that I got for the coupling caps that RCA liked to use in some of its radios.  Now that I have a legitimate need for 1000 volt orange drops, nobody makes them anymore.  The .056 is rated at 400 volts, so the 800 volt ones you found should work fine.  There are a couple of boost caps that are rated at 1000 volts.  I was going to increase those caps to 1600 volts.  Those are common values and no problem to get.  My best bet may be to order those and the Nichicon PZ's I'll need to restuff ecap cans from Mousers all in one order.  They way it looks now, Sal should be able to supply the rest of the caps I need.  I want to replace all the 1/2 watt resistors in the chassis with one-watt.  RadioDaze has those.  Thanks for your help, Danny. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on November 13, 2018, 06:15:49 PM
I have gotten in considerable "card table" time in on the chassis this afternoon.  I say card table because I don't have a bench here.  My long-suffering wife has me all set up in the den.  I tore my Buick down and put the parts in the spare bedroom when I restored it 22 years ago.  So this is nothing new to her.  No effort too great for a Magnavox.   ;)


I have also confirmed by scientific evaluation that this TV would have never worked in the condition it is in currently.  There is LOTS wrong with this thing.  LOTS.  I have resistance measurements all over the place.  The 6GC5 having bad connections from the tube socket to the PCB is a big deal.  It has basically killed B+ to both 6BZ6 IF amplifiers.  And it has killed B+ to the audio board.  As I work, if I kinda pry on the tube socket connections, I can get my reading to change.  I got a magnifying glass and found that a considerable number of the tube socket connections are suspect.  Possibly a good plan will be to reheat every tube socket connection, with emphasis on the ones known compromised.  I found a digital multimeter in my junk drawer I did not remember I had.  I like digital meters for measuring resistance.  It is brand new and probably 30 years old.  The 6GC5 in this chassis serves as a voltage divider, supplying B+ to several circuits in the chassis.  The procedure I am using on this chassis is against the good advice of those who know a whole lot more about this stuff than I do.  In deference to their greater ability, I can say that I would never live long enough to do a couple components at a time then re-install the chassis to see if I helped or hurt it.  Shotgunning this thing and repairing everything found wrong is the only way I can see of doing this in a reasonable time.  I sure hope that turns out to be a sound decision.  I don't see why or how this chassis got in such bad shape.  It appears to have not been messed with, other than having the tubes replaced.  Every soldered-in component appears to be put there by the factory.  When you fix a mess, it is more rewarding.  Gloriously Complicated!  We shall forge ahead.......



A theory that may be borne out by further investigation is this.  Could it be possible that the hands that replaced all the tubes did so in such a manner to damage the solder connections on the PCB?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: 19and41 on November 13, 2018, 07:33:02 PM
If those tube sockets are soldered directly to board traces, you can rely on fracturing.  Check continuity between exposed and coated traces also.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on November 13, 2018, 07:42:17 PM
I am going to finish running the resistance on the tube pins, per the Sams document.  Then I'll replace components and pay careful attention to the solder joints on the tube sockets.  I'd say the tube sockets are directly on the board, if I understand your comments correctly.  I appreciate your input, Rex. 


I can probably safely say there is considerable difference in the build quality of Magnavox audio equipment and their TV sets.  I can't believe this thing was built by Magnavox. 


I seem to have misplaced my component color chart.  The one I use to identify the markings on resistors.  I know black is zero, brown is one, red it two, yellow is three, orange is four, but after that I always have to check the color to refresh my memory.  Would any of you be good enough to refresh my memory?  I have no idea what happened to mine.  I used it the last day or so, and this afternoon it came up missing.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on November 13, 2018, 08:25:50 PM
Maybe Mittens is playing hide and seek with it.  ::)

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: SeniorSteve on November 13, 2018, 08:28:56 PM
0 - black
1 - brown
2 - red
3 - orange
4 - yellow
5 - green
6 - blue
7 - violet
8 - gray
9 - white
In vocational school I learned a little ditty that helped, but I can't print it here.

 :D
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on November 13, 2018, 11:22:48 PM
Thanks, Steve.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on November 14, 2018, 10:46:58 PM
The printed circuit chassis in this TV is a little different than those I have had experience with.  This one has the traces on the back (non-tube) side of the chassis, with component symbols and identifying numbers.  The identifying numbers are then repeated on the front side with the component so you can easier identify the parts.  Both kinda neat and kinda confusing until you get the hang of it.  The boards themselves appear to be better quality than those in, say, a GE clock radio.  Zenith bragged, rightly so, about their handwired chassis.  This chassis appears fairly easy to work on so far.  A couple parts are rather tight, but I've seen worse on radios.  Rex offered advice on watching out for the traces themselves.  It appears like there are reinforcement doodads on the tube pin connections to the circuit board itself.  I'm sure that is not the correct nomenclature, but I don't know what else to call them.  The bottom line is that these things may prevent the condition Rex was talking about.  What few of these I have checked, per his suggestion, have checked okay.  I can't say "most" yet, but I can say that several of the tube pin connections have cracked solder joints.  I just don't know why yet.  Could someone moosing around on the tubes trying to get them out, actually have damaged the tube socket solder joints?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on November 14, 2018, 11:26:06 PM

In vocational school I learned a little ditty that helped, but I can't print it here.

 :D

The same thing goes for marine navigation using a compass and chart.  There are ways to remember what you do when moving from true to magnetic to compass readings or back again.  Some are not suitable for polite company but they are memorable.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on November 15, 2018, 05:58:55 AM
Sounds like things are moving forward.  With it being Magnavox, which means quality, it should be over built and made to last.

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on November 18, 2018, 12:16:35 PM
My friend, the cabinet refinisher, in Missouri called this morning.  He is 95% convinced that the cabinet on the Stereo Theater was originally finished in lacquer.  This is inconsistent with what we believed in the past.  Magnavox had the bean counters working overtime in 1962, so it is very possible that the "10 coats of hand-rubbed finish" was one of the casualties of that effort.  We know that the speakers, tubes, remote control chassis and the MPX chassis were outsourced.  It has also been determined that there is a good possibility that my Stereo Theater cabinet was not built my Magnavox.  The main reason for this belief was that Magnavox used a closed-fiber type of particle board in their cabinets for sound deadening rather than the open-fiber material found in this one and that is deteriorating.  There are also joints in this cabinet that were not used by Magnavox.  The reason we believe this cabinet may have lacquer on it is by evaluating the environmental damage to the finish and by the fact that lacquer thinner easily removes the finish.  It typically requires acetone to remove the finish on a Magnavox cabinet.  Tar and nocotine, combined with less-than-ideal storage for a time seems to have damaged the finish.  In fact, mineral spirits will remove the finish on this cabinet in most places.  This discovery presents the hubs of a dilemna.  I detest lacquer and avoid its use.  So, do I refinish correctly in lacquer, or use poly and shellac like I had planned.  Or a combination of the two.  I have also found an ecap can in the HV section of the TV chassis that is marked, and appears to be a two section cap.  The parts list in Sams shows a three-section cap.  Another Sams error or do I have a "Mystery Magnavox" like others on this forum have.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on November 18, 2018, 12:43:11 PM
My '56 devices and the 1951 +/- one have lacquer finishes too.  It was the standard furniture finish of the time.  On my old radios that are in rough shape, I tend to use oil-based varnish.  Not spar varnish; that is softer so it can accommodate wood movement that comes with a marine environment.  Interior varnish.  I like it because  can brush it on and then wet-sand it  and polish it up with pumice and rottenstone (or automotive rubbing compound if that's wat's at hand). 

Lacquer finishes can be rubbed out too.

And if you have somebody else doing it with proper equipment, it would be like-new.  Or if you have spray equipment and an adequate booth.  I just like the brushed varnish because I don't have that stuff.

At least one of the under-bumper valences on the Chevy still has acrylic lacquer that I sprayed on using a vacuum cleaner and its spray attachment (!!).  I actually got pretty good at wielding that device when I was in high school.  Maybe that was the original HVLP device.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on November 18, 2018, 02:12:05 PM
This one will likely get a lacquer finish when all is said and done.  Lots easier than poly if you do it right.  Not very durable, and we have cats..... ;)


I have the resistance measurements done on the chassis and have gone back over resistances that appeared out of range.  Most of those can be attributed to bad tube socket connections and/or aging components like resistors and capacitors.  I have not found anything shocking or "terminal" yet.  Just lots of little faults that, put together, would render this chassis as a non-working TV.  I am using parts of two diagrams, Sams 591 and Magnavox factory literature.  The Sams' document is a little easier to read, the Magnavox document is a little more correct.  Why would I use a diagram that is wrong, you ask?  I have actually found them both to be wrong in a couple instances.  I am working on a "Maggotbox".  I have already found a resistor on the 6GW6 Horizontal output tube, that is different on the chassis than what is shown on the print.  I believe the one on the chassis to be original, so I'll go with its value rather than what is on the print.  I have a hunch that this is not the only instance where I'll find something similar.  So far, so good.  "Gloriously Complicated"......   :) ;)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on November 20, 2018, 07:46:22 AM
"Gloriously Complicated" and a "Mystery", all rolled into one.   ;)

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on December 02, 2018, 03:12:58 PM
I have been measuring resistors.  After running all the circuit resistance measurements, I went back over everything and figured out why any out of spec resistances were like they were.  I have been measuring resistors on the individual circuit boards and have not found all that many out of spec.  Maybe less than a dozen so far, out of 40 or so.  I have two 3900 ohm resistors, in different circuits and on different boards, that test zero ohms.  That seems too coincidental to me.  I will investigate further. 


My "operating" conditions are not optimal.  I sure miss my bench.  I also understand why TV guys like jigs to mount the chassis on.  If this thing works after being restored on a card table...... :-[
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on December 02, 2018, 05:42:51 PM
I'm ready to put a parts list together.  I believe I can do this in two orders.  It may not be as bad as I first thought.


I have some clean-up work to do, including figuring out what the deal is with the two 3900 ohm resistors that check open.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on December 02, 2018, 06:31:51 PM
Well, if they're in the same device and have the same value, they were probably manufactured in the same batch.  Maybe there was some glitch that day.  Or it was Monday, or the company got a bad delivery of carbon, etc.  Maybe you should replace ALL the resistors of that value.

And the card table... that was my workbench for the Chevy carb rebuild, too.  The engine rebuilder (a wise man) rechecked my work and found a float bent a bit outwards so it was catching up on the bowl.  I blame it on bending over the card table.  Surely couldn't be my own ineptitude.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on December 03, 2018, 11:38:15 AM
This TV could not possibly have worked in the condition I got it.  It may never have worked right.  The card table is at an odd working height.  I reckon my radio bench would make a lousy card table, in fairness.  I reckon they call it a CARD table for a reason.  They don't call it a TV chassis table for a reason.   :)


And, it may not work right after I putz with it.  I have to keep a good thought.   ;)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on December 03, 2018, 06:29:28 PM
Well, as long as you get your capacitor polarities right and don't connect something to the wrong lug, it's not likely to work WORSE.  And even if it's not perfect, you can always track down an old-TV guy to do the final diagnosis and repair, the kind that requires specialized knowledge and tons of experience ("That's the model where the IF transformer always went intermittent," that kind of thing). Then you will have narrowed the possible defects way down.  Like the open resistors.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on December 04, 2018, 02:41:04 PM
I'm the only "old TV guy" in my neck of the woods for several hundred miles.  This has been a learning experience for me that I have looked forward to for a long time.  I'm not sure if I'll ever work on another TV, but I want to do all I can to get this one going as well as I can.  I appreciate the confidence you have in my ability.   :)



Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on December 05, 2018, 07:35:07 AM
Speaking for myself, and I'm sure others here on the forum, we are routing for you.  And when you get this on under your belt, the skies the limit.  ::)

Bill

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on December 08, 2018, 11:28:01 AM
I have measured all the resistors in the TV chassis.  I am using a calculator to figure out the percentage of drift I measured.  An odd fact I have found is that all the resistors I've calculated so far have drifted tenths of a percentage on either side of 9%.  There are those that should have closer tolerance than 20%, so these I'll go back over to determine if they are far enough out of tolerance that they should be replaced.  I'll note which these are and will go accordingly.  I was expecting more out-of-tolerance resistors than I'm seeing so far.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on December 08, 2018, 12:19:31 PM
Maybe I'm just fumble-fingered and inept, but it's awfully easy to damage things when replacing soldered components.  Some of them can very very hard to disentangle, even with good desoldering techniques.  Maybe it's best to focus on just those that are way out of spec, especially where the specs called for close tolerance, indicating a critical component.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on December 08, 2018, 01:47:48 PM
I have gone back thru the resistance to ground on the low voltage, sound, IF, and sweep boards.  The reason resistances are off is due to the poor solder connections on the 6GC5 voltage divider tube.  I have run back thru the individual resistor measurements and have investigated any that were out of tolerance.  The 3900 ohm resistors I thought were open actually were okay.  One should be cognizant of meter settings when going from megohms to lower ohms.  I did not have my meter set correctly, and therefore got wonky readings.  This is where having my typical five or six VTVM's fired up at once on the bench is of advantage.  I avoid such errors.  No harm was done except some wasted time and some skinned-up pride.  I have done the LV, sound and IF boards with the individual resistors and have yet to find one out of tolerance.  I believe, at this point, that if I recap and fix that socket with the bad connections, I will be closer.  I wonder if this is a fairly low-hour chassis that has suffered from "happy hands at home" considering that wholesale replacement of all the tubes.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on December 08, 2018, 02:38:59 PM
I have gone thru the resistances to ground and resistors on the sweep board and the HV section.  Like previous boards, the resistance to ground readings are acceptable, considering the bad socket connections on the 6CG5 tube.  Is it possible there are NO resistors in this entire chassis that are out of range?  Is it even reasonable to consider the fact?  I have lifted one end of certain resistors that appear to be out of tolerance when I found they were in parallel with another component.  All have been okay up to this point.  All have been within 10% of spec.  Certain resistors with closer tolerances have been checked and have been found okay.  I suppose when I get the chassis back into the cabinet and connected to the CRT, I'll discover how accurate my work has been.  I checked more than once.  Hmmmm....... :-[


The plan right now is to get my parts order finalized and get the parts.  I'll recap the chassis first, then do the electrolytics last.  I have to figure out a way to get the high voltage cage off before I can restuff one of the electrolytic can caps.  I'll recap and clean, recheck my work ad nauseum, then take this thing home in the spring and see what happens.   


My first idea was to replace every resistor and every capacitor that was not a ceramic disc in this entire chassis.  Cooler heads prevailed and suggested that more harm to the PC boards might be done than might be gained by such a plan.  If my work so far has been accurate, replacing every component would have proven a huge waste of time.  If I have to dig this chassis back out of the cabinet to redo my hack by not changing everything, I may not be too proud of myself.  "Gloriously Complicated".......... ;) :)


I have learned that the folks who work on these things with more experience than I have (everybody on the planet who works on these things! :) ) leave cleaning controls until the chassis is powered up and a fault has been found.  I don't want to fool with the settings in high voltage and that and upset the operation of the Magnalux system.  I have a vague idea of how it works, and know just enough to leave it alone until I have an issue.  Then I'll ask for suggestions on how to proceed from that point.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on December 08, 2018, 03:34:38 PM
I need an .0039 at 200 volt cap in the sweep section.  All I have been able to find is either .0033 or .0047.  Wonder how critical the value is.  Everything else I need Sal has.  I suppose Mouser's is my only option?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on December 08, 2018, 03:41:51 PM
Or do a quick Google search to see what pops up.  Never can tell.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on December 08, 2018, 04:11:41 PM
I found some at Mouser's.  I need a break from their website.  Horrible.  The only word I know to describe it.  If I need to deal with them, I'll probably restuff with PZ's.  I love those things.  I'm referring to the PZ series of e-caps from Nichicon.  They are skinny enough I can restuff a four-section can, no problem.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on December 08, 2018, 08:28:14 PM
The only reason I suggested Google is that I often overlook it as a way of finding odd things.  This spring my Mom's Subaru had not been run in a while and the battery was almost dead.  In trying to start it  we got the voltage below some critical minimum and all 4 parking lights started flashing.  Nothing would make them stop except disconnecting the battery.  Recharge, reconnect, and there they went, all 4 flashing no matter what I did.  So my sister did a quick cell-phone Google search on something like "Subaru lights flashing."  There was a quick tutorial.  It involved pushing a button on the underdash computer box while turning the ignition switch.  Damned if it didn't work.  Saved a trip to the Subaru dealer ($$).   Since then I've tried to remember just doing a Google search.  And for little components, eBay sometimes has them and it can be easier than a Mouser order.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on December 09, 2018, 11:54:35 AM
This chassis uses a 130Uf @200 volt ecap that appears to be an odd value.  It does not follow the rectifier, so I can increase it to 150uf @ 350 volts, which is a more common value.  I can get the coupling caps I need from Sal.  I prefer to give him my business whenever I can.  Part of the problem I was having with the .0039 was that I was looking in orange drops.  They do not make it in that value that is convenient to obtain.  I like simple.  Anything I perceive to be unnecessarily complicated I avoid.  I am being careful with component values in sweep areas and where I know exact values to be important.  I'm learning, albeit slowly......  "Gloriously Complicated".
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on January 19, 2019, 05:30:53 PM
I'm planning on recapping the chassis, then working with electrolytics.  That seems simpler.  I got all the caps I need so far at Sal's.  The electrolytics I will have to get at Mouser's or somewhere. 


I have not established a baseline on this chassis, due to obvious defects that will keep it from working.  I am working on the card table in my little den.  Much like restoring your '65 Mustang out in the backyard under the old oak tree!  Since this is my first TV repair, I don't have enough experience to be afraid of anything.  I have eight pages of notes made on this chassis.  Hopefully, if I have some type of issue when I get the chassis back in the cabinet, I'll be able to refer to my notes and figure out if I made a mistake, have a defective component, or if something I did not work on is the problem.  My goal is to get the picture tube to light and to hear some type of sound from the TV out of the speakers.  I am taking pictures as I progress, so stand by.  Here we go........ :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on January 19, 2019, 07:54:12 PM
While Chris is working on his radio on a table saw, I made progress working on my TV chassis on the card table.....


I got all the caps except one changed in the HV section.  No big deal so far.  I have been double-checking my work, one capacitor at a time.  After I get the lone holdout replaced, I'll run resistance checks in that section to make sure everything is okay.  I am retaining the old parts just in case. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on January 21, 2019, 05:24:41 PM
I have a question.


I have read on other forums that a B&K model 1076 TV analyzer is the bomb for working on old tube TV sets.  I see they are available on the 'bay for not too much money.  I also see a model 467 CRT tester like a guy I follow on YouTube uses.  I digress....


How does the 1076 work and how would it benefit me in my "relentless pursuit of perfection" on the Magnavox chassis I have been working with.  Or would there be little to no benefit.  The TV guys really like these things when working with a tube color set.  Are they of less benefit on black and white sets, or is their use overkill on black and white sets?


From what I have seen of these things, they are housed in a big box with maybe 12 to 15 tubes plus a CRT.  The CRT appears to be inside the box with no way to view it from the outside of the box.  The front of the cabinet just has controls on it.  I'd have to have a manual for one to figure out how to use it.  Anybody had any experience with one or knows how they work?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on January 22, 2019, 02:22:41 PM
I have all the coupling caps changed, except one I could not see the value of.  I got a bigger cap out of the way, so now I can see the value.  .005 uf @ 200 volts.  I'll get one of those when I get the damper socket.  That project is next, followed by replacing all the electrolytic caps.  The one I could not see the value of is on the sweep board.  There is a shield soldered to the chassis over the back of the IF board.  I'll recheck the resistances again, then replace the shield.  I repaired the poor solder joints on the 6GC5 voltage divider/cathode follower tube on the sound board.  I'll recheck the resistances and see if I made any difference and/or if there are issues I caused by shotgunning all the caps.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Motorola Minion on January 22, 2019, 04:18:51 PM
Greg, The B&K 1076 and later 1077 are test pattern, color signal and sweep substitution generators from the 1970s. I used one in HS to confirm the flyback in a 1962 Silvertone color (RCA CTC11 clone) was fried. Back then, going into the supply house and asking for a 16 Y.O. part for a Sears would get general surliness and a $75 estimate to back-order one, no money back.

The TV Analyst IS the bomb when you have to trace out problems all through a BW or color TV. With the thoroughness you are restoring the Magnavox, you may not need it. I also have a Sencore VA-48 that is a similar help on anything pre-1980s, and even has a coil-ring test for flybacks and other transformers. It helps me check IF-video-color alignment and perform it without much fuss, as was the case if using marker adder and sweep generator. Less chance of un-dialing some slug that was OK IMHO

If you are testing CRT's the 467 is a more complicated and trouble-prone tester than a Sencore CR70 or an earlier BK, say a model 460. I like to keep my old 445 for the older sets, its more telling of condition.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on January 22, 2019, 04:46:57 PM
I have a B&K 445 CRT tester.  I don't know if it is accurate, nor really how to tell if it is/isn't.  I'm not even sure I know how to properly use it.  That said, I read about the analyzer, and, realizing that I am just starting out, wondered if it would do me any good to have one.  It's a neat looking contraption, full of tubes.  Thanks for your input.


I have run the resistances again after changing the caps.  Everything is what I would consider okay with the exception of pins 1,8, and 9 on the 6GC5 and pins 6 and 9 on the 6EM5.  I have fixed the opens on the 6GC5, but I'm not out of the woods yet.  I suspect an electrolytic cap may be the problem there.  The pins I mentioned on the 6EM5 test open.  I'll check the circuit involved with those pins and figure out what the deal is.  I'm getting close.  I want to figure this out before I do the e-caps.  I don't want to take the chance I may have introduced a fault.  I checked each cap after I changed it to make sure I had a good solder joint.  This is not the easiest PCB I have seen to solder on. 


I have several pages of documentation on the work I've done on this chassis.  Before and after resistance readings.  Readings on every resistor in the chassis.  I can't leave anything to memory.  I'm not sure how much good all this will do me, if any, but it sure looks impressive to see how much work I've put into a TV chassis that will still be obsolete after I put this much of myself into it.   :-[ ;) :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on January 22, 2019, 05:09:15 PM
Dave, what is the purpose of the picture tube in the 1076? 


I may have some shorted, or severely leaky electrolytic power supply capacitors in this chassis.  Pins 1,8, and 9 on the 6GC5 only have those caps between them and chassis ground.  This tube is used as an audio output tube in some versions of the C36 series chassis, but in this particular version, it is used as a voltage divider and cathode follower. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on January 22, 2019, 07:16:07 PM
Part of my problem was self-inflicted.  My notes have already bailed me out.   :)


I was going thru my notes on what I had done up to this point.  I saw a notation on the notes where I took resistance measurements "Tubes in place."  Oops.   :-[


I had taken several of the tubes out in order to give more room to work replacing the caps.  I had not put them back.  I noticed on the schematic that pins 3 and 6 on the 6EM5 were connected internally.  Putting the tube  back fixed that problem.  I read an open on pin 9 in my "before recap" resistance checks.  I read open on that same pin after the recap.  I wiggled the tube and found the needle on the ohmmeter bounced around when I wiggled the tube.  The spec on pin 9 is 450 ohms from that pin to the output of the rectifier.  I now have 16K ohms, which is way too much, but is less than having an open.  I won't worry about that at this point until after I have the filter caps changed.  And after I replace the 6EM5 with a new tube.  I still need to figure out the issue with the 6GC5,


I found this on the TV analyzer. 


https://antiqueradio.org/BK1077BTelevisionAnalyst.htm
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Motorola Minion on January 24, 2019, 10:50:37 AM
The video is from Phil Nelson, a long-time member of videokarma, ARF and other forums. He like s the old stuff like us but also is a font of practical advice.

The CRT inside the analyst is a camera tube of sorts. The test patterns are on sheets that go against the face of the tube. The color bars are generated as in most of the color-bar generators like the RCA WR-64.

B&K was known for making equipment that allows for the flexibility to service not just TV but any type of monitor. Sencore equipment was geared more toward the TV repairman than AV techs and broadcast engineers.

For your 27" Magnavox BW that B&K 445 is perfect! It tests color also.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on January 24, 2019, 07:57:12 PM
I have a friend with a 1077B for sale.  I may reach out after I get home in the spring.  It would be fun to play with if nothing else.  I don't have any way of making any kind of width or linearity adjustments.  I'm not convinced that this TV chassis has not had some "screw twisting" in its past. 


I learned something while I was servicing the PCB chassis.  Everybody else on this forum may have known this, but now I do too.  This particular chassis has the printed wiring on the back side with the components on the front side.  There is component nomenclature on both sides of the chassis, allegedly so it is easier to service.  All the printing on both sides makes the chassis look "busy" to me, making it actually harder to locate the components you want to work with.  I removed a capacitor, then could not find the holes in the PCB so I could put it back.  My wife was holding the flashlight and accidentally shined the light toward the chassis.  The holes I was looking for jumped out at me!  This make it very simple to locate the holes with all the junk on the chassis.  Shining the light from front to back makes it easy to follow the printed wiring in order to trace out the circuit.  It was recommended that I use a solder sucker when desoldering on a PCB.  On this particular chassis, I found it better to not use the solder sucker.  Leaving the little piles of solder from where the component was removed aids in finding the hole from the back of the chassis.  Magnavox's idea to put component nomenclature is good if you are trying to find a specific component.  It is not so helpful when removing components for replacement.  The first cap took 30 minutes, the rest of the chassis didn't take much longer than that.


I'm not going to try to clean any of the controls until I power up.  I have heard about "tinwhiskers" messing up controls and that, but I'm not going to worry about that now.  I'll deal with dirty controls after I get it going unless someone sees a good reason to change that plan.


Thanks, Dave, for the explanation of what the picture tube in the analyzer's purpose is.  That makes sense now.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on January 25, 2019, 06:10:45 AM
That's a good idea Greg, something I had not thought of.  But, I also have not worked on any PC boards yet.

Bill

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on January 25, 2019, 07:52:36 PM
I''ll admit that most of the PCB's I have worked with are RCA or GE.  They both have silver printed wiring that is easy to trace.  Magnavox makes their printed wiring almost the same color as the board.  PCB's are not necessarily harder to work with, but they are different than hard-wired.  It is not as likely that you would make a miswire with printed wiring.  If you put a light on the opposite side you are working with on a Magnavox chassis, you can easily see what you are looking for.  There is no reason to be afraid of one.  You should be careful with soldering iron heat. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on February 03, 2019, 02:22:48 PM
I have a question for Dave or whomever would care to chime in.  I have no experience whatsoever handling "dangerous" picture tubes, so please bear with me.


How heavy might I expect the 27ZP4 picture tube to be in my Stereo Theater?  And I read somewhere than if I were to remove a certain "band", the CRT might implode!  I don't need that.  I plan to remove the two braces holding the CRT at the top, then remove the four bolts holding the frame for the CRT into the cabinet.  This after removing the safety glass and mask from around the CRT in the cabinet.  I plan to borrow a welder's face shield and some long welder's gloves.  Then I guess I'll hug the CRT and bring it forward out of the cabinet.  Then store it on its face laying on a blanket to protect the face.  I'm figuring that if I don't neck the tube, I should be safe.  Any thoughts?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on February 05, 2019, 10:39:54 AM
Hi, all !  Back again for  week or so.   I think that band you were mentioning, Gregg, is a steel metal strap around the largest diameter of the CRT on the edge of the viewing screen,  nowhere near the neck. It has some kind of retaining snugging up kind of arrangement on it that looks like on a packing crate. It prevents the glass from being put in tension, where it is weak, instead of compression, where it is strong, if the CRT would get a jolt to the flat face somehow. More later time out
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on February 05, 2019, 11:20:28 AM
  As usual I am  on the motel computer with the timer running out all the time, so I have to post without proofreading.  I seem to remember reading in some old TV trade journal that the larger CRTs with high deflection angles would occasionally implode if they got a sudden jolt to the flattish front face. Like an angry teenager's foot after the wrong team won a football game, haha. The angle of the nearly flat face would multiply the inward pressure enormously and apply it all to spreading the glass outward at the broadest diameter of the glass which more than overcome the inward pressure on it from being under a vacuum  The steel band looks like what you see around wooden packing crate where a gadget crimps the band in a sort of a permanently buckled strap. There is actually a shallow groove in the glass so the steel band can't slip out. Don't worry about accidentally taking it off, they just don't come off without some kind of grinding wheel.
          I have seen underwater sonar transducers with the same kind of arrangement and it was for the same reason....so that the ceramic elements would always be under compression, where they was very strong, and never under tension, where they were very weak. Sometimes they had a strong bolt (beryllium copper) and nut going through the center of hollow doughnut shaped ceramics with Belleville washers, the ones with a curved shape, and tightened to a certain prestress torque. Time out again !!!!   
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on February 05, 2019, 12:19:14 PM
Thanks ED, I know this will help Greg.  Now that you mention it, way back in the day, I remember the band around the tube.  The ones I remember had the bolt/nut that tied the band together.  They were color sets, RCA's.  Is the front glass thicker on a color set than B&W?  I don't remember that either.  Old age I guess!  :(

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on February 05, 2019, 04:23:48 PM
   Somewhere in the early sixties, they began placing the safety glass  (tempered) integral with the picture tube glass with bonding cement joining them, like a car front windshield. Sometimes they disbond a little near a corner and then you see a kind of cloudiness in that area. the glass also had a tint to it so that reflections from room lighting got attenuated twice, one in each direction but the light out of the CRT only got attenuated once, in the in to out direction, which improved the contrasat ratio.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on February 05, 2019, 05:09:30 PM
I am reviewing the pictures I took last summer.  I see that band you are talking ab out.  It is in a groove near the front of the picture tube.  It is under the bracket that holds the picture tube to the cabinet. I won't mess with it.  The CRT sits on a bracket that is bolted to the cabinet.  That bracket has a strap that goes around the CRT to hold it to the bracket.  There are two straps from that strap to the back of the cabinet.  If I understand correctly, as long as I don't mess with the band on the picture tube and that I don't neck the CRT, I should be good.  I see guys on the Internet toss these things around like soccer balls, but for some reason I'm not too sure of myself here.


The safety glass comes loose from the picture tube face.  Dirt enters where the bond is poor, creating the infamous cataract, most often seen on color roundie CRT's.  I have not seen that on a black and white CRT for some reason.  My ST has a thick piece of glass in front of the CRT.  It is held in by a couple of metal strips.


Thank you all for your input.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on March 12, 2019, 06:15:40 PM
I changed the damper tube socket this afternoon.  I had been putting this project off.  Following the advice I had been given, I removed all the pins in the socket that were unused.  This done to prevent arching between pins.  I left pins 3,5,7&8.  I'm all done except that I need to find some shorter screws.  I performed resistance checks to make sure my connections were all good. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on March 13, 2019, 10:18:42 AM
Progress is always a good thing!  ;D

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on March 18, 2019, 11:04:55 PM
I have been watching a video about rehabbing a 1962 Zenith TV.  The man on the video recommended replacing any diode in the horizontal or vertical sweep circuits.  Failure of these diodes can be expected.  He recommends their replacement being routine, like capacitors, resistors and tubes.  This TV chassis has one on the sweep board.  "Dual Selenium Diode, Series Horiz. AFC".  I found the diode on the chassis.  It appears to plug into a block of some kind.  There are no values on the schematic for this diode.  I'm told on the video that the recommended part comes from the power supply board of a computer.  This part is "X2" on the schematic and parts list if anybody is following along.  The part he replaced in the video had two diodes in one package.  The diode in my TV chassis has a "+" on one end and a "-" on the other.  It appears to plug in and also appears to be a dual diode.  The diode in the Zenith in the video got its diode replaced with two separate diodes.  There was no value given for this diode, he just pointed to the one on the computer board he was going to use, then showed what it looked like when he was done.  Can anybody give me an idea what diode could be used to replace the one I have?  This dual diode appears to be in the 6CG7/6FQ7 horizontal multivibrator circuit.  I am told that horizontal and perhaps vertical sync can be upset if these diodes have failed.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on March 19, 2019, 07:13:33 PM
The consensus of those more in the know than I is to not make trouble that may not exist.  This is one of those "wait and see when you power up" type situations.  Odds are the diodes are okay.  It has been noted that Zenith had a problem with diodes in certain models, but apparently it is not throughout the TV industry.  So we'll leave these be until we find a reason to doubt them.  I am going to replace all the tubes in the chassis with new ones, tested ad nauseum to make sure they are the best I can provide.  We'll clean up a few loose ends, replace the electrolytic caps in the chassis, and move on.  I'll clean the tuner once I get all the components out of the cabinet.  Gloriously Complicated.   ;) ;)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on March 23, 2019, 01:03:53 AM
         In the mid 70's, I had a Zenith TV with that same dual diode in the horizontal oscillator section. I think the tube was a 6GH8 triode-pentode tube instead of the more usual 6CG7. The diode was a black rectangular potted thing with three pins in a row along one side, and it plugged in a small socket on the chassis.  It compared the sweep circuit of the TV to the sync signals from the video of the TV signal and locked the oscillator frequency  to the TV signal. If the diode was bad, the signal wouldn't lock in--it would roll like a mis-adjusted vertical hold control, but horizontally  instead of vertically. But way back then, I actually was able to get the Zenith replacement part at good old Baynesville Electronic. They had it in stock too, it must have been a common failure item.
          I think a high voltage pulse is applied to them, maybe 60 volts or so from a winding on the Horizontal output transformer, , so you probably can't use a 1N914 or small signal diode, they may break down. But I don't think a power supply rectifier would work well either, like the    1N4003 thru 1N4007 series or at least they don't have to work because I don't think they have a spec for reverse recovery time or whatever is the spec for a switching type diode. You never know what you get, date-code wise when you buy an older diode. 
             When I was at Westinghouse, testing replacement modules used i pulse-adder circuits for military radars, , they had 1N486 diodes, (usually seen across small relay windings to absorb switching transients), used in fast pulse circuits, and the TX versions, which were JAN milspec versions, were horrible at switching pulses. It turns out there was no pulse spec for this particular diode, and something about the burn in procedure for this diode made it a slow-recovery diode. We had to switch all these pulse circuit parts lists to a different computer switching part number. It was a mess because the most they would do is list the better diode as an acceptable alternate, so you could still get more modules coming in to test with the old part number.  Time again...
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: firedome on March 23, 2019, 10:27:49 AM
Supposedly 6GH8s were a frequent failure mode in '60s color sets, particularly in certain RCA models that used like 5 of them. The TV gurus at VK recommend Sylvania 6GH8s as the most rugged for that application for some reason.

Ed what Wastinghouse did you work at? My wife's Dad was a Defense contracts (Navy) lawyer for them at the Friendship location, my neighbor growing up in Riderwood/Towson was an EE who worked at the Electric Motor location on Taylor Ave in Towson, and our neighbor in the '70s to '90 in Westminster worked at Sykesville, he welded space satellite chassis and stuff. He loved to call it Wastinghouse because they'd have to scrap a lot of really expensive stuff when the Enginerds changed specs after the stuff had been made already!
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on March 23, 2019, 12:42:11 PM
    Well, the answer to your question about which Westinghouse I worked at is....none of the above. I worked at the one in Hunt Valley, also known as Cockeysville until the gentrified bunch took over. It was about 6 miles north of the 12 0'clock position of the Baltimore Beltway, along the expressway to York,Pennsylvania, and a lot of W employees lived over the Maryland line in Pennsylvania, because taxes were less here, and another large bunch lived near Glen Burnie and Linthicum which is near what used to be called Friendship Airport along the expressway between Baltimore and Washington.  The main Westinghouse that designed and built all the military radars was near the airport, it's still doing the same business but it is now Northrup-Grumann. Hunt Valley was a satellite of the airport W, we built spare parts, maintenance consoles, and nuclear controls for the power plant division. Nuclear belonged to an entirely separate division, all we shared with them was a parking lot.
        A few of my Hunt Valley W friends are still at the airport one. I don't know of a Westinghouse along Taylor avenue, there is or was a Bendix there and there was a Bendix up a mile or two near the Baynesville Electronic store, that one built radars, military communications receivers, and used to be where all Bendix TVs and Radios were built, at least WW II and later. They might be Allied Signal now. Some of my Hunt Valley friends transferred to Sykesville and were there for years. I think Sykesville got a big contract for navy communication gear that had always been Raytheon or GEs for years but then somehow the original supplier got the contract back.
          Maybe the Taylor location was a field office ? There was also a Benson avenue W and a Landsdown W and a Bay Bridge W. Don't know much  about them, but occasionally a new person at Hunt Valley would say they were from one or the other so I got to learn them as Benson Avenue or Bay Bridge etc.
          Even though W is not trded on the stock 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on March 23, 2019, 12:59:49 PM
This TV chassis has both the 6GH8 and the 6CG7.  The GH8 is the phase detector and the CG7 is the horizontal multivibrator (oscillator).  The video I was watching was from my favorite TV guru, shango.  I have gotten so much useful information watching him work with TV chassis of all kinds.  Anyways, he recommends in the Zenith video I referenced that these diodes should be changed as a matter of course, like capacitors.  That was what started me thinking about mine.  This diode appears to be potted in a black plastic doodad that is soldered to the board.  I don't suppose one of these would be available anywhere new....... ;) ;)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: firedome on March 23, 2019, 01:17:08 PM
Doug Harland out in MI is a big Zenith guy too, he's helped out my friend in Canada with his '68 Stereo Theater's issues.

Ed I forgot to mention, besides my wife's Dad (step-Dad actually), her uncle Ken (her Mom's brother) lived in Linthicum and also spent his entire career as a EE at the Friendship location, now Northrop Grumman. He's 92 now and lives in Charlestown Retirement Village in Catonsville on Wilkins Ave.
 
I'd  forgotten about their Cockeysville location, W-house had a lot of locations! Taylor Ave was some kind of electric motor repair location, not a big plant, it was just 1 blk E of Loch Raven Blvd, near the  movie theater, in the back, not too far fromBaynesville Elec on Joppa.  Bendix was on E Joppa Rd, sort of across from Black & Decker. We lived just S of W Joppa Rd, 1 blk from Charles St. Been 1968 since I moved away - 51 years next August!!

 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on March 23, 2019, 01:20:42 PM
          Sorry, the computer timed out again. I remember an RCA chassis with lots of 6GH8s and they were probably used near their limits. I have read somewhere that tubes with little cathodes but high transconductance have short lives compared to an older design, like a 6J7. My radio club moderator, an old  guy, used to say things that were based on fact, though he couldn't give a reason why, One was "You can't beat them Hewlett-Packards." about test equipment, and the other was "Them old tubes, they never burn out." about old octal tubes and older. I think a lot of newer tubes didn't last long enough to get into real mega-mass production. I'm thinking of 6EU7 in Magnavoxs you mentioned always gave trouble.
        Gregg is your Zenith or your Magnavox TV schematic on downloads ?  I used to mess around with black and whites a lot and some color, but only the tube sets, and only adjustment type of things. The whole horizontal sweep circuit was a guessing game for me, usually the bad part would smoke or smell or make noise, but the other sections I could troubleshoot OK if I had the schematic. I forgot whose it was, maybe yours, but someone posted pictures of the cleanest Magnavox TV chassis I had ever seen, and I don't think I saw a PC board anywhere. It surrounded the picture  tube neck.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on March 23, 2019, 03:01:18 PM
There is a member on here who is doing another Stereo Theater with a hand wired chassis.  Perhaps that is the one you're thinking of.  If my research is accurate, 1962 is the first year Magnavox used PCB's in TV chassis.  This is the C36 chassis and it is in Downloads.  Mine is a "half chassis" in that it does not surround the picture tube.  I always thought the vertical Magnavox TV chassis were Zenith clones.  That might have been more accurate before they started using PCB's.  The entire sweep circuit is a mystery to me.  I have learned a lot from shango and I owe him a huge debt of gratitude for taking the time to post his excellent teaching videos.  I'd love to meet him in person.


I know all about the old "smell, sound, smoke" diagnostics.  I'd like to head that off, if I could.  My goal is for this thing to work right the first time with a few adjustments.  The guys on here have been great bailing me out of the various messes I've gotten myself into.  Even the guys on ARF have been helpful.   ;) ;) :) :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on March 23, 2019, 05:30:25 PM
I watched three more shango videos, and in every one of them, he talks about replacing the double diode used in the sync circuit.  I removed mine.  According to the schematic, this little ceramic block contains two "signal" diodes connected in series.  One end of the ceramic block is marked "+" and the other is marked "-".  Remembering that a diode is a one-way valve, I figured if I measure the diode one way, I should measure infinity or high resistance, measured the other way, I should get a reading of only a few ohms.  Any way I measure this one, I get infinity.  No resistance no matter how I measure it.  I have used two analog meters that I have here to eliminate meter error.  That tells me these two diodes are open.  What am I missing here?  Is that even possible?  Remember, I was under the impression this TV had not worked in forever, based on a couple other things I found.  What say you wise ones?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on March 23, 2019, 06:08:22 PM
I dug out a digital meter and redid my measurements on the diode.  If I measure resistance on each diode, I get a little over 2 meg resistance one way, a little under 2 meg the other, on both diodes.  If I measure across both diodes, I get 215K ohms one way and 232K ohms the other.  This makes no sense to me whatsoever.  I'm thinking I should get almost no ohms one way and megaohms the other.  What needs replaced, me or the diodes?  I'm saying the diodes need to be replaced.  What say you?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on March 23, 2019, 11:19:39 PM
I appreciate the advice and counsel people have offered me during this project.  This is one of those instances where I can run a little experiment, answer a couple questions I have, and maybe learn something in the process.  I'm going to find a couple of signal diodes.  I don't know if there are values on these things, nor do I know which value I need.  I'll just get a couple to play with.  I'll use a piece of perf board and make up a double diode.  I keep the ends of caps and components I cut off, so surely some of those will be large enough to make good connection in the plastic plug the diode connects to.  I can measure resistance on each diode, then on the two in series like in the original component.  If my made up component measures like I believe it should, then I have my answer that the one there now is bad.  If the made-up component tests like, or similar to, the one there now, then that will eliminate it from suspicion.  I'm still not 100% clear on how the sweep circuit(s) work, but if the components in the circuits are not good, they won't work. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on March 25, 2019, 02:55:48 PM
I have had the privilege of communicating with the Magnavox guru, whose identity shall remain top secret for the moment.  I have also found a NOS diode assembly should that become a necessity.  There are three different configurations of these diode assemblies, determined by schematic diagram and part number. The advice is to forge ahead like I knew what I was doing and, that should I have a sync problem sometime in the future, we could work thru that with no problem.  I'm sure learning a lot.


I have some pictures of the damper socket I replaced.  I used #4 stainless bolts and nuts.  I put some little rubber caps on the ends of the bolts, allegedly to prevent arcing, but mostly because I did not know any better.  They don't make tube sockets the same size.  The holes are different, the bolt locations are different.  Why could not sockets be made the same in all dimensions?  I had to get creative to make it work.  I removed the terminals from #1,2,4,6.  I only needed # 3,5,7,8. 


Most of you guys are not impressed with changing a tube socket, but I'm including this so I can document my project.  Thanks for bearing with me.   ;) :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on March 25, 2019, 06:59:08 PM
I'm impressed!  It looks very neat and tidy.  :) 

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on March 25, 2019, 07:18:02 PM
Thanks, Bill!  A step at a time.  Gloriously Complicated.   ;) :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on March 25, 2019, 08:27:28 PM

Most of you guys are not impressed with changing a tube socket, but I'm including this so I can document my project.  Thanks for bearing with me.   ;) :)

Actually, any of us who does anything along those lines knows how easily disaster can occur, and how often a simple project gets complicated... because the new socket is a different shape or has slightly different mounting-screw patterns or because of plain old orneriness.  Actually, I should say "how a simple project ALWAYS gets complicated."  It's the exceptional simple project that goes as planned.

What matters is that you are having fun, learning things, getting the project accomplished, and sharing info with us.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on March 26, 2019, 06:52:31 PM
I'm honored to be able to share this project with you guys.  I'm happy that you are enjoying it along with me.   :) :)


Rivets being used to hold the socket to the chassis would have been preferable.  I didn't know any way else to do it other than using bolts.  I hope I don't live to regret that. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on March 26, 2019, 06:59:43 PM
You could use steel pop rivets, or cut the extra length of the screws off with a Dremel tool and cutting wheel.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on March 27, 2019, 09:29:43 PM
I believe I'll try trimming those bolts a bit when I get home to my bench.


I got a little information from the "Magnavox guru" the other day.  One reason why Magnavox TV is held in low regard by the RCA and Zenith guys is that, back in the day, Magnavox eliminated the middle man.  You had the factory and the dealer ahead of the buyer. If you needed factory parts for an RCA or Zenith, you would go to the parts jobber and get them.  No so with Magnavox.  They were trying to keep costs down so they could compete after putting more money into the finished product.  The only place you could get Magnavox parts was from the factory or from a Magnavox dealer.  Many dealers did not handle a large stock of parts, again so they could keep their costs down.  Independent shops disliked working on Magnavox instruments because Magnavox dealers wanted to get paid to work on their own stuff, and hesitated selling parts to the independents.  So they shut out the independent shop working on Magnavox.  Sour grapes lingers to this day.  I am told that Magnavox provided excellent parts and technical support to their dealers. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on March 31, 2019, 12:04:11 PM
Peaking coils.  Little gimmick doodads that are put in the vertical circuit to tweak the frequency of the vertical circuit response.  More mystery doodads that never went bad when these old TV chassis were in service, but are frequently found bad nearly 60 years later when we try to restore them.  If these little coils are open, they can cause instability in the vertical and can kill the front end of the set entirely, both video and audio.  Not only are exact factory parts unobtanium, but many times the values for these little coils and the diodes that work with them are vague at best.  Here, my YouTube hero "shangoO66" works with peaking coils and give his usual excellent narrative of how he works with them.


https://www.youtube.com/watch?v=-ndVB-wCZEA (https://www.youtube.com/watch?v=-ndVB-wCZEA)


I'm not sure I have a problem yet.  These are the next things I'll try and measure when I get to my bench.  If nothing else, it will be a learning experience.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on April 05, 2019, 03:12:50 PM
Hi Gregg, back after another long absence. There is a good explanation of the RCA 630 chassis in the 1954 Audel's Radio TV service guide, one of those little red books Audels put out. It seems a lot like a description of an old-time auto ignition coil and circuit. Points close, current in inductance builds up to high value, points open, large inductive spike goes way up in voltage above the supply voltage, step up transformer winding  provides thousands of volts spike to fire plug. With the TV set, the horizontal output tube replaces the points, conducting heavily then suddenly cut off when a negative pulse hits the control grid. The high ratio step up winding goes to the HV rectifier to provide 15 KV or so, but there are two more circuits to the TV chassis. One is that the Horizontal output transformer is resonant about ten times higher than the 15 kHz driving waveform to the tube. Only half of one sine wave of the ringing oscillation gets to occur because the damper tube conducts on the first quarter c0ycle of the ringing and lops off the rest of the waveform, charging a small capacitor and creating the "boost" DC voltage that is usually twice the TV power supply voltage. That quarter cycle is the retrace of the horizontal scan line. The yoke coil goes to a low voltage tap of the HOT. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on April 05, 2019, 03:51:08 PM
          Before the 630 circuit, there would be a separate RF oscillator tube and step up transformer for the high voltage, but if you lost vertical and horizontal sweep, you would burn the CRT phosphor in the center of the screen where a bright spot would concentrate all the HV. They tried to make the high voltage, horizontal sweep and vertical sweep use each other's voltages to make it hard to damage the TV screen if one of the sweeps failed and concentrated all the electrons in a thin line on the screen.
          A TV sweep is 62.5 microseconds for one horizontal line, and 5 or so of them are used for the retrace time. During that short retrace time, a negative pulse cuts off the control grid of the CRT to make the retrace invisible, (also the video of a TV signal has a retrace blanking too) the HOT is ringing at the high self resonant frequency, the output tube has just cut off and the damper tube is hasn't yet conducted. The circuit is "on it own" during that short time, and that is when all those small capacitors near the damper tube and yoke are determining the various currents. Some of the voltages are so high a pulse, you can't even look with a 10 X scope attenuator probe. The plate of the output tube, the cathode of the damper, and the hot side of the yoke in particular have thousands  of volts, usually narrow hard to see pulses. Which is why I hope to find overheated  and toasty smoky components instead of trying to figure things out. Plus it's usually the horizontal transformer anyway.  One shorted turn will kill it, and there's so much ultrathin wire in the HV coil part of the HOT.  Out of time again !!
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on April 05, 2019, 05:01:25 PM
      Do you mean peaking coils in the video circuit ?   I don't know of any peaking coils in the vertical oscillator circuit. If the video peaking coils fail as long as they don't open up, they just smear the picture and make look like the fine tuning is misadjusted. Like the close-up shots of the faded Hollywowod starlet in the fifties movies, to hide the age lines. I think they held cheesecloth in front of the camera lens. 
     I see some coils near that damper tube socket that you replaced. If one of them was bad you would probably have poor horizontal linearity or a narrow width picture or higher than normal output tube current. I'm guessing the curr.ent to be 100 mA or so. Color TVs were more like 200 mA or so, but my memory is fading fast on those details.  I remember the horizontal linearity coil was adjusted for minimum cathode current.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on April 05, 2019, 05:44:54 PM
Just a note to say that's the most comprehensible explanation of the video circuits I've ever seen.  Great for those of us who a still somewhat theory-challenged.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on April 05, 2019, 07:59:25 PM
Yes, Ed, that WAS the best explanation I remember reading.  The peaking coils are a gimmick in the video circuit that influences the frequency of the video circuit.  I'm certainly not 100% on those, nor do I believe I need to be.  That is one of those "beware" components.  I don't need to know exactly what they do or how they work.  I just need to be aware of them being in the circuit and what happens if they are not up to snuff.  I worked on auto ignition for 40 years, and I'm not sure I can explain how the points and condenser actually work in auto ignition.  But I can troubleshoot and determine what I need to do to make it work again.  I am still EXTREMELY theory-challenged.  I am learning a lot.  And I thank you guys for your input in this project.  All these tidbits of information are vital to the success of the project.   :) :)


There are two phase detector diodes on the sweep board.  If I understand correctly, those two diodes keep the vertical sweep signal out of the horizontal sweep circuit.  If one or both of these diodes fail, horizontal locking may be difficult or impossible to obtain.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on April 05, 2019, 08:43:52 PM
I'm considering changing my MO slightly with the TV chassis.  Instead of finishing removing the components from the cabinet, then refinishing the cabinet before I fire the TV up, I may install the TV chassis and get a baseline of performance on the TV before I take the cabinet apart.  This will give me time to source potentially unobtanium parts if I find the need.  I'm interested in input on this.  The cabinet will be a big job, but I have put lots of time in the TV chassis and curiosity is getting the best of me........ ;) ;)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on April 10, 2019, 02:43:28 AM
I had a strange experience with those horizontal phase detector diodes years ago. In an early 60s Zenith B & W set it was a plug in gadget above chassis, smsall black, potted, 3 leads in line, dual diode symbol on it and one corner angled as a sort of basing diagram. The picture would not sync horizontally, just wandered left or right. I measured the diode with I think an old RCA VTVM (1.5 volt battery for ohms) and it measured open every which way.   I bought a new one, in stock, at Baynesville electronic which was encouraging since in stock probably meant common failure item. When I opened the plastic  the new diode measured open every which way too, but it just plugged in so I tried it anyway and that fixed the problem. I never did figure it out.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on April 10, 2019, 09:27:47 PM
The phase detector diode in my TV chassis measures weird like the one you checked did.  I have been advised that they are "always bad" but to wait and see  how it works before I get too concerned. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Motorola Minion on April 11, 2019, 01:04:30 PM
I'm considering changing my MO slightly with the TV chassis.  Instead of finishing removing the components from the cabinet, then refinishing the cabinet before I fire the TV up, I may install the TV chassis and get a baseline of performance on the TV before I take the cabinet apart.  This will give me time to source potentially unobtanium parts if I find the need.  I'm interested in input on this.  The cabinet will be a big job, but I have put lots of time in the TV chassis and curiosity is getting the best of me........ ;) ;)

Gregg,  I know someone upstate who has the entire insides including CRT of your set. I did not see if you tested it yet. I bet it works when you try it before a cabinet redo.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on April 11, 2019, 05:38:28 PM
 If its available on google, my words of wisdom about TV horizontal circuits were shamelessly lifted from the 1954 Audel's Radioman's and TV guide. Audel's has a knack for clear logical explanations of things that most other books either explain with calculus equations or are just out and out wrong, even if in legible words. They have lots of pictures, diagrams charts and exploded views of things that make the paragraphs make sense.
      Those phase detector solid state diodes are bad news as far as I'm concerned, they should have stuck to 6AL5s.  They are usually biased way into the non-conducting direction, 99  % of the time and then they get a very short duration very high voltage pulse from the horizontal transformer to make them briefly conduct. Meanwhile a rising (or falling) sawtooth wave if applied to their junction and a small capacitor is allowed to charge to, and hold, whatever voltage the sawtooth happens to be at during that brief conduction period. That capacitor voltage, now a DC voltage, is applied to one of the grids of the horizontal oscillator tube and makes the frequency shift in the direction to keep the sawtooth rectified part " in the middle" of the waveform voltage span and the whole circuit acts like an FM discriminator circuit feeding its average DC voltage back to the oscillator tube in an FM tuner with AFC. It's officially called a sample and hold circuit, I beieve although that wasn't used in the  Audel's explanation. Most Sams Photfacts schematics show the pulse and sawtooth waveforms on the schematic in the vicinity of the diodes. With such a dependence on pulse response and very low back resistance, its no wonder that the diodes don't measure so welll with normal voltmeter tests. They must be special diodes designed to work in those conditions.

  Oops  time to post or else
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: SeniorSteve on April 11, 2019, 06:44:09 PM
Those diodes are selenium and not germanium or silicon.  They come in several configurations, and when I was repairing radio/TV I don't believe I ran into any that were bad.  I would leave it as is until you start the TV up.  If you have problems with the horizontal being real touchy and not wanting to lock into the signal, then I would look at this.  As far as I remember, selenium diodes have a higher forward voltage and won't test reliably on a meter.  Here's a page from a 1961 catalog showing them.

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on April 11, 2019, 09:03:46 PM
Dave, Ed, Steve, thank you all for your input.  I have taken more time that really necessary with this TV chassis, partly because I did not know what I was doing, and partly because I wanted to learn.  This chassis appears to be fairly simple as far as TV chassis are concerned.  I have been following the schematic from power cord to picture tube.  I have at least a passing idea of how it all works, or is supposed to work.  I have been asking questions if I'm unsure about something and generally filling in the blanks.  Dave, I thank you for your encouragement and the heads-up on the extra parts.  I'll sure keep those in mind (written down in my notes).  I agree that the 6AL5 is probably simpler.  I may have found a set of NOS diodes should the need arise.  I haven't cleaned the tuner yet.  The "screen door spring" that grounds the 'dag coating to the chassis for a high voltage capacitor is wonky, so that needs to be sorted before I fire it up.  I want to get a Kill-A-Watt to monitor wattage.  The stereo and TV should draw something around 600 watts.  That will be easier to manage with a Kill-A-Watt.  I'm not planning on bringing up the voltage on the TV chassis gradually.  Turn it on at full line voltage and see what happens.  Monitor current draw to guard against something being amiss.  I have found a TV analyst, so I'm looking forward to playing with that.  I don't have any generators for TV, and that contraption is alleged to fill that bill.  I'm in the market for a high voltage probe/meter.  The ones I've seen are around $100 and this is not gonna happen.  Too much money for working on one TV.  I haven't finalized the deal on the analyst yet, but I'm working on it.  I appreciate you guys' input.  I'd never get this project done without you!   :) :)


The power supply on this chassis has a voltage doubler circuit.  There is a 130uf @350 volt electrolytic cap for the voltage doubler.  It is housed in a cardboard "can".  It appears, if I'm reading the schematic properly, that this cap connects positive to the output of the rectifiers, and negative to the positive of the next filter cap, a 100uf @ 350 volt electrolytic.  I have run the wires and somewhat understand its purpose.  I'm not 100% sure how to connect the 130uf cap physically.  I don't know why I'm having so much  trouble getting my head around this thing..... :-[ ;)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on April 12, 2019, 10:14:35 PM
           I agree Gregg, those voltage doubler circuits "just don't look right" somehow. Plus I'm not even sure if it qualifies as a single full wave rectifier, with a filter cap charge every 1/120 sec or two half wave circuits, each one charged every 1/60 sec with the two half wave outputs placed in series. And does one cap pass the entire AC waveform and the other one only half ?
          I've seen several doubler arrangements. One floats the AC winding, has the diodes connected back to back, and the caps connected in series. In another circuit, one side of the AC winding goes to ground, the other side goes through a cap to the junction of the two diodes in series, and the other cap goes from the other side of the diode to ground and that one has the full doubled voltage on it.
          I wonder if the phase detector diode, supposedly selenium, has several selenium units stacked in series, like the finned square jobs seen in small radio power supplies. If so no wonder they don't measure good with a 1.5 volt battery in a standard ohmmeter circuit. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on April 13, 2019, 02:59:49 PM
"Pluge pattern".  (Not a mis-spell).  More TV nomenclature I know nothing about.  Basically, this is concerning setting the gray scale on a monitor, mostly color monitors.  I learned something...... :-[



I Googled it.  I can't seem to get the link to download.  There is a pattern one can download, and, presumably feed it to your TV via an Analyzer?  Or maybe even your phone if you knew how..... ;)   An Analyzer has a bar pattern.  Why wouldn't that work as well?


I don't believe this will benefit my TV chassis, but it might be fun to experiment with.


Why am I posting all those small letters? 


Try again:


https://whatis.techtarget.com/definition/PLUGE-pattern-picture-line-up-generation-equipment-pattern (https://whatis.techtarget.com/definition/PLUGE-pattern-picture-line-up-generation-equipment-pattern)


The pattern on an Analyst WILL work as well as one you download.   :)


Although this discussion was about color monitors, why wouldn't these gray bars diagnose possible weak black and white CRT conditions?  Would not the black and white tend to smear or wash together if you had a weak CRT?  And would not a good CRT make the black and gray scales sharp and detailed?  Experts?   ;) ;) :) :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on April 14, 2019, 09:28:24 AM
        The early color CRTs (and maybe later ones too, I only know about the old 50s and 60s stuff) had the most efficient blue, "cyan"  (greenish) and red phosphors they could formulate but apparently their efficiencies were horribly different with red being much weaker than the other two. So the beam currents were grossly different in a black and white picture where each phosphor had to emit the proper amount of light to make a white screen with no tinting. The blending had to hold steady all the way from a total white screen down the grey scale to dark grey and finally total black. The low light level tracking adjustments were usually called red, blue and green screen and varied the 3 color gun screens individually. The high light level tracking adjustments were usually called drive and often were only two adjustments because red drive was always internally set at maximum as  the red phosphor was so inefficient. (at least on the old RCA we had, CTC10C. )
   The test pattern usually had large vertical bars that varied from black through grey to total white, sort of like the color bar pattern but only black and white. A black and white set didn't have any need for the grey bars except to make sure it could reproduce the shades of grey instead or a washed out picture, as therer was nothing to track
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on April 14, 2019, 07:52:15 PM
             Y)ou could still have a black and white tv that has grey scale tracking problems, and that would be a picture that was harsh with dark and white and little grey in between. If the TV RF and IF circuits were overloaded by a strong nearby signal, with poor AGC circuits or if the video amplifier had the contrast control severely misadjusted the picture could have a glare like quality. A lot of transformerless  tv chassis with only a half wave rectifier and a 130 Volt DC B+ seemed to be more prone to bad grey scale, possibly because of picture tube voltages being on the marginal side. If you take a tv set with a good picture and variac it down to 95 volts AC you will see just that kind of decay in the picture. It starts to look like one of the later Muntz tvs with only 12 tubes in the entire set.
          A lot of old style "target" test patterns had converging finely spaced lines that tapered in from the top, bottom and sides, all toward the center. You could tell how wide the bandwidth was of the IF and video amp circuits by how close to the center the lines could converge and still stay separated instead of blending to grey. You could tell how well the two halves of the picture would interlace by how well the horizontal lines stayed separated as they converged to the center. the converging circular bar sections have shadings of intensity from dark black to total white. They usually have the diode detector hooked up so that black is full negative DC and white is closer to ground. That way static and impulse noise will only drive the CRT  to blacker than black, or beam current cutoff. If the polarity was the other way, impulses would make noticable "sparkles" that early FM modulated satellite TV pictures used to have. The rt would be modulated cutoff and extra bright by noise pulses.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on April 14, 2019, 09:22:31 PM
My understanding is that the B&K TV analyzers have that test pattern you describe with the fine lines converging to the center.  Some TV restorers also like the Indian head test pattern.  What advantage was there to the Indian head pattern or was it a matter of preference?


When I worked for Mr. Wells in his Zenith-only TV repair shop, the test pattern came on TV, via Channel 10, from 5am to 7am every morning.  It was a big deal to be ready for that test pattern.  Mr. Wells would do his convergence setups and that during the time the test pattern was on.  He did not use a generator, preferring the real McCoy. 


I have a friend whose dad was responsible for the development of red phosphor for color picture tubes for RCA.  They never had a TV at home.  His dad also had an affinity for '41 Fords.



Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on April 15, 2019, 01:31:08 AM
     I think the Indian head test pattern was the RCA overlay whatever that means, that's how it's described on p.66 of Jan 1950 radio eleectronic news magazine, if I have the name right. I just saw a pdf download a few days ago and the same issue had illustrations of about 40 or so tv station test patterns, most of which were target style with converging horizontal and vertical lines and grey shaded bars. Maybe a coin collector made the Indian head pattern to look like a 5 cent piece ??
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on April 15, 2019, 09:24:36 AM
              Gregg, I also used to stay up Friday nights in high school waiting for the Saturday morning test patterns which usually came on when the Baltimore station powered up for the day maybe at 5 or 6 AM. Usually, though, I would drift off to sleep just before the station powered up and I would be awakened by the National Anthem playing with a still shot of Fort McHenry (Baltimore was extra proud of the anthem, along with steamed crabs and duckpin bowling).
            I think NBC, being always pushing color, had a color bar test pattern but CBS, resentful that the RCA color standard uprooted the CBS non-compatible color standard, stuck with the target style test pattern that didn't have any special lines for adjustment of color sets. It was a enough of a pain to try and adjust convergence controls on a test pattern but not as maddening as attempting it on a tv shows moving picture. I finally got a used sencore color bar crosshatch generator (about 8 tubes) but it kept losing its internal sync adjustments, so the lines were usually wavy instead of still. I had wound a homemade degaussing coil of about 18 inch diameter out of number  18 or so guage wire, but the turns must've been marginal and the coil got too hot to hold after 20 seconds.
          The moderator of the high school radio club had a used B & K test pattern generator with flying spot scanner and several test pattern that slid into a slot but I never got one though I remember it being the Holy Grail of pattern generators. Then he got this Hickok gadget with about 30 tubes that actually generated the actual NTSC tv signal with correct sync pulses, blanking pulses and whatever the official standard called for. Since the high school I went to was non profit he was allowed to by surplus government stuff at the goverment surplus warehouse and I guess he couldn't resisst all the goodies.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on April 15, 2019, 05:17:36 PM
The B&K generator with the spot scanner and the inserts is what I'm trying to buy.  B&K models 1075, 1076, 1077 and 1077B were the most common.  The "B" version was equipped for solid state sets somehow.  That is the model I'm looking for, since it is the most updated version.  Even those are over 50 years old.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on April 15, 2019, 06:32:20 PM
  I vaguely remember a hinged lid that exposed what looked like a 5" or so oscilloscope CRT and some sort of optics along with a slide in slot with various test pattern on clear plastic sheets. I don't remember ever seeing it used. I assume it only generated black and white video ??
   My grandparents 21" B&W RCA console was my first "real" nostalgia collectible and I still have it. As a teen, I tried to touch up what I thought was the sound IF ratio detector to get rid of a slight buzz in the sound, not realizing I was in the entire wrong row of tuned circuits, and while I was turning one slug after another and hearing no difference, I suddenly looked at the picture and saw horrible smearing and ghosts. Turned out I was in the video IF strip of tuning slugs, not the sound IF.  That was the first of a lifetime of many, many  many things that I should have  .....J U S T  ....... L E F T..... A L O N E  !!!   That and cleaning the dust off the inside of a Philco radio dial glass with a rag soaked in   
  A M M O N I A  !     (I thought that's what you were supposed to use to clean glass windows.  Glass is glass)
   Oh well.  Live and learn.   
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on April 15, 2019, 11:06:00 PM
My understanding is the 1077 models were compatible with color TV sets.  I'm not sure about the 1075 or 1076.  The 1076 and 1077 models are the most common.  All I know about them is what I've read.  The transparent slides are in color as far as I know.  There are a series of four or five slides that are standard equipment with the instrument.  I'm told one can download the Indian head test pattern and make their own transparency of it.  I believe the size used is 3'X4".  What piqued my interest in these things is that I don't have the generators I need for TV diagnosis and repair.  These things are kind of an all-in-one instrument that has several generators built into one unit.  Apparently, most TV shops had some version of the B&K TV Analyst.  I've heard some say they were the bomb, while some say they seldom used one.  I haven't got one yet, so the hunt is still on.  They are not very high priced, but shipping is the killer.


I forget the model number, but the RCA my family had was one of those, about a 14 inch or so, that had a vertical chassis and is hard to work on.  The controls are on the side of the metal cabinet.  The picture tube sticks thru the chassis.  It had vertical problems.  I have not had it on in 25 years I reckon.  It is one of those "someday" projects.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: firedome on April 16, 2019, 08:18:17 AM
At home we had an RCA 21" (I guess) in a mahogany cabinet with a cross-hatch metal grille over the speaker cloth, from around 1951 when we lived in an apartment in Loch Raven Village, then on our houses on Hampton Lane, then off Chas. St Ave, until I left for college in  '68. It was joined by a little 12"? Zenith B&W portable around '66 and the big set went from the LR to the playroom in the basement.  Not until around '70 after they'd moved to NC and I was long gone did they get a new RCA 25" color console in Early American design.

I guess that "deprivation" of not ever having a color set at home in MD has lead to my fascination with all tube-chassis color sets nowadays, Zenith sets in particular. My wife and I got our 1st set, a Zentih B&W 19" portable, in 1971 when we were married. Wish we had kept that one.

Ed - my recollection of network affiliation in Bawlamer is that WBAL was NBC, WJZ was ABC, and WMAR was CBS? ...it's been a long time.  I think they've switched networks around since I left in August  of '68... I miss my O's, crabs, and Natty Boh even now!
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on May 01, 2019, 05:32:32 PM
I made some progress on my TV chassis this afternoon.  Two steps forward and one step back, actually.

I have the chassis back in, wires run semi-neatly, all new RCA tubes populating the chassis.  Ready for the big test as soon as my Kill-A-Watt shows up. 

I have discovered an issue.  Re-reading my notes on this project, I see where I had made a note of a questionable condition wire in the plug to the "picture bulb".  The 27ZP4 has a small pin area for the socket to connect to.  The yellow wire in question was holding by two or three strands, so that is sure to fail.  I will have to drill out the rivets, take the plug apart, be careful to not mess up the wiring going back, then fix that broken wire and resolder the connection.  I don't believe it will be too bad of a job, I just need to document well with pictures before I pull that socket apart.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on May 14, 2019, 04:23:11 PM
I finally got an afternoon to spend with my Stereo Theater project.  I took the plug on the "picture bulb" apart to fix the now broken yellow wire.  This Mickey Mouse contraption is not one of Magnavox's better ideas.  The connections were crimped and not soldered.  That is a disaster waiting to happen.  I removed all the connections in the CRT plug and resoldered them.  I put it all back together, held temporarily with small wire ties until I can get to Ace Hardware and buy some teeny tiny bolts.  #2 bolts, maybe smaller.  To be real honest, the wire ties are holding the plug as well as the rivets were, maybe better.  The rivets were loose, which may have been part of the problem.  It's a silly setup any way you look at it.  There is a wafer socket on the CRT, another delicate-looking connection. 

While I was tinkering, I took a closer look at what all the cabinet needs.  I removed the sliding lid over the tuner compartment.  You can see in the pictures how incredibly dirty the finish is on the flat surfaces of the cabinet.  I don't know if this is cooking grease, nicotine, or just what, but it has ruined the finish.  You can see in another picture how it looks being washed with lacquer thinner.  The finish is not totally removed.  The lids are veneered tempered Masonite.  Painted on the edges and underside.  They are in fantastic shape, just dirty.  You can also see a couple shots of the controls with all the yellow nicotine on them.  They should clean up nicely if I am careful with my cleaning chemicals.  I found the missing Magnavox emblem that goes on the tuner controls and a member on this forum has the Magnavox script that goes on the front of the cabinet.

While I was working with the picture tube plug, I had the stereo going on my ST.  This thing, 12" speakers notwithstanding, MAY actually be a better performer than my Symphony.  At least as good.  I really kinda hate to pull it all apart to work on the cabinet.  This thing is a sweetheart.  I'm beginning to wonder if you could power 4" speakers out of a clock radio with a Magnavox 93 series amp and damage drywall.   ::) ;) :)  Although I detest the idea, I can see why the console rapers like that amp so well.  The 93 series is the best Magnavox ever built, and, arguably, the best 15 watt per channel amplifier ever built by anybody.  I'm more impressed with a 93 series every time I use one.   :) :) :) :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on May 14, 2019, 05:30:04 PM
Good work Greg!   I always feels good when progress is being made.   :)

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on May 17, 2019, 11:47:54 AM
I have found that Glance, an industrial-grade window cleaner, will take the gunge off the tuner bezels without damaging the printing.  So that little concern has been handled.   :)

I also have a Magnavox emblem, (not the script) for the one missing on the tuner bezel.  So that has been taken care of.   :)

My next issue, not one that is urgent, but needs to be worked out is the model number and the Run number stickers.  The ones on this cabinet are not complete and are too dark to work with.  None of my Magnavox cabinets have stickers the litho lady can work with.  What I need is for someone out there in Magnavoxland to take a picture of a good model number sticker and a good Run number sticker.  It does not matter what numbers are on them, I just need the complete sticker that is still fairly light and not horribly discolored like mine are.  She can increase or decrease the size, but if they are dark like all mine are, she can't work with them.  And I need to take a good picture of the wiring diagram, pasted on the inside front of the cabinet, so I can reproduce it. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Motorola Minion on May 17, 2019, 02:20:02 PM
I have two cleaners, one called Spray-nine for general grimy crud but it WILL remove printing on aluminum, especially that in attached picture.

The other is white vinegar and it seems to leave this printing alone. Spit and shine works this way too :-[, with lithography being spared.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Harbourmaster on May 20, 2019, 08:08:25 PM
Here are three different model number stickers that the pictures are fairly good.  As you can see they are all slightly different.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on May 20, 2019, 09:39:17 PM
Those are all better than mine, by miles and miles.  Thanks, Ken. 

Three different stickers.  Only Magnavox......

I see that mine might not be in such horrible shape as far as being complete.  The corners are off all those.  That's how the factory did them.  I would have reproduced them perfectly straight, which would have been incorrect.  Those are all infinitely easier to read than mine. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on May 28, 2019, 05:54:39 PM
I have started taking the Stereo Theater apart so I can work with the cabinet.  I found a couple more things I need to do to the TV chassis before I feel comfortable enough to power it up.  With the TV now at the end of the line, I'll try to get the cabinet squared away.  Everything I have found so far is in nice condition, just massively dirty.  Nothing is broken, no wood is split, nothing has ever been moved or taken out except most of the tubes in this instrument.  It does not appear to have otherwise been worked on or serviced. I am taking copious pictures and making detailed notes about the little things I'll need to know for re-assembly.  I started with the safety glass over the picture tube and the mask.  I was dreading those.  It could not have been easier nor more successful.  I'm kinda cleaning as I go, not show quality, but just better.  I have learned that the picture tube should go back into the cabinet first on re-assembly.  My thinking is that Magnavox stood the picture tube up on a board, then built the "Stereo" part around the "Theater".  The picture tube mounting is adjustable at the top to allow the picture tube to fit into the mask without having a gap somewhere.  I pulled the plastic tracks the front doors slide in out of the grooves in the cabinet where they reside.  An ice pick is the bomb for that operation, along with being careful with 60-year-old plastic.  When I spray finish. I may stuff paper in those grooves to make installation of the tracks easier.  There is a piece of brass trim, running the full length of the lower skirt on the front of the cabinet that I have not figured out how to remove.  I'm open to suggestions.  It may have to be taped off and hope for the best.  I have taken lots of pictures.  If you guys are interested in them, I'll try to post them.  I know Chris and Bill like pictures...... ;) :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: 19and41 on May 28, 2019, 06:07:16 PM
Rex likes pictures too.  He is catching up on your saga.  ;D
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on May 28, 2019, 06:27:44 PM
There is a piece of brass trim, running the full length of the lower skirt on the front of the cabinet that I have not figured out how to remove.  I'm open to suggestions.

Is it inserted in a little routed groove?  Is it brass (or brass-plated) metal or brass-colored plastic?  Can you pick it out with your faithful ice pick?  Or drill a hole from behind using some variety of depth control so you don't drill through it, but could tap it out from behind with a small punch of some kind?  Maybe the mask-and-spray option is the easiest....

Years ago I was trying to get the Bourdon tube  temp sensor sensor out of the head of my '38 Buick.  That was before we had an internet and any way to consult on such an issue with people who knew how.  I finally gave up, broke it off, and had the device rebuilt by a guy who had an ad in Hemmings. Now we can solicit ideas and at least have a bunch of options to consider.

Of course, it would work better if you posted a photo of the trim piece....

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on May 28, 2019, 06:37:46 PM
There is no room to get my trusty ice pick on the end of that trim without boogering it all up.  I had actually considered the hole drilling method you suggested.  The hardest part will be getting it started to come out.  It is pressed into two grooves in the cabinet.  I'm hoping that after I get the cabinet turned up on its top, maybe I can figure out a plan to get the trim out. 

Rex, I'll get you guys some pictures.  I'm glad to know you are following this project.   ;) :) :)

You may notice how skillfully I'm sidestepping the "firing up the TV" issue.  Part of my problem is I'm just not ready to do it yet.  I need to be more confident of my TV restoration abilities.   :-[ :-[
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on May 28, 2019, 06:52:47 PM
You are doing just fine Greg!  :) :) :)

Bill

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on May 28, 2019, 08:02:12 PM
Pictures, as promised.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on May 28, 2019, 08:05:45 PM
More pictures.

I'm not sure what the fuzzy stuff was on the picture tube mask, but it was as black as your hat.  It was sticky stuff.  I got it off with Glance, but I don't believe I've ever seen anything like that on a TV set.  How it got in there is another mystery.  There are seals on the brass trim that holds in the safety glass over the picture tube.  It had to come in between the picture tube and the mask.  I posted a picture of the dirt accumulation on top of the picture tube. 

There is a series of small, square bumpers along the ledge where the mask sits.  I thought that was rather Magnavox-ish.  The cabinet looks better in pictures than it does in real life.  I'm piling the parts on a 4'X8' table.  There won't be any room to spare......


Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on May 28, 2019, 08:14:47 PM
These pictures show more of the detail I'm documenting.

I'm still trying to save the wiring diagram.  My next step is to cover it in shipping tape, then try to scrape it off the cabinet with a sharp, single-edge razor blade.  I am taking pictures and making drawings of wiring, just in case.  It is not absolutely vital that it be there, but it would be nice, after going to all this work.  I am "baggin' and taggin'" all the parts as I go along.  I reached out to Radio Daze to see if they would be interested in repopping the wiring diagram label for me, but I have not heard back.

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on May 28, 2019, 09:16:34 PM
These pictures show more of the detail I'm documenting.

I'm still trying to save the wiring diagram.  My next step is to cover it in shipping tape, then try to scrape it off the cabinet with a sharp, single-edge razor blade. 

Why not cut a piece of heavy paper the same size, place that over the diagram to protect it, and then use masking tape to hold that in place while you clean up the cabinet?  In other words, eave the diagram in place, under cover, and work around it.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on May 28, 2019, 09:42:40 PM
The diagram is partially on a speaker board that has to come out.  If there was a way to work around it and leave it alone, that would surely be better.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: 19and41 on May 28, 2019, 10:17:10 PM
Is JPG 031 the problem metalwork?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on May 28, 2019, 10:27:30 PM
Yes, that's it.  The ends of the trim are right up against the wooden upright.  There should be a picture I posted that shows the entire thing.  It is full length of the lower apron on the cabinet.  I bet it would come off rather easily if I could get it started moving.

032 shows what I'm up against with the wiring diagram.  The dark part by the horn has to come out so I can work on the cabinet.

Also notice on picture 004 how dark the safety glass had become.  That would possibly have made me suspect I had a weak picture tube, since it would have dimmed the picture.  I put the edge of the glass in front of the CRT to get an idea how dark it really was.  I trust most of that will wash off.....

I have determined that this cabinet was originally finished in lacquer, hence the reason it needs refinished.  Had this cabinet been finished in the "ten coats of hand-rubbed oil finish" typical of older Magnavox cabinets, all I would have had to do was to clean it well.  I tell myself one minute, I need to redo the lacquer, then the next minute thinking I can do better by using polyurethane.  I sure like the poly over shellac I put on the little Magnavox stereo I did two years ago.  It gets prettier every time I walk by it.  Lacquer will be lots less work.  The cabinet has black grain filler like the little one did.  I would say the grain is semi-filled, not smooth like a piano finish.  The little one was like that as well.  I'm considering using clean grain filler over the dark filler already there to smooth things up a bit.  I've had good results using poly.  I need to make up my mind once and for all before too long...... :-[ ::) ;)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on May 28, 2019, 11:37:03 PM
Some sets used safety glass that was intentionally gray--something about anti-glare.  In fact, of the safety glass I've removed from defunct sets, seems to me most have been gray.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: 19and41 on May 29, 2019, 06:48:06 AM
Yes, that's it.  The ends of the trim are right up against the wooden upright.  There should be a picture I posted that shows the entire thing.  It is full length of the lower apron on the cabinet.  I bet it would come off rather easily if I could get it started moving.

032 shows what I'm up against with the wiring diagram.  The dark part by the horn has to come out so I can work on the cabinet.

Also notice on picture 004 how dark the safety glass had become.  That would possibly have made me suspect I had a weak picture tube, since it would have dimmed the picture.  I put the edge of the glass in front of the CRT to get an idea how dark it really was.  I trust most of that will wash off.....

I have determined that this cabinet was originally finished in lacquer, hence the reason it needs refinished.  Had this cabinet been finished in the "ten coats of hand-rubbed oil finish" typical of older Magnavox cabinets, all I would have had to do was to clean it well.  I tell myself one minute, I need to redo the lacquer, then the next minute thinking I can do better by using polyurethane.  I sure like the poly over shellac I put on the little Magnavox stereo I did two years ago.  It gets prettier every time I walk by it.  Lacquer will be lots less work.  The cabinet has black grain filler like the little one did.  I would say the grain is semi-filled, not smooth like a piano finish.  The little one was like that as well.  I'm considering using clean grain filler over the dark filler already there to smooth things up a bit.  I've had good results using poly.  I need to make up my mind once and for all before too long...... :-[ ::) ;)

If that's the piece, it looks like the piece shown in JPG 001 if the downward portion of it's angle as shown, were put into a horizontal groove with the flange pointing upward. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on May 29, 2019, 07:11:12 AM
At what angle did you take the photo on 031?  It looks like it's upside down?

Bill

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on May 29, 2019, 07:29:20 AM
I'm guessing the piece of trim I'm having a problem with is a "U" shaped piece, set into two grooves, but that is just a guess.  Anybody's guess is as good as mine.  Another guess I have is that this trim is anodized aluminum.  Lacquer thinner and/or acetone may take the brass colored finish off.  I'm making this assumption, since the trim around the safety glass is like that.  It won't be the end of the world having to work around that trim, but I'd rather remove it for the refinishing process.

031 was taken head-on into the junction of where the trim piece meets the upright on the right-hand corner of the cabinet. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: walyfd on May 29, 2019, 11:01:00 AM
Thinner won't remove anodizing.  It's a plating process.  Battery acid will eat into it.  So will road salt. 

You can buff it with white Rouge and a loose buffing wherl.  It looks like the silver is a paint on top of the gold anodized area.  Try car polish.  If you decide to use a buffing wheel, be super careful and mask the painted areas. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on May 29, 2019, 12:33:06 PM
If it is anodizing I may not have a problem.  If it is some kind of finish that is sprayed on, I might ruin it trying to find out what it is.  The finish on the handles on the top sliders is sprayed over pot metal and lacquer thinner takes it off. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on May 29, 2019, 06:18:41 PM
It won't be the end of the world having to work around that trim, but I'd rather remove it for the refinishing process.

When I've been doing partial refinishing--maybe staining and improving damaged areas, repairing veneers--I'll sometimes leave the old finish on undamaged areas.  Then when the damaged areas are ready, I'll put the new final finish over everything--the refinished parts, the undisturbed parts.  If I've matched color tones well, the new topcoat blends it all together nicely.  You might consider not disturbing the original finish around that trim piece, and then just masking it off for the final finish coats.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on May 29, 2019, 06:55:45 PM
I'm thinking about doing something similar to the method you suggest.  Perhaps clean it well, sand lightly, then apply a seal coat of shellac.  Then the finish.  That might work. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on May 29, 2019, 07:09:12 PM
I have come up with a solution to the wiring diagram label situation.  I decided to divide the baby.  I put a couple layers of shipping tape over the label, then cut it in two right where the speaker board meets the cabinet.  If I did this right, I should be able to still use the sticker.  This is not a perfect solution, but it seemed like the simplest at the time. 

I am accumulating quite the pile of parts.  I still need to remove the picture tube.  I need to know how heavy I can expect it to be.  I reckon once I determine that I can lift it safely, I'll just unbolt it, give it a big bear hug and see what happens.  I see guys on YouTube videos tossing CRT's about like a frizbee with no ill effects. 

There is a wire that is stapled to the cabinet under the remote control chassis, runs up under one of the CRT mounting brackets, then back to a square of foil on the rear shelf of the cabinet, the same shelf the TV chassis mounts on, but is not under the chassis.  Does anybody have any idea what the purpose of the wire is.  You can see it in the last two pictures.

I've also read (probably not a good idea  ::) :-[) about a "band" around the face of the CRT that must not be disturbed or it might blow up.  This CRT does not have that band.  All it has is the strap that goes around the CRT to hold it to the mounting brackets.  Taking those brackets loose at the cabinet, then removing the straps at the top is about the only way I can see to get the CRT out.  Am I on the right track here?  This is my first foray into the world of picture tubes.  I'm not sure I'm 100% convinced this is something I should be messing with. :-\

Picture tube apprehension notwithstanding, this has been a fun and straightforward project to this point.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on May 29, 2019, 07:28:29 PM
The radio tuner is the heart of this instrument.  Everything runs thru the radio tuner.  It is buried and connected to wiring galore.  It is also heavy and cumbersome to handle.  You need to hold the tuner with one hand and remove bolts with the other.  Or you need a willing accomplice. 

The method used to mount the tuner bezel into the cabinet is engineering at its finest.  They provide little brackets that suspend the cabinet back while you are installing or removing the bolts that hold the back on.  I suppose this is so there is no chance of necking the tube while you fiddle with the back.  I wonder how they got this past the bean counters who were working overtime in 1962. 

Magnavox also provided logical and usable connecting devices for radio, TV and external speakers on this instrument.  Instead of having all the connections on the cabinet back, these are discreet plastic brackets made to hold the connections.  Notice the TV antenna is used as an FM antenna.  No internal FM antenna is provided.  The FM section in this tuner must be pretty hot, since I pick up several stations with only about a foot of twin lead for an antenna.  AM has its own loopstick antenna, plus a provision for an external antenna.  I plan to built a hotrod back for this like I did my CG, and will include an internal FM antenna.

Notice how Magnavox twisted the upper mounts for the picture tube.  And the cute little wire thingy that holds the wires to the Magnalux sensor off the hot tubes.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on May 29, 2019, 09:15:48 PM
I'm thinking about doing something similar to the method you suggest.  Perhaps clean it well, sand lightly, then apply a seal coat of shellac.  Then the finish.  That might work.

On my Provincial Serenade, to make the top look more respectable and to blend in the small veneer patches, I sprayed some aerosol "brushing lacquer" (c'mon folks, it's not for brushing if it's in a spray can) over the lightly sanded original lacquer.  No shellac required.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on May 29, 2019, 10:53:45 PM
The finish on this cabinet is contaminated with something.  Cigarette smoke, cooking odors/grease, I haven't really figured out just what yet.  It feels sticky or gummy to the touch.  I believe, that low on the cabinet, I can clean the surface well, then spray on a wash coat of shellac as a sealer.  Your suggestion would work fine if I was not working with the gooey stuff.  It's hard to describe.  I believe, though, I'm going to employ some type of shortcut on the lower area of the front of the cabinet if I can't come up with a way to remove the trim. 

I got to wondering how a service technician would replace a picture tube in an "aircraft carrier" back in the day.  He certainly would have a helper.  The way one would replace the picture tube in a regular TV would be to lay the TV on its face, unbolt the picture tube and let it lay on the floor, then lift the TV cabinet off the picture tube.  This cabinet is too large to do that, and too heavy.  If I get a helper, I believe this one can come out the front.  There is plenty of room.  The weight will be the issue.  I'm afraid I can't control the picture tube safely if I try to get it out from the front by myself.  I read the warning on the picture tube, "High vacuum glass picture tube is dangerous to handle.  Refer service to qualified personnel", which I ain't.   :-[ ::)

The brackets that hold the picture tube on the bottom are the same, just reversed side to side.  The right one has one bolt in front, two in the rear.  The left is reversed, two in front, one in rear.  The holes in the shelf it sits on appear to be larger than the bolts (screws, actually) to allow for some adjustment so the CRT will fit the mask.  Maybe 1/4 inch total.  Adjustment at the top is more generous.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: 19and41 on May 30, 2019, 07:26:00 AM
Maybe it would be prudent to enlist a helper when It comes time to remove the tube.  There are warnings on the tube as there is the possibility that it could be damaged.  The principal source of damage is the breaking of the evacuation stem at the rear of the tube.  Bear in mind though, the tubes were handled and shipped and stored for substantial periods before they were secured in a working chassis and can abide careful handling without any sharp impacts.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on May 30, 2019, 08:13:10 AM
Good advice well taken!   :)

Ron the Refinisher may be enlisted to help with the project. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: 19and41 on May 30, 2019, 09:38:43 AM
One other piece of hard won advice, take care with the CRT's connector.  The whole assembly can become brittle with heat and time.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on May 30, 2019, 10:50:17 PM
The CRT plug has already fallen apart on this one.  The connections were crimped instead of being soldered.  One looked rather weak, and, of course, broke.  So I took the socket apart and soldered all the connections. 

I got the TV tuner out this morning and found a problem I had already suspected existed.  I believe there is a knob that goes under the tuning knob that is missing.  It's job would be to turn the channel indicator and to hold the fine tuning knob down so it meshes with the gears in the tuner.  I can turn the tuner to change the channels, I just don't know what channel I have selected.  If the tuner works, this is no big deal.  I can connect the TV analyzer and the screen will produce an image when I get to Channel 3.  If the tuner does not work, then I have to get creative.  I do not have any information on what or if I'm missing anything.  The speaker switch has a pal nut on it, so it comes out with the bezel and the crossover network and associated wiring in one chunk.  The plan is to remove the picture tube on Saturday morning.  That's when my help is available. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Motorola Minion on May 31, 2019, 01:35:32 PM
Backing up a page or two, I have a picture which shows the knob you have. It has tabs that spin the internal number wheel, and it holds the FT knob. Those knobs usually were in good condition till the end.   

Common for just about all Magnavox TV consoles and table models using the "white window" up through 1968, when it changed only slightly and continued to be used another 5 years. :P 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on May 31, 2019, 11:11:02 PM
My white window is on top, yours is under the channel selector knob.  Your channel selector knob looks like mine.  My channel knob has two slotted tabs on the inner rim that are obviously supposed to contact something else.  My channel wheel just spins freely.  I can see there is something silver colored inside and under the channel knob on yours.  I believe that "something" is what I'm missing.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 02, 2019, 08:06:52 AM
Now that the missing knob mystery has been solved, I have been planning the next step.  I like to investigate certain aspects of the project and "get to know" what I'm working with.  I wondered why this Stereo Theater only had 12" speakers instead of the more familiar 15's.  The room for a 15" speaker on the tuner end of the cabinet is non-existent.  It would fit okay on the changer end, but certainly not on the other end.  I also found that the radio and TV tuner bezels were in the cabinet before the finish was applied.  I had to remove a cabinet brace to be able to remove the TV tuner bezel.  1962 might be the first year for the infamous Magnavox pal nuts.  There is one on the speaker switch.  I have temporarily solved the messy wiring I gripe so much about.  I don't see how I can improve on it much when I put everything back into the cabinet.  Apparently Magnavox made the wiring sloppy for a reason, now lost to history.  The wires are too short in many cases to improve matters much.  At least, this time when I go back, I will have CLEAN sloppy wiring.  I am trying to find a schematic for the speaker crossover networks in this thing.  There are a couple components I am not familiar with that I would like to identify and be able to test as needed. 

I don't understand how someone could buy one of these things, then gut the cabinet to sell the amp, then toss the rest.  These things are miraculous in how they are built, but still manage to work.  I can understand why guys on old radio forums who worked with these things back in the day are glad to see them not around anymore.  This thing would be a nightmare if it were located on a third floor flat in Brooklyn and I had just found it had a bad picture tube!  How would one ever put this cabinet on its face, with all the components still in the cabinet, to replace the picture tube?  You would need four stout people to manage it.  You would need a football field of space to wrestle it around.  And carrying it down three flights of stairs so you could take it to the shop would be another nightmare.  I bet they must have charged $25 or $30 labor to change a picture tube in one of these things back then.  That might have been half a week's wages.   :-\ ::) ;)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 02, 2019, 12:20:18 PM
Other than the screws in the picture tube brackets, I have taken every screw out of this thing that allows something to fall off.  This is a true "every nut and bolt" restoration.  Every wire, every screw, every bolt and nut. 

Next process is to start removing the old finish.  I don't want to use stripper.  I will use a concoction of 50/50 lacquer thinner and acetone to wash the finish off.  Once that is done, I'll sand flat surfaces with 320 grit, non-flat surfaces with 0000 steel wool.  Then it gets a seal coat of shellac.  Then I'll see what the stain looks like.  I know the bottom edge of the cabinet, under the sliding doors, is lighter than the rest.  It will need the stain touched up for sure.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 03, 2019, 05:44:01 PM
I have the finish washed off the top, sliding lids and one end.  This is going to be a pretty cabinet, much like my 616, only 18 inches longer.  Both are "NWAL", natural walnut finish.  Some parts of the cabinet are naturally lighter than others.  I'll need to use black grain filler on the top edges of the cabinet.  I've been using 0000 steel wool and my lacquer thinner/acetone mixture and have been having good results. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Harbourmaster on June 03, 2019, 06:54:33 PM
That 50/50 mix of Lacquer thinner and Acetone works great on most older furniture finishes, I use it a lot.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on June 03, 2019, 08:35:29 PM
Sounds like it would make you woozy from the fumes.  And people would be well advised not to use it in places with pilot lights.  My shop heater is a natural gas convection device--no fan--and the air intake is from outside, concentric with the exhaust flue.  That means that the pilot light is not connected with the inside air and I can spill solvents all over without igniting the fumes.

On the upside, you don't have the cancer risk associated with methylene chloride based strippers.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 03, 2019, 09:37:22 PM
Besides cancer, stripper will take off the stain and grain filler.  This stuff I use will take off the finish, but won't hurt stain or grain filler.  If you keep soaking the wood, stain will start coming off, so you need to be careful not to get it too wet.  I use cross-ventilation, so the fumes don't bother me.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 05, 2019, 01:11:59 PM
I have the finish off most of the cabinet.  Only one end left to do, and some detail work inside the end compartments.  I have not used a quart of the lacquer thinner/acetone mixture on this huge cabinet.  I typically use that much on the top.  The finish just falls off.  I'm using a toothbrush to get into all the nooks and crevices, of which there are plenty, all full of dirt.  I'm debating whether to use lacquer or polyurethane on this cabinet.  Lacquer is a lot easier, less work, less dry time, less cure time, but I'm just not impressed with how easy it comes off.  Refinishing this cabinet is a lot of work.  I'm not concerned about the purists, they can squeal all they'd care to.  I want the best, most durable finish I can muster after going to all this work.  Our cats would have lacquer ruined in 15 minutes..... ::) :-[ :-\
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 05, 2019, 05:31:35 PM
I worked three hours this afternoon cleaning the area around where the tuner bezels go.  There are three steps where the sliding lid fits.  This is quite the challenge, getting this area clean for a new finish.  This has taken longer than the rest of the cabinet did.  And I'm not done yet.  The TV tuner bezel will retain some of its nicotine-induced patina.  I don't intend to press my luck.  I have used Glance, alcohol and vinegar on it and my fear is the letters around the external speaker switch are in danger.  So I'm stopping while I'm ahead.  Patina in this area will be part of its history.  This panel is tempered Masonite with silver paint and letters applied.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 06, 2019, 10:32:03 AM
I have more general pictures I thought might be of interest.

In the last picture, my trusty therapy dog, Bentley, my constant companion, has cornered a turtle, his favorite critter in the whole world.   :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on June 06, 2019, 11:56:14 AM
Great work!  I love the shade/color of the wood.  That is beautiful walnut. 

Bentley looks like he is having fun.  Was this before or after the buggy ride?  :) :)

Bill

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 06, 2019, 02:30:44 PM
During a buggy ride.  He bailed off the buggy like he had been shot.  He can spot a turtle quite a ways off.  He LOVES turtles.  He's gonna wear out his barker on turtles... ::)

The cabinet is three shades lighter will all that black stuff off of it.  Ron the Refinisher has made the determination that he is going to try out his new poly over shellac procedure he uses on gun stocks on this cabinet.  He has found a way to knock down the shine without all the work I went to on the last Magnavox console I refinished.  Now the hunt is on for some extremely black grille cloth.  It needs to be ultra-black, but I'm not paying $50 a yard, either.  I want it to have a more coarse texture than burlap without looking like a guitar amp.  I found some I liked on the Internet, but it would cost almost $100 to get enough to cover everything.  I need to be in for a quarter of that, or less.   ::) :-[ :'( :)

If anyone wonders why I don't put the original stuff back, that's because I have no idea what "original" was.  This thing has two different kinds of grille cloth on it, and they are both ugly.  My wife generally hates Magnavox grille cloth, with a few exceptions.  She thinks the grille cloth on my CG looks like a shower curtain.  She likes the cloth on the Imperial and on the Symphony.  And the little one I did with black burlap. 

You won't recognize this thing the next time you see it, Bill.  Remember how we remarked how easy this cabinet rolled and how good of casters it must have?  It only has three that have wheels!  One caster has no wheel at all.  Wonder how easy it will roll with all four wheels?   :-\

Harbor Freight has casters the right size I believe I'll try.  They are alleged to roll easily on hard surfaces or carpet.  The big Magnavox instruments don't like to roll on carpet, and not very well on tile. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Harbourmaster on June 06, 2019, 03:40:21 PM
THAT is not a turtle!


Buy whatever cheap grill cloth suits your fancy and some black RIT fabric dye and make it as dark as you like.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on June 06, 2019, 05:32:51 PM
I have more general pictures I thought might be of interest.

In the last picture, my trusty therapy dog, Bentley, my constant companion, has cornered a turtle, his favorite critter in the whole world.   :)

I'll bet the turtle doesn't reciprocate the affection....

Public radio news last night or the night before had a piece on turtle-sniffing dogs in Iowa.  They're seeking out a rare species for breeding & protection. Amazing what dogs can do with their noses.  Here's a link:
https://www.npr.org/2019/06/05/729973589/good-girl-these-dogs-are-helping-save-habitats-by-finding-rare-turtles

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 06, 2019, 08:55:40 PM
We have the picture tube out of the cabinet.  That wasn't a bad job.  It literally fell out.  Seriously.  I never thought to check to see how tight the band was that holds the picture tube to the brackets.  If we had tipped the cabinet before we had it on the blankets......... :-[

There was no harm done and I learned something.  Now I have to remove the brackets from the cabinet and put them back on the picture tube.  The picture tube sits on rubber pads inside the brackets.  These pads have compressed over the years so much that the band was really loose.  I never thought about something like that. 

Next step is to remove the Magnalux sensor.  I got the pilot light jewel out.  And I need to replace the casters while I have them so accessible.  I plan to put resin on the bottom of the particle board panels to stabilize them.  And I'll finish cleaning the underside surfaces of the cabinet and tape off the piece of trim I've been concerned about.  I'd like to be ready for finish in two weeks.

A 27ZP4 picture tube might weigh 20 pounds.  I was surprised how light it was.  I was under the impression you needed a forklift to lift one. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on June 07, 2019, 07:01:56 AM
I'm glad that step is done and it was not difficult.  :)   So, are you saying, when you laid the ST on it's front the picture tube fell out of the strap?  If that's the case, it could have easily fell backwards when moving, or jiggling going down the road.  That would have caused the neck to break.  :( :( :(   B&W tubes are not all that heavy.  Color tubes are a different story.

It won't be long and you will have a refinished Magnavox Stereo Theater cabinet, and that will be a big step out of the way.  :) :) :)   Keep up the good work!

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 07, 2019, 11:49:31 AM
We didn't have to put it all the way to the floor.  The cabinet might have been tilted to a 45 degrees before the picture tube fell out.  We were well prepared, which was a good thing.  It likely would not have fallen backwards, due to the metal TV chassis.  The mask would hold it in front, then the safety glass, so I would not be worried about it coming out with all the stuff in the cabinet.  It was not safe sitting on the bench like it was, in my opinion.  I'll watch that from now on.  I don't know how tight is too tight.   ::)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on June 07, 2019, 02:24:58 PM
The important thing, it did not break.  ;) ;) :) :)  The metal band with the bolt/screws should be tight.  Is there another metal band/strap around the picture tube, one that's still there?  It should be much easier putting it back in.  Each day is a closer day to a finished Stereo Theater.  :) :)

Bill 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: walyfd on June 07, 2019, 04:53:10 PM
I've been following this from " I gotta get one!" To "I got one!" to now...  and I can relate since I got my '62 Fleetwood...  more parts than you can count and how did HUMANS design and assemble all this...

Anyway, if you're looking for a grill cloth that goes with just about anything, consider cane.  I have it on the Fisher and redid a set of Bozak Tempos with it and it doesn't scream "I'M A SPEAKER".

Great job so far. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on June 07, 2019, 04:57:11 PM
Source of cane?  I was trying to remember that word because that's what my little "Home-Mark" device looks like it had, judging from the fringe that's left.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: walyfd on June 07, 2019, 05:50:21 PM
https://woodworker.com/search.html?search=Caning&searchmode=2

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on June 07, 2019, 08:54:50 PM
The old '51 (+/-) Magnavox has a cane-like grille cloth, backed with some open-weave black cloth to give visual opacity.  It looks like the square weave in the link.  And the Home-Mark had the same arrangement, although the "cane" may have been some synthetic substance. 

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 08, 2019, 07:28:24 AM
I like the look of cane, and I appreciate the suggestion.  Something to consider.   :)

This is has been the most ambitious restoration/renovation I have ever undertaken in my life.  I restored a '56 Packard one time that had 1200 pounds of mud-dauber nests in it, but this is more ambitious yet than that.  I go over pictures of this project from time to time to see the progress, and to plot the re-assembly.  I am considering buying hanks of wire in blue, green, black, brown, white, gray and purple to try and fix some of the wiring mess.  Some wires, like the main cable from the radio tuner to the MPX adapter are way too long.  The speaker wires, from the external speaker switch to the crossover network are way too short.  It would be beneficial in several ways to have the mess under the radio tuner sorted.

There is no band around the picture tube.  It looks to me like the front of the picture tube is about an inch thick.  The only band there is would the one NOT holding the picture tube in.   ;) ::)

The journey from "I gotta have one" to "I got one!" to now has been one of the most rewarding and fun ever.  Several individuals have made contributions, both great and small, all vital, all greatly appreciated, to make this project go as far as it has.  These old combinations, Stereo Theaters, Home Theaters, or whatever they are called, from whatever manufacturer you can name, deserve a better fate than to have their audio amps robbed, and the rest set to the curb.  For Magnavox to have the sheer audacity to build one of these with off-the-shelf parts, with a 100% hardwood cabinet and be able to actually sell them when they were priced about what a good used car would cost, is a miracle in itself.  Something like that will never be built again.  TV repairmen hated these things, and I can understand why.  They are huge, heavy, expensive to fix and nearly 100% obsolete by today's standards.  This is the LeSabre sedan of Magnavox.  We have to remember this was the way console stereos of any kind were less than ten years ago....

As a side note, I have never seen a set of casters on anything as beat up as the ones on this ST cabinet are.  How do casters get beat up?  One has its wheel totally gone, one has half a wheel, and the others have chunks missing in their wheels.  This ain't a skateboard, for pity's sake.   ::)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 08, 2019, 01:47:57 PM
I've spent some time this morning figuring out what size casters I need.  These casters are on 1 1/2 inch blocks, so I believe the blocks can go to leave room for bigger wheels.  I found one of the mountings for the casters on one end is broken free of the particle board it's glued to.  I'll drill the mounting and use a couple construction screws to stabilize it.  I'll try to take some pictures so this makes sense.  The bottom of this cabinet has had a hard life.  I wondered if something extremely heavy had been sitting on top of the cabinet.  I don't see any evidence of that.  I can use casters that are 3 1/2 inches, give or take, and have the same height on the cabinet I have now.  The 3 1/2 inches is measuring from the top of the mounting plate to the bottom of the wheel.  The casters on here now are the kind that has the stud that goes up into a metal piece.  I will need to offset larger wheels slightly so they will have room to turn.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 09, 2019, 10:49:53 AM
I was looking at the picture tube I removed.  I noticed a couple bent pins.  I noticed a couple of scratches on one of the inner beams in the cabinet.  When the tube fell out of the brackets, it contacted the wood.  I came THIS CLOSE to necking that picture tube.  Anybody working on a Magnavox or any other TV with a strap around the picture tube should check that strap to make sure it is snug before trying to remove the picture tube, whatever method you're using.  I was going to do it from the front, until several members cautioned against that.  So I tried it the proper way, laying the cabinet on its front, and almost had a disaster anyway.  I simply was not aware of that danger.  Even the ones with the picture tube and chassis that slide out together may have this issue.  Better safe than sorry.  This is my first TV project and I'm leaning a LOT.  One thing I've learned is to check the strap holding the CRT in place before you remove it and the tube together. :-[
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 11, 2019, 08:26:50 PM
Today was kind of a mop-up day on the old ST.  I removed the Magnalux sensor, the last thing left in the cabinet.  That is not a huge deal, but you should be careful with the little red jewel in front of the sensor.  It is held in by a Jesus clip and will break if you get too aggressive.  I am still not satisfied with how the finish is coming off in the end compartments, so they will need more work.  The end the tuners were on was as dirty as I've ever seen a cabinet.  I had to mask off the paint in the changer compartment.  It cleaned up real nice and I don't want to have to redo it if I can avoid it.  I have removed the old casters and have installed new 3" x 7/8" casters that I got on sale at Harbor Freight.  They are semi-soft rubber and roll easier than the old hard plastic ones that were on there.  I took pictures of the old casters and will post pictures as soon as I get them downloaded.  We are going to reinforce the particle board floor pieces with fiberglass resin instead of trying to replace them.  The glue is allowing some of the fibers in the particle board to flake off, but the panels do not appear to be weakened.  The resin will reinforce them and keep them from shedding.  I will paint the panels on the inside with dark brown paint.  I almost have the entire inside of the cabinet coated with two coats of shellac.  This is a tedious job.  The casters raised the cabinet legs about 1/2 inch higher than they were.  This will help if it is on carpet, as the old wheels allowed the legs to drag on the carpet.  I like these wheels well enough I feel it might be a good stunt to put a set on the Concert Grand and on the Imperial.  The casters are mounted on a piece of 2" X 3" dimensional-cut hardwood, probably poplar.  They run the length of the ends of the cabinet.  They are held in by what I call a trunion, a bolt with a flat top that is screwed to a filling in the wood.  The ends are glued to the particle board.  The ends have broken loose, so the mounting board moves.  I stabilized that board with six, 2 1/2" construction screws, drilled and driven in from the top.  Next up is stain and grain fill plus a couple seal coats of shellac that I believe I'll brush on.  My goal is to be ready for Ron the Refinisher to spray the new finish in a week or so.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on June 11, 2019, 09:02:01 PM
Polyester or epoxy resin?  I'm generally partial to epoxies because they are stronger--more adhesive.  The town where my Chevy and the Home-Mark stereo live is Bay City, MI, also home of Gougeon Bros. epoxies.  Two of the  brothers were early innovators in the use of epoxies in boatbuilding and they gradually transitioned from being a company that built boats with epoxies to one that sold epoxies and built a few boats in the off-hours.  They have an excellent web site with information on the use of epoxies and strong technical support. 

https://www.westsystem.com/company/

Once when I had to repair a laminated mahogany part for my boat after it was hit and started delaminating, they recommended using their slow hardener and warming the mixed product to a specific temp in a double boiler to make it less viscous and more penetrating.  They don't recommend thinning with solvents because it affects strength.

The company is now employee-owned.  Its a good organization, with lots of R&D and a customer focus.  No, I'm not an employee, but I know what high quality people the brothers were and the standards they set.  My boats have their epoxies all over.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 11, 2019, 10:09:51 PM
We are using the same stuff we used on the fiberglass body of our old golf cart I redid a couple years ago.  I'm guessing polyester resin, but I don't know that.  Ron the Refinisher is ramrodding that project. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 12, 2019, 05:01:52 PM
I have some pictures here of the progress of the last couple days.  I have the cabinet in stain at this point.  I have done all I can do.  Next is a wash coat of shellac then sand.  Then probably some grain filling, particularly on the top edge of the cabinet and the ledge under the picture tube.  Those places took a beating when I cleaned the cabinet.  After grain filling, another couple light coats of shellac, sanded to further smooth things out, particularly the top of the cabinet.  The cabinet is natural walnut finish, which is only semi-grain filled.  You'll see how I reinforced the wheels mountings and the various little tasks I had to accomplish.  I'm happy with the project so far.  If it all goes this well, we'll be done in less time than I anticipated.

I am cleaning the shelves where the TV chassis and the picture tube sit.  I'm going to stain and finish them so they will look better.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 12, 2019, 05:07:06 PM
Here are a few more pictures.

There is a single uninsulated wire that is stapled under the remote control chassis, up to under one of the mounting brackets for the picture tube, back to a square of aluminum foil under where the TV chassis sits.  What this is for I have no idea, but it must be some type of shield of some kind, maybe to prevent some kind of interference?  I have not bothered it, and plan to reproduce the aluminum foil sheet since it is ragged looking.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on June 12, 2019, 07:00:00 PM
It's looking good Greg!  With each day, you are one step closer to the finish line.  ;) :)

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on June 12, 2019, 07:57:40 PM
I am cleaning the shelves where the TV chassis and the picture tube sit.  I'm going to stain and finish them so they will look better.

And it's in a place where nobody will generally see it.  But doing things not because they're visible, but because you want it to be right, is what we call craftsmanship.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Harbourmaster on June 12, 2019, 08:04:39 PM
Those casters look to be a big improvement over the originals.


As far as the particle board goes, if it were me I think I would be inclined to pull off the little angle brace blocks and cut a piece of 1/2" or 5/8" plywood to fit nice and snug... then slather it up real good with glue, clamp it up tight and double up the whole base.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 12, 2019, 09:59:57 PM
Thanks, Ken, for the kind words.  My goal is to get this done in three years.  I have three weeks to go on my first year.  I appreciate everyone's interest.   :)

I had thought about completely replacing the bottom panels.  I chickened out.  Those little braces for that front apron are happy where they are.  The lower apron is load bearing.  Your suggestion is well-taken.  I have used epoxy in the past in a similar situation with good results.  I'm going to try epoxy first and see where that gets me.  The wheels are a good replacement.  I believe my Concert Grand and Imperial are going to get a set of those. 

Chris, those two shelves looked like they had been holding a Cummins diesel rather than a TV set.  I can't put this much work into something then return the TV to such a shabby environment. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 13, 2019, 09:58:02 AM
While I am waiting on Ron the Refinisher to do whatever it is he is going to do, I am going to work on how to eliminate some of the rat's nest of wiring when all the components go back into the cabinet.  Thanks to Bill and a brilliant idea we came up with, the main mess under the tuner involves the wires from the external speaker switch to the crossover network board.  The method I'm considering is to get some appropriately colored wire and make extensions to the existing wiring.  I'll plug the extensions without hacking the original wiring.  The wires to the speakers on the tuner end are part of that extension plan as well.  The wires to the changer and TV chassis can be routed together straight across to the upright.  The Multiplex adapter and remote control chassis wiring can be routed along side the bass speaker under the tuner.  I'll use longer cables for the Multiplex adapter to tuner and route it toward the rear of the cabinet.  The plan is to create a hotrod back panel for the cabinet like I did on the Concert Grand so most of the electronics will show.  There is so much stuff crammed into this cabinet and Magnavox put tube shields on too many tubes to suit me.  The tuner and MPX tubes have lots of shields.  This keeps the tubes from glowing as much.  I realize this is a petty gripe, but I like to see things sparkle when they run.  The Concert Grand with the open back I made for it is the prettiest contraption when it runs I have ever seen.   :) :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on June 14, 2019, 02:58:58 PM
As to those tube shields... bear in mind that no company is going to throw in extra parts just for the hell of it.  If they put a shield on, there was probably some RF-related reason for doing so. ( Now I'll admit that there was a time when some companies threw in extra tubes or transistors, but that was at a time when people evaluated quality by tube or transistor count.  Some used faulty transistors as diodes but still counted them.  But that was all done to increase profit.  I've never heard anybody boast, "My device has more tube shields than your does.")

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: amglow on June 14, 2019, 08:58:36 PM
I do not know if it is the case here, but in the ham radio community there discussions about tube shields helping to dissipate heat from the tube envelope to increase performance and prolong tube life.  Granted, they are more specifically designed for heat dissipation than what we see in the consumer market.  Look up "IERC tube shield" and you will find some articles explaining their use in military receivers of the mid-fifties, such as the Collins R-390a receiver.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 17, 2019, 08:45:03 AM
Ron got the epoxy on the bottom of the cabinet.  That looks nice enough to just leave as is.  Next up is to finish applying shellac to the inside of the cabinet with it flopped on its top and to touch up spots I may have missed.  Then, if it ever quits raining, we'll be ready for finish.  The roof on my "oak tree spray booth" leaks when it rains.   ;)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 17, 2019, 11:51:48 AM
My new friend, Mr. Google found this grille cloth that is a top contender.  Maybe not THE one, but close.....

https://www.amazon.com/Parts-Express-Speaker-Grill-Cloth/dp/B07MVH76X2/ref=asc_df_B07MVH76X2/?tag=bingshoppinga-20&linkCode=df0&hvadid={creative}&hvpos={adposition}&hvnetw=o&hvrand={random}&hvpone=&hvptwo=&hvqmt=e&hvdev=c&hvdvcmdl={devicemodel}&hvlocint=&hvlocphy=&hvtargid=pla-4584276299800494&psc=1

This should get all I need for $20. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 17, 2019, 05:52:29 PM
I put a wash coat of shellac on the lids and top so I could sand and level a bit.  I found a faint, 4" water ring I had not noticed.  I believe black grain filler will hide it.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 19, 2019, 05:34:52 PM
Water ring has been taken care of.  Grain filling done.  Shellac done.  Sanding done.  I may finally be ready for a finish.  Weather is the issue now. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on June 19, 2019, 08:53:18 PM
Weather is the issue now.

Damn, ain't that the truth. It's now past mid-June and we're operating on a ratio of one sunny day to 5 cool, gray, and/or rainy ones.  This is crazy.  The Great Lakes are very close to record high levels because of all the precipitation.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on June 21, 2019, 09:09:44 AM
Chris...

You must be on the right side of things up there in TC.  Down here in little ole' Hart, we are seeing the sun once in about 10 days.  :) :) :) :) :) :) :) :)

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 21, 2019, 09:42:57 AM
The weather guessers say highs in the 90's with humidity to match thru the weekend, then rain Sunday evening into Monday.  The plan right now is to try and shoot this thing Tuesday evening.  We'll see....... ::) :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on June 22, 2019, 06:17:31 AM
Greg!

Good thoughts going your way that you will have a clear day for shooting.  :)

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 22, 2019, 12:13:10 PM
The weather guessers got the high humidity forecast spot on.  It is so close here, you can feel it when you breathe.  Our gauge says 95% humidity, and I believe that to be pretty close.  It looks like it could rain any minute. 

I am working on the speaker grilles.  They are tempered Masonite and have been sprayed with glue to retain the grille cloth.  I'm using a single-edged razor to get as much of the old glue off as I can.  Then I'll sand with 80 grit paper to prepare the surface for more glue.  I'll use Elmer's white glue to retain the new cloth.  There were two types of grille cloth on this cabinet from the factory.  I'll bet there were not too many that left the factory like that.  I'll spray the speaker grilles with flat black paint to clean them up a bit. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: firedome on June 22, 2019, 05:33:29 PM
We farther East have also had a fairly damp spring, after a typical mostly gray and chilly to cold winter from late Nov to April, but we're having some spectacular weather right now: sunny, brilliant blue skies, temps in the 70s, and low humidity for Fri/Sat/Sun, ever since a major front went through on Thursday night...  a great way to start summer!
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 24, 2019, 10:25:22 AM
I running a little experiment, so please bear with me.  I'm trying to download a picture of a 417 I have that does not want to be downloaded.  Let's see....

Sorry, it still does not want to work.  Stand by....

What I was trying to do was to document why I have two kinds of grille cloth.  I like delving into these little details.  I'm sure I'm boring everyone else to death.  I have a picture of a really nice 417.  There is a black ink stamping under the amp chassis in mine that says "417", so it is a fair bet that mine started its life as a 417.  The 417 and the 418 are in the same cabinet, with the same picture tube.  The 417 is a five-knobber with six paper cone midrange and tweeters instead of the horns in the 418.  The 418 is also a six-knobber with remote control.  So to change a 417 into a 418, they would have replaced the cone speakers and their mounting boards for the horns and their mounting boards, the radio tuner, the TV tuner, the CRT mask, added the remote chassis.   The bezel around the TV tuner is different.  The 417 has the traditional brown woven grille cloth, while the 418 has a checkered-pattern with a pull for the front doors.  The 417 carries the grille cloth across the front with no pulls.  The grille cloth on the end speakers on mine is definitely what was on the 417.  The front cloth on mine is typical of the 418.  The wiring diagram is pasted partly on the front panel and partly on the cabinet, so there is no doubt this dual-pattern grille cloth setup was from the factory.  What inspector let this by, you reckon?  My plan is to run black grille cloth like the 417 on my 418 and eliminate the door pulls.  They look like they belong on one with a plastic cabinet.  The 417 was available with dark walnut or natural walnut finish, the 418 in natural walnut or ebony finish.  Mine is "NWAL" or natural walnut. 

The pictures I want are stuck in my "Pictures" file in Windows Media Player.  I can't right click the picture, nothing happens.  I can't seem to get them out of Media Player.  I have tried Google.  Nothing.  I'm doing something wrong, not uncommon for me.   ::)

Thank you for your patience.   :)







Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Motorola Minion on June 24, 2019, 01:38:14 PM
Nailing down factory-made modifications, I am reminded of Pontiac restoration details while reading HPP magazine.
Trying to decode a broadcast sheet based on what the car still has left on it, makes fun reading.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 24, 2019, 05:46:26 PM
The ink stamps and the model number and run stickers are the broadcast sheet for a Magnavox stereo.  I am well-documenting these irregularities and will retain the original grille cloth.  By 1962, my thinking is that Magnavox was working on its solid state line and was using up leftovers in the tube line.  Lots of irregularities in 1962 and in the 1963 tube line. 

Today, I painted the speaker boards so I'll be ready for grille cloth.  I'm cleaning components as well.  I have the tuner and MPX adapter along with the attached wiring already done.  I have the 12" woofers cleaned.  I cleaned the horns and applied a coat of car wax on those.  I'm currently working on cleaning the amp chassis.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 24, 2019, 08:56:57 PM
I have some pictures of today's progress.

The first picture shows the two different styles of grille cloth on this thing.  The one on the left was on the front of the cabinet and the sliding doors.  The one on the right was on the end-firing speakers.  The balance of the pictures just show what I was up to today.  I cleaned the nicotine off everything.  I found Go-Jo hand soap, without pumice, worked real good with Scotchbrite to remove the junk.  I used 99% isopropyl alcohol on the remote control chassis to get most of the junk off.  I painted the speaker boards so they will look better.  I did all I felt comfortable with on cleaning the speaker cones.  They are better, but by no means perfect. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on June 24, 2019, 09:19:06 PM
That right-hand grille cloth in the photo looks exactly what would have been in the Hone-Mark console.  Source?

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 24, 2019, 10:25:09 PM
Magnavox, 1962.  That is part of the original grille cloth.  That is also just like what was in my little 616 that I redid.  Would you like some genuine original Magnavox incorrect grille cloth for your little Home Mark console?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on June 24, 2019, 10:48:44 PM
It depends... as I recall from your photos, all the parts were covered in a thick layer of nicotine.  How about the grille cloth?  But it really is pretty close to what was on the H-M.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 24, 2019, 10:58:29 PM
I still have the cloth I removed from the 616.  There was no nicotine on that stereo.  I would think it would need cleaned, but maybe some spray carpet cleaner would do the trick?  I'm not going to use it.  I kept it because....... ;) :)

To be real honest, the grille cloth I took out of the Stereo Theater does not LOOK too bad.  My smeller is not good, so I can't speak to that..... ::)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 25, 2019, 09:25:30 PM
The finish spraying project has been postponed until Saturday next, starting promptly at 8:30AM.  The humidity around here is horrendous.  The humidity is alleged to be lower this weekend.  I attempted to get ready for finish before the humidity cranked up, but, alas it was not to be.

I have plenty to do in the interim.  I reckon I'll have to dynamite the TV tuner to get it apart.  The remote control components are in the way of removing the cover, which is soldered on.  Whose bright idea was that?  Didn't anyone at Magnavox figure I was going to restore this thing 57 years after they built it?  So, I'm going to spritz some contact cleaner and maybe a spritz of the Miracle Elixir, WD-40 into a hole in the cover and wish it well.  Taking that tuner apart to clean it is above my pay grade.  The wire that was spliced around the Molex connector from the TV tuner to the TV chassis appears to be factory.  It is a shield for the wire.  So now I need to fix that. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on June 26, 2019, 07:10:54 AM
While I had your ST in my possession, I never noticed the difference in the grille cloth.  And, wow, there is certainly a difference.  Definitely an oversite by someone.

Lots of work being done in a short amount of time, which makes me think you will have your ST done ahead of schedule.  :) :)

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 26, 2019, 10:56:04 AM
I will have had the ST a year on the 12th of next month.  My goal was to have it done in three years, every nut, bolt, screw, wire, connection, component run thru my hands.  Refinishing the cabinet was a bonus.  The only time constraint I have put myself on is to have it back together by the latter part of September.  I'd like to see the TV work, however it's going to work, by then as well.  I can sort the TV if necessary next summer.  I'd like to put the completed ST in my den in AZ.  Getting it out there will be another engineering feat.  It will need to be at least partially crated. 

Going thru this Stereo Theater and learning of it's history has been a fascinating journey.  Would I do another to this degree?  Who knows.  I try to never say never.  While I'm not out of the woods by any means, there have been no real problems with this restoration.  Everything has been pretty much what I expected.  The incident with the picture tube was the closest I have come to a tragedy working on it.  I was scared enough to be well-prepared, so it all worked out.  I've read where nicotine is a deal killer, but it has not really presented a problem with this job.  There have been several members of this forum who have made contributions to the finished product.  I have enjoyed every second of bringing this thing back to life.  I am slowly learning about TV, something both of my "elmers" have discouraged.  I have made lifelong friendships dealing with this old neglected Stereo Theater.  A 1961 model would have been easier to restore.  The 1962 Stereo Theaters were a mishmash of kluged-together left-over components, poorly documented, and not "standard" in any regard.  It still has the traditional Magnavox hardwood cabinet, but it was finished in lacquer.  And this particular example lived a great part of its life in a home with poor housekeeping and heavy smoker(s).  Electronic works of art, these are.   

Another tidbit I've learned on this project.  There is a procedure, touted as "The Treatment",  a miracle, on "that other forum" which employs Go-Jo hand cleaner, the kind without pumice, and 0000 steel wool to clean cabinets.  I have used that method with varying results.  But, on this cabinet, it took the finish off to bare wood.  And I found Go-Jo difficult to remove from bare wood.  I soaked the small area I used it on several times with lacquer thinner and acetone before I got all the Go-Jo out of the bare wood veneer.  Not only are the mineral spirits, petroleum solvents, in the Go-Jo hard on the glue holding on the veneer, its residue prevents stain from taking.  If I had used this stuff on the entire cabinet, I could have had a mess on my hands.  I am not a fan of "The Treatment" and caution about its use.  You need to test an inconspicuous area first.  I used it on my Concert Grand using just a terry cloth rag.  That was plenty aggressive on a good finish.  I'd say if "The Treatment", using steel wool, actually improves matters, the cabinet should be refinished.  That is just me and my experience.  Your results may vary.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 26, 2019, 05:28:25 PM
I checked out the changer this afternoon and did some cleaning on it.  It had the usual scum of cigarette smoke residue like everything else.  It cleaned up real nice.  It's in pretty good shape.  The only thing I see is that the platter pad is hard as a rock.  I have a couple others like that, so I'll share the felt pad I use on them with this changer.  I may have my first Electro-Voice model 132 cartridge in this changer.  This is the first one I've seen.  The mechanical needs are a new drive tire, clean and lube the motor, then give the rest a lick and a promise.  This thing has the only nice set of motor mounts I have ever seen in an old record changer, period, let along in a Collaro.  They are soft and pliable and look like they were installed last week.  Of course, it gets a new needle. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on June 26, 2019, 09:04:54 PM
The incident with the picture tube was the closest I have come to a tragedy working on it.  I was scared enough to be well-prepared, so it all worked out.

There's some value in being scared.  I try hard to always be scared by the table saw and the circular saw.  Fright inspires respect which leads to caution.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 29, 2019, 01:03:01 PM
We got the finish sprayed this morning.  The temperature rose too high and we had to quit before we got the top completely done.  Ron's method of spraying gloss poly so it does not look so glossy is amazing.  Top secret, but amazing.  The top we are going to spray full gloss, then I'll sand it down a bit.  Why not just use semi-gloss material to start with?  Semi-gloss is too dull.  Satin poly is essentially flat.  The humidity here at 10AM was 78% and the temp was 85 degrees, so we have to wait 72 hours then respray the top and sliders.  We had a spray gun faux pas, and that delayed the start of activities by 30 minutes, probably the difference between getting done and not.  No biggie.  It took over 50 years to mess the ST up, so waiting a few days to make it right is not going to hurt anything.  This thing will look amazing when we get it done.   ;) :)

Next one in line is the Zenith 5-S-127.  It gets the same treatment. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on June 29, 2019, 01:45:01 PM
Yeah, most non-glossy finishes contain fillers to make them look flat.  That also clouds the finish up a bit.  Looking forward to your photos.  Meanwhile. since I have extra brothers around, I replaced the Chevy's seat belts today.  Fine threads, exposed to salt for many years, and sitting in place for 58 years....  We got out the long socket handles and the 1/2" drive sockets.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 29, 2019, 02:50:50 PM
We are not done yet.  As I watch the finish cure, I see we need more material.  We have applied five coats of finish, plus I applied two coats of shellac, plus stain and grain filler.  I put 15 coats of finish on the 616 I redid a couple years ago.  Magnavox advertised "10 coats of hand-rubbed finish" so we are not there yet.  I like the progress so far.  The stain is even, the condition of the cabinet is acceptable.  We have decided you need to apply more material to a Magnavox cabinet than you do to a gun stock.  Where we are right now does not feel "luxurious and milky" like a Magnavox cabinet should.  This may take four or five sessions to get enough material on.  I'm satisfied with Ron's new procedure, it will just take more of it.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: walyfd on June 29, 2019, 06:03:54 PM
Original finish was most likely lacquer over sanding sealer.  I'm using this method on the makore veneer in my 62 Fleetwood.  I've learned it has to dry, dry, dry before the polishing stage.  I used 2 coats of sealer and hit each coat with 0000 steel wool then started light coats of spray lacquer.  Let that dry a week then hand polished with maguires car products. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on June 30, 2019, 11:10:05 AM
The 1962 Stereo Theater cabinet is the second Magnavox cabinet I own with lacquer on it from the factory.  My 1963 "Contemporary" is the other.  The 1963 cabinet is still the traditional hardwood cabinet, but it has more cheesy trim and has a lacquer finish.  I will go to my grave believing that the Concert Grand, Imperial and Symphony were not originally finished in lacquer.  There have been discussions on this, some type of oil, tung, Danish, teak, whatever, but not lacquer.  The Stereo Theater cabinet had a poor finish applied at the factory.  The toner and finish were applied in one application.  You can see where the inside of the cabinet was oversprayed.  There was NO way I would use lacquer on this cabinet, considering the amount of work it is to take everything out so I could work with the cabinet.  I considered using lacquer at one point.  I've been using polyurethane since it came out.  I've had good luck with it so far.  This is the most complicated and the largest cabinet I've worked with.  There are lots of surfaces to make sure are all coated evenly.  The bottom edges of everything was bare from the factory.  We had to make the first pass with finish with the cabinet on its top.  Then on its back.  Then sitting on its wheels.  Our working conditions aren't the best for an item this large.  We are not out of the woods yet.  We are having fun and maybe learning something in the process.   :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 01, 2019, 06:47:52 PM
The humidity is too high to continue refinishing the cabinet.  We are done until maybe July 4th morning, early.  The humidity is alleged, via the local weather guesser, to be lower that morning.  What we have done so far looks good, and it is sanded waiting for the next coat. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 03, 2019, 08:32:15 PM
Testing, testing..... ::)

Ah ha!  Got it.  Here is the picture of the 417 I have been trying to post.  Notice the finish is really shiny.  This cabinet is in dark walnut.  Also notice no pulls for the front sliding doors and that it is a five-knobber.  This cabinet has some wear to the finish, but it's very nice still.  I believe Ron's top-secret procedure should get us pretty close to this level of gloss.

These are pictures of an instrument that was for sale on Craigslist in Georgia a couple years ago.  IIRC, they were asking $600 for it.  I don't know if it sold.

I notice this instrument is a Run 2 instrument.  That may account for the five-knob tuner and the TV dial that lights up under the tuning knob.  Mine lights up above the tuning knob.  This may have something to do with the remote control on mine. Interesting....... :)

We had a "two-inch shower" (two inches between drops!) this afternoon.  It lowered both the temp and the humidity.  We have another spray procedure scheduled for 6:30 in the morning.  Let's keep our fingers crossed...... ;)

The last picture is mine, for reference.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on July 03, 2019, 10:59:48 PM
Wow, I'd settle for latex house paint if it meant I didn't have to get up at 6:30 a.m.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Alfista on July 04, 2019, 12:08:42 AM
Ah ha!  Got it.  Here is the picture of the 417 I have been trying to post.

Thanks for posting those pics! That's the first one I've seen with the same 5 knob, TV tuner & wooden bezel that's in my '62 357. Oddly, the two are rotated 180 degrees. Mine is also walnut, and in Georgia. I wonder if there's a connection...
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on July 04, 2019, 07:57:50 AM
Interesting photos of the one for sale in Georgia.  Very silky looking finish.  ;) :)   I think I like your light walnut better.  It's something different, something you do not see all that often.  In the last photo, which is yours, I think I recognize the back ground.  ::) ::) ;) ;) ;) :)

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 04, 2019, 09:12:17 AM
Before I forget what I've read...... ::) :-[

Tim, I'd like to have more pictures of your 357 for my files, if you'd care to share.  That is the first ST I have seen with reversed tuners.  Good old Magnavox in 1962..... :-\ ;)

Chris, 6:30 may be the official time we spray  from now on.  No breeze, no dust, minimum overspray, cool outside to work.  We'll have the coffee started sooner, though.   ::) :)

Bill, I believe you or Bob were responsible for the picture of mine I posted.  You were in full "co-conspirator" mode when this shot was taken.   :) :)

Other than my forgetting to turn the coffee pot in the shop on so it would be ready on time (!!! ::) ::)) the morning spray session was ultra-successful.  Low temps, low humidity, no breeze, no dust.  This thing may be a Magnificent Magnavox yet, one of these days.  I started the A/C in the shop about 5 am so we could pull some of the humidity out before we started.  Water runs out of that air conditioner like it was attached to a water faucet here lately. 

The only hitch so far is the sliding lids.  I have stripped them twice and still have some kind of contamination that shellac won't fully seal.  The areas I used Go-Jo on to clean are the worst.  Officially, as of this very minute, I will not use Go-Jo on a wood surface again.  It might work okay on a good finish that is just dirty, but if it goes to bare wood, or even contacts bare wood, you can't get the stuff out of veneered tempered Masonite.  Ron is going to try a cheat he uses on gun stocks with oil contamination.  We'll see how that works.  I would highly recommend NOT using "The Treatment" on wood you may have to refinish.  The only thing I'll use the stuff for is to clean my hands or something that is metal.   >:( >:( ::) :-[ :-\ ;) :)

I have never had experience with any contamination in the past that shellac would not seal.  I like using waxed shellac for filling and smoothing, since I spray it on heavier.  I like following that with dewaxed shellac before the finish coats.  Minwax says not to use waxed shellac under polyurethane.  I did that on my 616 and it worked out fine.  On these lids, I have tried waxed, dewaxed, both and none and still have fisheye.  Only in the areas where I used Go-Jo, not the entire lid.  I used waxed shellac on the entire cabinet and have no fisheye anywhere except those lids.  If the cheat, scheduled for 10am this morning, does not work, our next step is to spray a wash coat of shellac, followed by a coat of lacquer with fisheye preventer, then sand, then a washcoat of dewaxed shellac, then more polyurethane.  That seems like a convoluted way of getting around fisheye, but I don't want to strip those lids again.  There is only so much abuse you can give those Masonite lids and not risk them coming apart.

 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 04, 2019, 10:57:36 AM
I have had two blessings when it comes to refinishing this cabinet.  First is Ron the Refinisher, who is a sheer genius when it comes to spraying anything, particularly urethanes.  Next is an air conditioner in my shop.  This allows us to control the humidity as the panels cure.  Ron could spray mayonnaise on a brick and make it look the way he wants it.  He was not the least bit concerned.  I was frantic.  The method he used was to mist a coat of dewaxed shellac, this followed immediately with a mist coat of satin poly.  He waited about five minutes, then applied another two mist coats of satin poly.  We'll let this dry for a couple days, then power sand with a quarter-sheet sander and 220 grit paper.  This will flatten the film so we can spray full gloss material.  It looks perfect now, except it has no gloss whatsoever.  I'm impressed.   :) :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Alfista on July 04, 2019, 11:15:01 AM

Tim, I'd like to have more pictures of your 357 for my files, if you'd care to share.  That is the first ST I have seen with reversed tuners.  Good old Magnavox in 1962..... :-\ ;)


Will do, Greg. 8)  Be warned, I'm slow.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 04, 2019, 11:53:17 AM
I appreciate whatever you care to share.  I'm in no hurry.  I try to get pictures of every Magnavox instrument I can find for my files.  And I thank you.   :) :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 05, 2019, 10:21:54 AM
Tim, another thing I noticed.  The 1962 Magnavox catalog shows a 1MV357 without remote control, and a 1MR397 with remote control.  There is no "MR" 357 listed with remote control, but, clearly, yours has remote control, as evidenced by the little red knob you push for motorized tuning.  So, I guess my next question is this.  Is yours a 357 or could it be a 397?  I'm not asking to contrary your statement, but, if it is a real 357 with remote control, it may be outside the "regular" production specs, if that ever existed with Magnavox.  Yours may be more rare than we realize, if it is a remote-control 357.  Sort of like my 418 starting its life as a 417 and leaving the factory with two types of grille cloth, one of which I have never seen on anything else Magnavox has built.  I have never seen another Magnavox Stereo Theater of any year built with reversed tuners.  We have examples, in this thread, of three 1962 Magnavox Stereo Theater instruments built with features outside of what is documented to be "regular" production specs. 

The more I delve into 1962 model year production from Magnavox, the more I'm convinced that there was little in the way of "regular" production specs.  It's probably fair to assume that they built some stock of regular production components ahead so they could keep assembly lines moving.  It may also be fair to assume that Magnavox worked diligently to use up tube components as they transitioned to solid state during 1963 production.  The 1963 catalog does not mention all-tube Stereo Theater for 1963.  I have never seen one.  I have always believed that the 1961 model year production was its most interesting.  I'm beginning to change that belief to the 1962 production.  Magnavox has been difficult to document up to 1962, and has become more difficult in 1962.  One needs to refer to date codes to make an educated guess about a 1962 Magnavox.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Motorola Minion on July 05, 2019, 04:09:24 PM
The knob on Tim's 357 is identical to the one I have for you. I have a selection of 3 channel-number wheels too.

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Alfista on July 05, 2019, 08:26:18 PM
Greg, it's a 4MR357P. Of course, 1962 is a best guess.

Nothing adds up right, and I assume it's because Magnavox had already begun to change over to solid state production and was using up their stock of tube parts in whatever manner they could to get them off the shelves.

It's a 5 knob unit with the 9300 amp and the 12" 8-speaker system, 24" tube. I can't recall the changer model. Originally sold right here in South Georgia to the home I removed it from. I don't recall any date codes. We're out of town for the weekend, I'll see if I have any useful pics when we get home.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 05, 2019, 10:54:33 PM
Tim's ST has the best picture of that knob I've seen.  My number wheel is okay as far as I know.  A question I have is this.  Are the inner knobs different for the ones that illuminate above the channel knob and the ones that illuminate under the channel knob?  Mine illuminates above the channel knob.  I'm guessing the knobs are the same, but the channel wheels are different.

1962 is probably dead on.  That model was not listed in 1961.  Remote control is not listed as an option on anything other than the "400" series with the 27" picture tube, either in 1961 or 1962.  You have a very unique instrument.  Any pictures you'd like to share would be most welcome.  Most of the Stereo Theaters in 1961 and 1962 has the 93 series amp.  There may be exceptions, and I'd be interested in documentation of any of those that may be out there.  Magnavox would build anything somebody was willing to pay for.  And, like you said, they were using up leftover tube components while they rolled out their new solid state lineup.  The eight-speaker system with the 93 series amp is a remnant of the Symphony series, although they used 15" woofers.  Is the remote in your 357 solid state like in my 418 or tube like in 1961?  Is your TV chassis separate from the picture tube, or does it slide out in one piece? 

This thread has had 22,307 hits.  I appreciate everyone taking time to share this adventure.   
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Motorola Minion on July 07, 2019, 08:05:25 AM
The knob on Tim's 357 is identical to the one I have for you. I have a selection of 3 channel-number wheels too.

Most of the models had top-reading wheels like Tims, not side reading. The FT inner knob and the selector knob with a keyed pair of flanges to engage the channel wheel was universal - I think.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 07, 2019, 08:41:51 AM
Thanks, Dave.  I appreciate all you have done.   :) :)

Our Sunday morning spray session got shortened due to sprinkles.  We are getting close, but we had to quit before we were done.  It's my fault.  I should have been ready to spray a couple weeks sooner. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Motorola Minion on July 08, 2019, 09:42:51 AM
The knob on Tim's 357 is identical to the one I have for you. I have a selection of 3 channel-number wheels too.

Most of the models had top-reading wheels like Tims, not side reading. The FT inner knob and the selector knob with a keyed pair of flanges to engage the channel wheel was universal - I think.

Lets not forget this 546 Theatre (yes - it was a multi-year budget model after the rectangular color theatre was introduced).
It did not sell  :( and was parted out, both UHF and VHF read on the bottom.
I almost took this home for $75 at a swap meet a year ago, but it was on its way to the "strip and burn pit" at Kutztown before I got the courage.
Greg is doing such a thorough job on the monochrome 27", there is no point converting to color now - wink! Besides that, the Astro-sonic in the 546 is a modest 20 watt 5-knobber.

Now, if that 1962 three-piece theatre (CTC11 clone) would show up somewhere, one can only dream.  :-[

Greg, Send me a PM with your address and I'll see what the postage is.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 08, 2019, 10:51:24 AM
The man I bought my ST from had a color ST he was parting.  I got the remote control setup, speakers and amp/tuner chassis out of it.  I considered putting the color TV in my ST, but the color one had a fairly bad cataract, the repair of which is absolutely above my pay grade at this point.  Plus, that was not "original" if any Magnavox was ever "original" and I felt I might have been really pushing my luck.  I'm not out of the woods with a black and white TV set yet.  I hate to see any Stereo Theater going to Kutztown's burn pile.  That doesn't seem like a fitting activity for people who allegedly restore old electronics.  A ST is a marvelous feat of engineering on one hand and a corporate kluge on the other hand.  The old radio guys get their hormones flowing (and their checkbook out) for an old AM Zenith radio with a cat sitting on it, but will throw a perfectly useful piece like a ST on a burn pile.  That makes no sense to me.  ::) :-[ :-\ ;)

PM on its way, Dave, and many thanks.   :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 08, 2019, 09:48:20 PM
I spent some time this afternoon cleaning the bracket that holds the picture tube.  It was covered in green gunge from cigarette smoke.  I had to use steel wool and sandpaper to get the dirt off.  By the time I had it cleaned, I also had it polished.  Magnavox used some really pretty, easy to polish metal.  I used a dab of Simichrome and got it looking really fancy.  Now if the picture tube makes a good picture, I'll be set.  If not, I'll have the prettiest dud 27ZP4 on the face of the planet.  This tube and bracket will set on its stained, grain filled and finished shelf.  Again, by the time I got that shelf looking halfway clean, it was really fancy-looking.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on July 08, 2019, 11:53:59 PM
I share the thoughts about burn piles and other destructive behaviors.  They aren't making any more of these old devices and we have an obligation to preserve those that happen to come our way.  Some collectors focus only on top-grade, high-end pieces.  I specialize in whatever intersects with my path, and those are rarely perfect or unblemished.  That just makes it more of a challenge.  My method isn't the route to wealth or fame but it does offer challenges and fun.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 09, 2019, 12:03:26 AM
Hi Gregg,
               It's probably already been mentioned on early pages of this 36 page tome, but in case not, the download called "Getting the Most From Vacuum Tubes"
had lots of little known tricks to restore and maximize the life of all tubes, and especially picture tubes. I had read this wonderful book a LONG time ago, but until looking at it again yesterday in the light of so many of the posts on this forum, it hadn't really sunk in. For example, Bill had recently been working on a chassis of a single-chassis Magnavox AM FM SW console, and I believe he had done some voltage readings with the chassis inverted. Later he was blowing fuses and the problem was a bad 5Y3. This book mentions that well-worn tubes like the 5Y3 had "sagging" tungsten filaments and when operated in positions other than straight up, might sag towards the plate and that is probably why Bills 5Y3 filament shorted to the plate soon after it was powered up upside down.
             Anyway, the book mentioned many ways of restoring emission of an older worn out picture tube and described certain operating conditions that weaken the tube prematurely. I think you mentioned that you have a CRT restorer, but even if you do and have already used it on other TVs, rereading the sections of this book about CRTs will let you do the best job possible. I remember reading a little known fact about CRTs and that they all have 12 volt volt filaments to make them less prone to burnout. Also one or even two "picture tube brighteners" can be used (which raise the filament voltage by 20 % or so) without danger of burning out the filament. I mention this because one of the picture tube restoration methods is to increase the filament voltage by 50 % and draw cathode current about twice that of normal amount for several minutes,. I have already forgotten the details, even though I just read it yesterday (yeah, it's that bad) so you had better look that book over before juicing up the voltage based on my lousy memory.     .
              I sure hope you have a nice bright sharp picture as a reward for your labors. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 09, 2019, 07:27:21 AM
My collection is nearly 100% "undesirables" and orphan junk.  The only things I own that people would get halfway excited about are my Coke radio, the Concert Grand and my TV-7 tube tester.  The Coke radio is not worth 10% of what it was when I bought it.  I haven't seen one sell recently.  The Concert Grand gets hormones flowing, but, in my opinion, they test the P.T.Barnum theory every time one comes up for sale.  Magnavox made better stereos than the Concert Grand.  The TV-7 is just a cheap military tube tester that people have decided are special for some reason.  Like Western Electric stuff.  I don't get that at all.  A Zenith Strat is a high dollar AM radio.  It won't do anything more than a little clock radio will.  Somebody decided it was special and the "narrative" carried that to silliness.  The snoots turn their noses up at almost everything I own.  Orphan stuff has given me hours of fun and enjoyment.  And I like "cheap".  Cheap (or free) is good. 

Any rectifier that shorts, for any reason, is a menace and needs to be eliminated from the face of the earth.  How are you going to work on something unless you tip it up so you can access the underside of the chassis?  Good to see you post again, Ed, and thanks for the encouragement.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 09, 2019, 02:34:17 PM
I gave the cabinet its final rubdown with 0000 steel wool.  The last two coats are tentatively scheduled for 6:30 Thursday morning, pending how high the humidity is.  This will be the final two coats for the cabinet.  We still have work to do with the sliders, since they are two coats behind the cabinet.  There will be 17 coats of polyurethane on the cabinet if we can get the top to flow right.  These are somewhat thinner each coat than what we put on the 616.  Ron says we "baptized" the 616 in poly.  We had to do thinner coats this time due to drying times being extended.  Instead of three hours between coats, we have been giving it three days.  This cabinet should not be as much work to work out the finish as the 616 was.  I'll work this finish next spring.  If all goes as planned, the dust nibs should float to the top by then.  It has been damp enough that dust has not really been a problem.  High humidity is good for something.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 10, 2019, 02:17:17 PM
More little details I enjoy fiddling with.

The brackets the picture tube sits in is lined with cord strips to cushion the glass from the metal brackets.  This cork material has shrunken and deteriorated.  That may be part of the reason the picture tube fell out when we tipped the cabinet onto its front.  I found that Hobby Lobby has rolls of cork, 2" X 10' that has adhesive on one side.  This material is perfect for replacing the cork strips on the picture tube bracket.  I left the original dirt so I could tell where the brackets are supposed to be positioned on the picture tube.  They really won't go back on wrong.  They won't grip the tube if you get them positioned wrong.  The only thing I see is that I may not have the tube adjusted front to back properly to fit the mask.  There may be some putzing necessary when it comes time to put everything back.  That's why we practice using swear words, right?   ::) :-[ ;) :)

I cleaned all the gunge off the mask.  The next step is a trial fitting of the mask, safety glass and all the trim.  I took pictures, but I already have an issue that I did not take a good enough picture of.   ::)

I'm not sure how tight I need to get the clamp around the picture tube that holds the mounting brackets.  How tight is too tight? 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Motorola Minion on July 10, 2019, 03:39:58 PM
The strap around the CRT has either a nut and bolt or it is like a worm-screw hose clamp. Make it snug enough to keep the brackets in position and not much more.

Tightening the band too much may cause friction as brackets seat into position. I always tightened these when the set was face down and CRT was resting on the mask (if the mask is metal or hard plastic, file off any sharp edges), the brackets are aligned but not tightened down. I would then stand the set up and see if the CRT moves out of position to be sure.

Just avoid any point stresses on the glass and you cant go wrong. Use a face shield when handling a CRT that requires external safety glass.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 10, 2019, 06:49:46 PM
That is about what I've done.  Just tight enough nothing moves.  I don't have a face mask, but I use some clunky old safety glasses.  I just avoid impacting the rear of the tube for any reason.  Thanks, Dave.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on July 10, 2019, 11:40:10 PM
I wonder if your cork is going to compress some, and need retightening, sort of like retorquing head bolts after a few hot/cold cycles.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 11, 2019, 07:40:13 AM
I'm sure it will.  If I manage to get the picture tube back in, the mask and safety glass will keep it from falling forward.  The brackets are made in such a way the tube is unlikely to fall backwards.  The original cork was dried out, dirty and broken.  The brackets were contacting the glass on the tube. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 12, 2019, 08:30:58 AM
We now have a total of 18 coats of material on the cabinet.  This is scheduled to be its final coat.  We'll see how it flows and go from there.  The front doors and the top sliders are one session behind, so we'll sand this evening and hit them again tomorrow afternoon.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 12, 2019, 11:13:06 AM
So far, about four hours after the last coats were applied, everything looks good.  We are going to wait about a week, then turn the cabinet on its top to replace the pilot light and Magnalux sensor.  Then the speaker panels with grille cloth all go in.  Then the picture tube, then the TV tuner and external speaker switch.  Then the mask and safety glass go in front of the picture tube.  We have another session to work on the sliders scheduled for Saturday afternoon sometime.  With the cabinet on its top, I have made notations in my restoration file to clean any finish off the wheels we may have inadvertently gotten on them.  If nothing shows up as the finish cures, we are done with the main cabinet.

This cabinet is not the easiest one to get an even finish on.  I have learned lots of little tricks on this project.  There are so many differently-angled surfaces that work against each other when spraying finish.  This cabinet really could use an airbrush in some areas rather than a spray gun.  We used a DeVilbiss gun.  The only real problem we had was the fisheye situation on the corner of one lid.  The one I used Go-Jo on.  Satin poly bailed us out on this one.  That stuff sands as easy as shellac.  It did not hide the grain.  There are lots of "feature" in the "furniture" that we did not want to hide.  Gun stock guys call the wood on a gun "furniture".  We can't make a determination on gloss at this point.  As poly dries, it gets shiny.  Then, as it moves, shrinks and fills, it loses some of the gloss.  I'm sure there are areas we'll ultimately need to work.  I only see one dust nib I need to do something with and it's on a slider.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 13, 2019, 04:29:56 PM
I spent a couple hours this afternoon finishing up the cleaning process on fasteners and doodads needed to put everything back into the cabinet.  Unless I have overlooked something, I believe I removed the last of the cigarette smoke residue.  All the little brackets and doodads have part numbers stamped into the metal.  I thought that was different, not something I would expect. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on July 13, 2019, 06:09:57 PM
We're all waiting to see the final product.  And maybe a video of the TV image, too.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: walyfd on July 13, 2019, 07:18:25 PM
You probably added another 12 pounds to it with all that varnish!!!

I bet it'll be beautiful.  I'm not repeating my mistakes from my first car restoration...  the '62 is going slowly but I'm not stressing.  I "see" the final product and am enjoying the process and small victories where before, I was like a tornado. 

I can appreciate your restraint in wanting it done right versus fast.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 14, 2019, 11:51:48 PM
This will be our second hot-rodded polyurethane finish on a Magnavox cabinet.  I fully expect this thing to be magnificent when it is all done.  It will not be done for at least another year.  While the finish cures, I'll have time to see what the TV and remote control are going to do. 

I used a quart and a half of shellac.  I used almost a quart of satin poly.  We sprayed on two quarts of gloss poly.  Plus grain filler, plus stain.  There is no surface on this cabinet anywhere that does not have some type of finish on it.  No bare wood anywhere.  Partly for preservation, partly to rid the wood of cigarette smell.  I used satin poly on the inside of the cabinet in spots.  The only thing we taped off was the record changer compartment.  The paint on it is good enough all I did was clean it.  The rest of the cabinet interior was oversprayed  with finish as we went along. 

A video of TV performance may be a tad above my pay grade.  I will be quite satisfied taking a still picture of a working TV. 

I have some pictures I'll share.  Life has gotten in the way of downloading them.  My camera has the nasty habit of spitting out its batteries halfway thru the download.  That causes a mess.  The latch on the battery compartment is on the fritz.  Not repairable.  New camera time.  I'm using shipping tape.  Crude, but effective.  I know how to use this camera.  I'm not looking forward to leaning how to use its replacement.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 15, 2019, 02:08:42 PM
Since I got rained out mowing, I tinkered with my camera a bit and got these pictures downloaded.  The first picture is a "before" picture.  The next picture will be a similar shot of how it looks now.  The lights in my garage are not the best for taking pictures.  They are too glary.  I could not get good shots of the features in the wood.  If you look at the second picture I posted, the top looks darker than the sides.  If you look at the picture taken from the side, the top matches.  The wood on this cabinet is amazing.  It is not quite as light in real life as it looks here.

If the top picture is not evidence enough of why not to put lacquer on a cabinet, I don't know what would be.  Look how much dirt that finish absorbed.  That would not happen with a tougher finish.

The top sliders will get another double coat of finish.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on July 15, 2019, 06:27:49 PM
It looks amazing Greg!  Not at all what I remember while I had it stored waiting for your pickup.  It really will be "Magnificent" when done.  :)

Bill

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on July 15, 2019, 06:42:15 PM
Wow!  Now I'm waiting to see how it looks "all dressed up" with grille cloth and innards.  Certain to be very impressive.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 15, 2019, 09:10:40 PM
We got this evening's session called due to rain.  One of those "two inch" rains where the drops are two inches apart.  It has spit rain here most of the day, thanks to the remnants of tropical storm Barry.  We are scheduled to resume activities tomorrow evening.  I hope that session concludes the spray portion of the finish.  It is supposed to get hot, in the middle 90's, starting Wednesday with humidity to match.  They are saying "feels like" temps near 105.  I was not going to post any pictures until I got the grille cloth and picture tube in, but I got in a hurry.   ::) ;) :)

Thank you for your interest and words of encouragement.  Ron's the man when it comes to spraying any type of finish.  I'm well satisfied up to this point.

I have just over 150 hours in this so far.  Plus 18 hours for Ron.  So, if you could find somebody to actually do what I have done and were paying them $40 per hour, you would have $6000 in this already and would not be done.  We are over half done, maybe 60% done.  We have re-assembly and sorting the TV and remote and changer left.  One could have nearly $10,000 invested in a $50 Stereo Theater if you had to pay to have it done.  I figure at least 50 hours left.  I have about $300 in parts, plus the transportation to get it here.  I still have a quad of output tubes, changer parts plus miscellaneous yet to buy, so my $500 parts budget will be pretty close.  Ten hours next spring should get the finish worked, I'd think.  :) :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 16, 2019, 09:02:12 PM
The big event for today was the installation of the "Magnavox" script on the front lower corner of the cabinet.  (Thanks, Roger!!  :) :) :))  That sets the front off and is a welcome addition to the project.  We sprayed what we hope to be the final coats of finish on the top sliders about 7 this evening.  The heat index is supposed to be in the 105 to 109 degree range here thru Sunday, so any finish work is impossible until the first of next week. 

The next step is scheduled for Saturday morning.  We are going to flop the cabinet onto its top, then install the Magnalux sensor and the pilot light along with all the little doodads associated therewith.  And clean the wheels.  Then the picture tube goes in, then the TV tuner, then the mask, then the safety glass and all its trim. 

The grille cloth will be here in 5 to 10 days.  I procrastinated, not being able to choose which I wanted.  I can install the picture tube and that and not be getting ahead of myself.  The grille cloth technically should go in first.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on July 17, 2019, 06:00:32 AM
Progress!  And, the weather cooperated so you do spray last night.   :) :)  Of course, we all want to see photos as you get things put back in place.   ;) ;) :) :) ::)   The weather guessers say we are to expect temps in the 90's with humidity to match now through the weekend.  It's summer, so I'm not really complaining.

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 17, 2019, 10:44:45 AM
The sliding lids look good at this point.  We'll see what Ron has to say, but I'd say they are done.  It's time to move on.  We may do more harm than good trying for perfection, given the weather conditions and considering my outside "spray booth."  I reckon if somebody sees it and doesn't like it, I'll ask to see theirs so I can lay my eyes on perfection.   ::) :) ;)

I got flamed pretty good on ARF one time when I told a guy this very thing.  Not much of a sense of humor for some of those guys over there.   ::)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on July 17, 2019, 09:25:34 PM
Life isn't much fun without a sense of humor to cushion the disappointments, minor setbacks, and annoyances.  The humorless folks aren't much fun to be around.  Somebody on ARF was offended that I put the wrong speakers in the little console.  I was going to upset the carefully-engineered tonal balance, basically.  And my new speakers were for sealed enclosures so they'd be awful in open-back.  It would be a disaster.  But what I knew was that the wrong speakers were better AND cheaper, and if they didn't work, surely there would be another place for them.  And so far, they sound pretty damned good to me.  I've never quite caught on to condescension so I just reply in good faith.  It's not worth picking fights.  Don't let their problems get turned into yours.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 17, 2019, 09:49:50 PM
I believe it sounds just fine with those speakers. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on July 18, 2019, 06:22:54 AM
Right or wrong speakers, it's how it sounds that counts.  And, if you are happy Chris, that's all that counts.   ;) :) 

Bill

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: firedome on July 18, 2019, 09:07:55 AM
Nice work! This, though perhaps not perfect, and what is, will still be the world's nicest restored Maganvox Stereo Theater when finished!
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 19, 2019, 12:08:44 PM
I re-installed the trim pieces that attach to the top panel on the cabinet.  Big deal, you say, that's a 30 second job.  True enough, but, we put a thicker finish on than the factory had.  So the trim pieces that fit on the edge of the panel would no longer fit.  One needs to be careful, lest you booger the ends of the panel and knock off the finish.  I found a pair of snap ring pliers that worked perfectly to slightly spread the tabs on the trim.  I started the trim on with the rolled top first, then, using the wooden handle of a tack hammer to tap the bottom of the trim onto the cabinet.  No harm, no foul.  They are sufficiently tight and I believe they'll be just fine.  If they prove too loose as the finish cures, I can squeeze them a bit.

The one slider with the fisheye problem is not satisfactory.  As it cured, I find we still have a slight imperfection in the area where I used hand cleaner.  Another couple coats of satin poly after a good sanding is the next step for that.  Fortunately, this lid is separate from the cabinet and won't hold up progress any.  Going forward, I am going to keep home remedy chemicals away from wood finishes until I determine the condition of the finish.  And forever away from the finish on a sliding lid made of veneered tempered Masonite.  I can't be aggressive enough with acetone to float the contamination to the top. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: 19and41 on July 19, 2019, 07:28:23 PM
The cabinet looks mighty nice!
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 19, 2019, 10:54:14 PM
Thank you, Rex!  I appreciate those kind words.   :) :)

The grille cloth arrived today.  It was supposed to take 5-10 days from Ohio.  I got the cheapest shipping, which was still $6.95.  I got the cloth at Parts Express.  I haven't opened the package yet.  I also ordered caps for the crossover networks from the same place.  I got the order three days after I placed it.   :) :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 20, 2019, 06:01:09 PM
I made a little progress today.  I got up this morning in a grouchy mood, for some reason.  I got out to the shop about noon and got started.  I really like the grille cloth I got.  Time will tell how successful I was at installing it, but I'll have to say it is good to work with.  I'm glad I did not get the thinner, cheaper stuff.  I did not glue any of this cloth.  So if it stretches or whatever, I can do it again.  I put the plastic rails the front sliders run on.  I put all the hardware on the front sliders.  I put in the Channel 1 speakers and the amp.  Next session is the picture tube and the tuners.  I did not want to press my luck doing that this afternoon.

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on July 20, 2019, 06:34:11 PM
That black grille cloth looks really cool!
As to grumpy, I had the take the carb off the Chevy today.  I hate fixing things twice.   More on that elsewhere.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 20, 2019, 06:40:50 PM
How about some "before and after"  pictures?

I hope the grille cloth works out well.  I really like it.  I'm thrilled with progress up to this point.  There are six little round felt bumpers I have yet to install.  I have some, but they are dried out and won't stick. 

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: 19and41 on July 20, 2019, 09:31:01 PM
Looking good!
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on July 20, 2019, 09:32:41 PM
I vote for the new look!

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on July 21, 2019, 07:29:39 AM
Looks awesome Greg!  :) :)

Bill

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 21, 2019, 11:06:55 AM
The LH front sliding door does not slide very well.  It did not slide well before I took it all apart.  It drags on the wood.  I believe a combination of a well-placed thin felt pad and some lube on the lower track will remedy the situation.  I'll polish the wood it slides on, which may help some as well.  I thought, at first, the plastic guides the door rides on may be worn, but I swapped them side to side with no improvement.  The groove in the wood where the lower track is may be milled too deeply at the factory.  The finish was worn off the wood, so this is not a new problem.  The doors line up fairly well, so nothing appears to be tweaked.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on July 21, 2019, 11:27:56 AM
I have a sailboat with mahogany drop-boards to close off the companionway.  They've sometimes been a bit sticky in their channel, especially the one with a little warp, so I bought some ultra-high molecular weight (UHMW) plastic tape from (pause for brain fart--can't remember company name) one of the online industrial suppliers.  Makes it very slippery, and it's thin.  I has to cut it down in width to fit the slots on the boat but it has been durable.  It's clear and doesn't show.  Can't recall the plastic type-polyethylene, I think.  UHMW-PE.  You'll know the industrial suppliers; my brain just doesn't respond quickly to names.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 22, 2019, 02:00:51 PM
Life got in the way of working on this project as much as I'd planned today.  "Honey-do" type stuff.  Progress is being made, just not as rapidly as I'd hoped.

I learned something today that I should have already known.  The knobs on the radio tuner are position-specific.  I had the tuner out before and didn't recall that fact.  There was an aluminum foil-type shield under the tuner that looked rather tatty, so I made a new one out of aluminum foil.  I need to replace the crossover caps next so I can work with the speaker wiring.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 22, 2019, 02:41:27 PM
I just had something happen that is too good not to share.  Things like this happening is what makes restoration so rewarding and fun.

When I went to Bill's place to get the ST, along with the deal came almost all the electronics except the TV and changer from an Astro-Sonic color Stereo Theater.  Amp, speakers, horns, remote control chassis, two remote controls, the tuner bezel and a big bag of knobs.  There was a member who posted on the forum yesterday that he was in need of knobs for his Astro-Sonic console.  I went upstairs this afternoon looking for something else, when I came across the box I had put the remotes and the knobs in on a shelf in the shop.  I was digging thru the bag of knobs when I came upon two TV tuner selector knobs.  One was broken, one was in good condition.  I discovered what was missing on the TV tuner knob for my ST.  I am not missing an inner knob.  I am missing a clip that fits into the outer chrome knob.  I found two such clips, in good condition, and quite usable.  There is a piece of trim that was missing on my knob, available and usable on the broken knob.  So, now I believe I have all I need to get my tuner sorted as far as knobs and trim goes.  I had never gone thru the bag of knobs, since they were for the Astro-Sonic.  Dave had mentioned that the knobs for Magnavox TV sets were the same for several years.  When I saw those TV knobs, the light went on.   ::) ;) :) :) :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: 19and41 on July 22, 2019, 03:39:00 PM
I hear french or tailor's chalk is a good lubricant for balky sliders or drawers.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 22, 2019, 09:29:43 PM
Wonder would ACE hardware handle those items?  Sounds like it might be worth a try.  I really don't want oil or silicone due to wood contamination.  Graphite makes such a mess..... ::) :-[
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: 19and41 on July 22, 2019, 10:17:28 PM
I can't find it at a regular hardware.  Joann craft and fabric has tailors chalk, roughly the same thing.


https://www.joann.com/search?q=Tailors%20Chalk
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: walyfd on July 23, 2019, 04:17:19 AM
Try paraffin wax on the edges.  Available everywhere and it's basically clear. 

Check the canning section in the grocery store.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: firedome on July 23, 2019, 07:47:21 AM
The old timers used beeswax for drawer slides, works like a charm. My Grandpa was a cabinet maker and pattern maker in the '20s to the '70s, in the countryside outside of Boston, he used to keep it right on top of his workbench. I used to love to visit his shop!
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 23, 2019, 09:41:24 AM
             My mother, who probably always read those "Hints from Heloise" columns in Good Housekeeping magazine, and always had cutouts of articles with decorating hints saved for me when I stopped in, was big into rubbing old candles onto wooden drawer slides. Are candles made of paraffin ?   Everyone has old candles lying around.
              I think my mother actually looked forward to power outages at night, at least for the first half hour anyway, because within ten minutes of losing power she would have about twenty lit candles all over the place like a Christmas candlelight ceremony. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: walyfd on July 23, 2019, 10:55:12 AM
And peanut butter works on small wood scratches, too...  I remember my aunt making a paste from cigarette ashes (and she and my uncle made plenty of those) to rub on water stains.  Very low abrasion...
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 23, 2019, 02:34:36 PM
You guys have given me lots of good suggestions, much appreciated.  It had been some time since I thought about "Hints from Heloise."   :) :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 23, 2019, 04:31:33 PM
               Heloise could have been a modern day home economics version of MacGyver, the total opposite of Parris Hilton and Kim Kardashian.
               I'm sure that at least once a week her column contained new ways to hide furniture scratches, free sticky drawers and remove little white rings from glasses of iced tea left on polished wood corffee tables.  Plus removing drink stains from white cloth napkins and tablecloths, and on and on
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 23, 2019, 06:56:29 PM
Today I learned why the old TV repair guys were glad to see all-in-ones, three-in-ones, aircraft carriers, and probably some other terms we can't say in polite company go to the dump.  The TV tuner in this Stereo Theater is a horror show to put back into the cabinet.  I have it on a nice bench, made specifically for working on THIS Stereo Theater.  I can only imagine having to work on the tuner in somebody's living room, five floors up in an apartment house.  To get the TV tuner out of a remote control-equipped Stereo Theater, one would have to remove the safety glass and trim, plus the picture tube mask so you can get the bolts out of the remote channel indicator.  Then that assembly needs to be threaded thru all the wiring running every direction you can imagine.  I just pray the tuner is okay.

I have made progress on straightening up the messy wiring, but, let's face it, this is a Magnavox.  There is only so much I can do and still get it to work.  I have three more wires to extend and I need orange, green and brown wire, so I need to order some.  I have extended the phono input and the input into the amp.

AND.....I can't seem to find the thread where the member was wanting a set of Astro-Sonic knobs.  I'll post pictures here, hopefully, he'll find them.  Maybe I'll find his thread on the forum.... ;) :) 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 23, 2019, 07:02:41 PM
Yeah, the tuner bezel is cracked, was cracked when I got it, and will remain cracked since finding another would be nigh impossible.  That will be part of its personality.  I have posted a couple pictures of the TV tuner selector knob and the mystery clip.  I found half of one of these clips laying in the bottom of the cabinet when I first got the ST.  I tossed it, not knowing what it was.  I have it all together now and it appears to be just fine.  The fine tuning knob is not supposed to be in constant mesh with it's gears, so the fine tuning will not be changed when the channel knob is rotated.  This TV has an automatic fine tuning circuit that makes adjustments unnecessary, allegedly.

You can see the broken knob on the left and my original knob on the right.  The trim ring and the metal clip are now in my knob, which is in its rightful place on the tuner.  It appears to be just fine.  The upper dial indicator agrees with the lower indicator.   

I have the stereo working.  I still need to change the caps on the crossover networks.  Something I did when I re-connected everything fixed the muddy horns.  And I found a bug in the MPX I had not seen before and that improved FM stereo fidelity considerably.  I set the balance on the MPX with two VTVM's connected to the speakers.  I set the bias on the amp.  I believe I'm ready to mess with the TV and changer next.  This thing may actually outperform the Symphony, 12" woofers and all.  This thing is a sweetheart as far as stereo performance is concerned.   :) :) :) :)

I'm glad now that I did not replace the 12" woofers with the 15's that I got with the Stereo Theater.  I might have made a mess, without seeing any improvement in performance.  The Magnavox engineers knew what they were doing, even if they did mess up on the grille cloth.   ;) ;) :) :)

The bug in the MPX was........are you ready?..........are you sitting down?.........a bad tube socket connection on the 6EU7.   ::) :-[ ;)

And......just for grins, the bottom picture is the wiring when I got the Stereo Theater.  I've made a LITTLE progress........ ::) ;) :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on July 24, 2019, 07:04:26 AM
Wow, you really did make a lot of progress the last couple of days.  I'm glad to hear you solved some of your audio problems.

Bill

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on July 24, 2019, 07:58:41 AM
Love the pictures Greg. I can't even see the tuner. It must really be layers deep in there somewhere. Your patience is  admirable  !!  More than mine, at least.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 24, 2019, 09:11:02 AM
The tuner is not in those pictures.  Whoever invented that tuner graduated magnum cum laude from the Rube Goldberg Technical Institute.  All the ball bearings, detent balls, drive cable, the little plastic channel wheel are marvels of the days before computers and electronic controls.  There is a little black heavy paper thingy with a square hole in it for the numbers to show thru, that lines up with the window in the picture tube mask.  There is a little motor that turns the tuner.  There is a little switch with a red button that you can use the electronically turn the tuner from the top.  Like most of the other components in this Stereo Theater, you wonder how somebody actually threw this stuff together with any hope of it working.  Gloriously Complicated....... :) :)

Edit....I misspoke.  The tuner is in the picture of the wiring I took sideways and I got blurry for some reason.  Open that picture and hit the little icon where you can turn it up on its end....The TV tuner is to the left of the radio tuner.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on July 24, 2019, 09:20:07 AM
Try paraffin wax on the edges.  Available everywhere and it's basically clear. 


I'll second the motion on paraffin wax.  I keep it everywhere--in the shop, in the kitchen junk drawer, on the boats.   It's the best lube for bike chains:  clean the chain with gasoline, then dump it in melted paraffin wax.  I just went through that exercise on the summer commuter bike.  I can't use it on the winter bike chain because it doesn't protect against rust.  For everything else, it's a wonderful clean lube that doesn't attract dirt.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 24, 2019, 09:04:43 PM
I found part of the reason for the sticky door is a tweaked track.  I untweaked it and that helped a lot.  My wife had an old candle she could spare, so I melted some of the wax and put that on the plastic slides on the doors.  That helped a lot more.  I believe I have that little situation headed the right direction.  I thank you all for your suggestions.   :) :)

The picture tube is sitting in the cabinet.  Ron and I stuck it in this evening after supper.  It was laying on its face on the parts table.  We moved it, still on its face, to the ST bench.  We tipped it upright, then set it in the cabinet.  We connected the top braces, then put one bolt of the three in each bottom bracket.  We fitted the mask to see how the orientation of the tube was to the mask.  We moved one side just a little bit and everything was fitting just fine.  We put the remainder of the bolts in and tightened everything up.  My next session is to finish the trim on the picture tube.  I have made a list of several little tasks I need to accomplish yet, little stuff. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 25, 2019, 11:36:50 AM
The bolts are in the remote channel selector assembly.  The mask, safety glass and trim are in.  There may be a slight tweak in the mask in one corner.  I'm not sure how much of that area of the CRT will light, so I'll leave further troubleshooting until I power up the TV set.  Nothing appears to be in a bind.  It all went together quite easily with no problems whatsoever.  I put a notation in my notes on dis-assembly that there was an issue in this area and there still is.  This may be another abnormality of its personality...... ::) :)

I have the front sliding doors where they fit the cabinet and are sliding smoothly.  I may be pickier than I should be.  This is consumer electronics, not a Senior Packard headed for Pebble Beach........ ::)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 27, 2019, 01:59:00 PM
I got the picture tube sitting better than it was.  Letting the picture tube fall out of the clamp and bracket was not a good thing as far as getting it back in is concerned.  I loosened the clamp and slid the tube a bit on the brackets.  Then I found some more adjustment in the mounting holes in the cabinet. 

I put the little felt bumpers on the doors so they won't bang together or into the ends of the cabinet.  The TV chassis is back in the cabinet and everything is connected.  I still have some work to do on the "mess".  It seems the little details never end.  I get one thing done and find another that needs attention.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on July 27, 2019, 07:53:13 PM
Every little detail is one less thing to do. Remember in the beginning of this project you felt overwhelmed?  Now, after many baby steps, look how far you have come.   :) :)

Bill

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on July 27, 2019, 08:23:16 PM
As with most intimidating projects, the crucial thing is just putting one foot in front of the other to move ahead.  Then repeat.  And repeat.  Greg, of course, has illustrated this concept.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 27, 2019, 08:41:39 PM
"A journey of a thousand miles begins with a single step".  We are certainly getting closer.  About the time I think I have the wiring mess straightened up, I see something I want to do over, do differently, do "better".  I need a piece of test equipment, then I'll be ready to power up the TV.   :) :)

Gloriously Complicated!   ;) ;) :) :)

I have decided to forge ahead with designing the hotrod back for the cabinet, wild wiring be damned!  It'll still look nice.  I may get to work on that project some this coming week.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 27, 2019, 09:03:21 PM
I downloaded pictures I took during the process today.  Some of the wiring in these pictures has since been sorted, more yet to do.  I know you guys like pictures.   ;) :)

I stripped, stained, finished and sanded the shelf the TV chassis sits on.  It looks better in person than it does in this picture.  The little bumpers are in the documented factory location.  I used tan instead of dark brown bumpers.  Those front sliding doors are quite the engineering feat.  Lots more complicated than they look.  The power transformer on the TV chassis looks a little ratty in the picture.  It really looks good in real life.  I'm in the market for a new camera.  This one is showing its age.

I also see, in reviewing these picutes that I have forgotten to connect the "screen door spring" from the picture tube bracket to the TV chassis that grounds the 'dag coating on the picture tube.  Some kind of a capacitor, if I understand its purpose correctly. 

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on July 27, 2019, 11:06:11 PM
The best part of a project like this is standing back to admire it.  I have learned how to ignore the defects that I can see but others can't (lots of practice at ignoring defects!).

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 28, 2019, 08:28:39 AM
The last 5% makes the restoration.  It can also kill a restoration.  If that transformer was really ratty, that would be a deal killer.  The light in my shop is horrible for photography.  The little details that you guys are probably getting sick of hearing about is the best part to me.  Details and trivia.   ::) ;) :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on July 28, 2019, 08:43:55 AM
It's beautiful Greg!   I cannot believe it's the same unit I picked up, and stored, until you were able to retrieve it.  "Gloriously complicated", but truly "Magnificent."   ;) :)

Bill

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 28, 2019, 10:05:38 AM
It has come a long way, huh?   :) :)

I can almost say that I have had every nut, bolt and screw, component, wire, piece and part in my hands, checked, replaced, petted and polished.  I've taken it apart as far as I could take it and put it all back together.  I have reached out to the man we bought it from, but have not heard back.  I hope he's keeping up with progress on this thing.  I promised him it would have a good home and that I was going to restore it.  I'm trying hard to keep my word. 

One of these days, we can watch Perry Mason on METV on antenna with this thing.   ;) :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 28, 2019, 11:59:29 AM
Remember to pay attention to how the trim around the safety glass comes off/goes back on.  Don't ask me how I know this.......
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 29, 2019, 08:45:08 PM
I have the wiring as neat as its going to get.  The wife just gave her approval of the grille cloth and of the audio performance, so we are golden there.  She is plotting what size doilies and which whorehouse lamp belongs on the Stereo Theater.  This activity is a good sign.  This means she's going to let me bring it into the house someday.   ::) :-[ :-\ ;) :)

I have done all with the wiring I'm going to do.  If Magnavox wanted it neat, they would have built it that way.  It is infinitely neater than it was, and I've done it over so many times I'm getting sick of fooling with it.  I have reached the point of diminishing return. 

Next procedure is to make the cardboard pattern for the hotrod back for the cabinet.  For those of you who may not be familiar with what I'm talking about..... ;)

Magnavox has the nasty habit of building gorgeous hardwood cabinets with poor ventilation.  The record changer compartment typically gets warm enough to bake bread, since many times the changer is mounted directly above the amplifier.  I am planning to build a better-ventilated back out of 1/4" lauan, the thin plywood commonly used as door skins.  This material is "good" on one side and can be finished like the cabinet.  After I get it cut out, I'll sand, seal, stain, grain fill, seal again, then finish it with the same material I put on the cabinet, gloss polyurethane.  I'll work the finish until it looks much like the photofinish back Magnavox installed on Concert Grands.  I open up the back with black metal mesh so not only will the electronics have greater air flow, but the electronics will be more visible, all the "little lamps and lighties".  I made one of these backs for my Concert Grand and I may make one for the Imperial.  It is incredible how much cooler the components run when they get some air.  I make a pattern out of cardboard so any changes can be made without ruining an expensive piece of lauan.  Then I simply transfer the pattern to the lauan, cut it out, the process the material from there.

Did I forget about the TV, you ask?  Nope.  I need to buy a Kill-A-Watt device so I can measure how much juice it's drawing when I power up.  Since I'm cheap, I'm searching for the best deal.  Hopefully, within the next couple weeks, we'll have that situation sorted.   ::)

A dim bulb may not work very well on a TV chassis.  And, according to the experts on the internet, powering up a TV slowly may not be the best method, since some say if the horizontal oscillator does not start, one could redplate the HOT or could damage the flyback transformer.  The consensus seems to be that applying full power with some method to monitor current draw is the preferred way to do it.  That seems to make the most sense and the device I have seen that I find handy is the Kill-A-Watt.  This device may wean me off a dim bulb except when I'm working with small radios.  The wattage draw listed on the model number sticker on my ST is 655 watts.  The stereo should be around 320 watts or so, so that leave approximately 235 watts for the TV chassis.  I'll check Sams to see if it give anything different than that.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on July 30, 2019, 06:34:41 PM
Sams gives 165 watts as the draw for the TV chassis.  That would leave 490 watts for the stereo and the remote control.  That sounds like a lot to me, but it is what it is, I reckon.

I have the pattern cut for the new back.  I have some trimming yet to do, but it's mostly done. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on July 30, 2019, 09:11:04 PM
Check the Sams for the amp and the tuner and see of they agree.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 01, 2019, 10:27:21 AM
I have no information whatsoever on the radio tuner and no wattage given on the amp.  I reckon the Kill-A-Watt is my best bet for determining total wattage after restoration.

I have some more pictures.  This shows the original back, and also the pattern for the new one.  And it shows the Magnavox emblem that was missing on the TV tuner bezel.  I have since cleaned the dirt out of the little plastic window for the channel selector.  I overlooked it until I saw the pictures..... ::)

I robbed the Magnavox emblem from a parts set table radio I have.  I got the radio in a box of junk at an auction.  The big hole in the middle of the pattern will be filled with black wire mesh.  I am going to repair and use the original cup that goes over the end of the picture tube.  It is broken into several pieces and was held together with duct tape.  We can repair it with epoxy, paint it, and use it on the new back.  You can see how poorly ventilated the original back was.

As a side note, I'm fortunate that the chrome on the TV tuner selector knob is as nice as it is.  Many of the ones I've seen, and both the "parts" knobs I have the chrome is worn off.  I'm also fortunate to have access to this forum and its members.  Without this forum, the restoration of this Stereo Theater would not have been possible.  While I'm not out of the woods by any means, I can now see just a hint of daylight...... ;) :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Motorola Minion on August 01, 2019, 02:08:51 PM
The channel knob looks OK, is it just the metal ring/tab part that is missing? Do I see the FT inner knob there?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on August 01, 2019, 09:43:46 PM
You're right about the ventilation issue.  Heat really kills the components.  Give 'em air. 

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 01, 2019, 10:43:26 PM
Dave, I believe I have all I need as far as the channel selector knob is concerned.  The FT knob is there, it is just not easily seen.  As best I can figure, you need to push down on the fine tuning knob to set the fine tuning.  Once you have it set, it stays there automatically from channel to channel.  Since we will be watching any channel we want as long as it's channel 3, I won't need to use the FT knob much if the thing works like it's supposed to.  The remote control will essentially be worthless, if it even works, for anything other than adjusting volume and turning the TV on and off. 

Chris, for all the features of Magnavox that are Magnificent, two features are not.  Sloppy wiring and poor cabinet ventilation.  I have made extra effort to cure both issues in the Concert Grand and now the Stereo Theater. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 04, 2019, 11:38:07 PM
I'm taking a couple weeks hiatus away from the Stereo Theater.  We worked so hard on the cabinet, then re-assembly, I need a break for a bit.  I'd do this when I was restoring cars, too, after major assemblies came together.  I tend to get burnt out and lose focus.  A couple weeks "sun testing" gets me back on track.  I've been listening to it as I work in the shop, "testing" if you will...... ::) ;) :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on August 05, 2019, 08:19:02 AM
Keep testing Greg, and have fun with all the other projects that a wait you.  ::) ;) :)

Bill

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 05, 2019, 09:37:02 AM
It's been fun testing the Stereo Theater.  I may connect one of the CD jukeboxes to it.  Get a little Hank Thompson going.  I need to get the ST and the Symphony side-by-side.  If I had the Symphony dialed in like I have the ST, maybe it would not be a race.  Right now, I really don't know which one I'd put my money on....... :) :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on August 05, 2019, 04:07:39 PM
If things go right, they will be side by side one of these days.  ;) ;)

Bill

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 05, 2019, 11:41:47 PM
Yeah, someday, Bill.  We'll play the Concert Grand demonstration record to see which one sounds best.  Whadda 'ya think?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on August 06, 2019, 07:47:19 PM
I'll reserve that answer for when the day comes.  ;) :)  I'm guessing sooner than later.  ;D ;D

Bill

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on August 10, 2019, 08:33:01 PM
The finish on the cabinet is moving and filling in grain and imperfections we had when we finished spraying.  It is amazing to see this happen.  Subsequent coats of finish would partially dissolve earlier coats.  This allow the finish to move and fill slight imperfections as it cures.  I had one or two open grains on the top that have since filled.  Ron thinks it need to cure more before we try to work the finish.  It's hard for me to be patient.....

I'm going to amortize the restoration by playing some of my Faron Young records on the Stereo Theater changer.  I can't imagine them not sounding "Magnificent."
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 09, 2019, 08:45:27 AM
The Faron Young record demonstration went swimmingly well.  We have new neighbors who like playing head-banging music too loud.  They guy was amazed at how good "an old TV set" sounds.   ;) :)

I have finally acquired a method of monitoring input current on the Stereo Theater.  A "Kill-A-Watt".  A famous YouTuber who does videos on TV repair has one.  A dim bulb is not much good for something that draws as much power as a Stereo Theater does.  I've heard it is not good to bring a TV chassis up on voltage gradually, since the horizontal oscillator may not start.  This places unobtanium parts in jeopardy.  The recommended method is to start the TV chassis up at full line voltage, while monitoring current or wattage draw.  So that is our next step, scheduled for Tuesday next.  If we don't let out the magic smoke, that will be one victory.  Then if my chassis work, the "picture bulb" and the tuner are okay, we are probably golden. 

To refresh memory, the picture tube tests marginal at 6.3 volts, but wakes up nicely at 7 or 8 volts.  Who knows how long since it has been under power.  I gave the tuner and lick and a promise, so who knows what it will do.  I dreamed the other night that I started up the TV and it wouldn't work.  I found (in my dream) that the dial light was out of the TV tuner.  I guess I'll check that before I go any farther.   ::) :)

The device I have is not a genuine Kill-A-Watt, but a generic version.  I believe it is going to be very handy.  My plan is to incorporate it into my isolation transformer/variac and use it in addition, or in lieu of, a dim bulb.  The iso/variac/dim bulb I use is built into an old oscilloscope cabinet.  It has input and output voltage and amp meters.  On the device I have, you can go from watts to amps to input volts at the push of a button.  No programming, no fiddling with controls.  Simple to use.  I'm looking forward to seeing what it will do.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 09, 2019, 11:17:57 AM
I've been tinkering with the generic Kill-A-Watt this morning.  My little 1ST616 Magnavox stereo that I restored in 2017 measures 107 watts from the line.  This is for the amp, MPX adapter and the tuner.  I did not turn the phono motor on.  The Stereo Theater measures 155 watts for the amp, tuner and MPX, and I did not turn the phono motor on it, either.  Those run around 30 watts.  So that would make around 140 watts for the 616 and around 185 watts for the Stereo Theater.  The wattage given for the C36 TV chassis in the Stereo Theater is 160 watts.  That would make around 350 watts, give or take, for the wattage draw on the Stereo Theater.  The model number sticker gives 655 watts draw for the Stereo Theater.  If it draws that much, I'm liable to let the magic smoke out.  The wattage given on the model number sticker on the 1ST616 is 240 watts.  I have no idea how Magnavox figured wattage draw for their instruments.  The line voltage here this morning is 122.  That's really high for our neck of the woods.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on September 09, 2019, 06:48:51 PM
That does not make sense.  Where in the world did Magnavox come up with their watt number.  I looks like they took the actual, which is the number you have with your new Kill-A-Watt, and doubled it.   :-\ ??? ::) :o :)

So, you your post made me curious on my line voltage.  I'm at 122.3 volts as I'm typing the post.  I guess the America power grid is running high these days.  :) :)

Bill

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on September 09, 2019, 08:13:52 PM
               That sure does sound high. I think the RCA color TV chassis we had in 1960 wattage was in the 500s, and you could feel how warm the metal cabinet top got after a few hours of operation. It did not have the UHF or remote options.
           Maybe they included every option, like MPX, remote, and UHF ? That would get it a little closer. Was their a tape recorder option for this model ?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 09, 2019, 11:23:35 PM
No tape recorder option.  The remote control is not figured in my calculations, but it is solid state.  How can it draw the nearly 300 watts difference between my measurements and what the model number sticker says?  The 165 watts for the TV is what Sams gives in its drawing.  Sams has been known to make mistakes.  That spec is also for a 24" picture tube.  So, let's give it the benefit of the doubt and say 200 watts for the TV chassis before I pull the plug.  That makes a total of 485 watts to the end of the world for the Stereo Theater.  From what I have been able to learn, most all-tube color TV's of the middle 1960's range (roundies) run like 500 watts fully warm.  The wattage on the Stereo Theater slowly climbs as the components start getting warm.  155 watts was as high as it got, and that after running about 30 minutes. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 10, 2019, 10:34:52 AM
The test drive of the TV chassis did not go well....... :-[

I turned on the stereo and it ran for maybe ten minutes.  I looked everything over again for the umpteenth time and decided to turn the TV on and see what happens.  What happened was the fuse in the amp blew.  I took the amp out and put a 3 amp fuse in it, which was all I had.  The lights came on, then that fuse blew.  I have an issue somewhere.  I'm not sure it has anything to do with the TV yet.  I'll keep you posted.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 10, 2019, 02:36:54 PM
This is not looking very good.  I pulled the rectifier.  I put another 3 amp fuse in.  The dial lights came on, then the fuse went again.  Resistance testing reveals no shorts in B+.  I'm beginning to wonder if I have lost the power transformer on the amplifier chassis.  You may recall the one there now is a replacement.  It is not as physically large as the original.  The thing ran hot enough to fry eggs on after running about three hours.  With the rectifier pulled, we'll have to look in the 6 volt circuit, since that is the only one with a load with the rectifier out.  That included all the tube filaments and the dial lights.  Whatever happened was a catastrophic failure.  I have put maybe 100 hours on this instrument since I went thru it.  I don't remember having a power transformer go out in use before.  At least I know the fuse does what it is supposed to do, and it may have saved other problems, even if the PT is toast.  I have not been a fan of this PT, but figured if it worked, it would be good enough.  I don't smell anything nor do I see anything that has been leaking, nor anything that looks like it has been hot.  Better this happened at this stage then after it was done.  I'll check the schematic and see what the ratings are on the PT.  This isn't the end of the world, just one of those things that makes this hobby exciting. Now I'm beginning to wonder what happened to the original PT.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 10, 2019, 05:33:41 PM
Let's remember the theme for this restoration: "Gloriously Complicated".   :) :)

Let's remember another famous saying: "Even a blind squirrel finds an acorn occasionally".   ;) ;) :)

I expected this stereo to have a bad power transformer.  It was dead as a hammer.  It went out suddenly when it was in operation.  However, there was no overheated transformer, there was no noise, there was no magic smoke released, no tar running out, no burned wires.  It would pop fuses as fast as you could put them in.  I had to know for sure.

I ran resistance measurements on the PT and found noting amiss.  Since removing the rectifier did not clear the short, I decided to see what I could find in the low voltage taps on the power transformer.  The 5 volt tap was easy.  That was the rectifier.  The next one, the 6-volt tap, was not so simple.  I decided to pull all 19 tubes in the amp, MPX, and tuner, along with all the dial and pilot light bulbs.  This done, I put in a 2-amp fuse and applied power.  The PT with no load, by the way, pulls a little over 9 watts.  The fuse held.  No noise from the PT, no smoke, nothing amiss.  Then I started putting the tubes back in, one at a time, with power applied to the chassis, but no rectifier.  Tubes in the amp, MPX and tuner draw 65 watts.  With all the tubes back in, the fuse still held.  I put the rectifier back in and had instant music.  Like solid state.  What was the problem?  One of the three bulbs in the tuner has a dead short.  My guess is it's the one in the tuning meter, but that is just a guess.  I put all new bulbs in when I had the tuner out.  Thank God I had a fuse in the primary of the PT, or I could have taken out the PT for certain over a shorted 20 cent bulb.   ::) :-[ :-\ >:( ;) :)

I still don't know if the TV works.  After all this, I may wait for another day.   ::) ;) :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on September 10, 2019, 06:20:05 PM
That's a valuable lesson for all of us, and thank you for sharing it.  I have not been adding fuses in the primary in my restorations, mostly because it requires mental effort and I can be lazy sometimes after work.

Maybe somebody can give us a short tutorial  on sizing fuses for the power transformer? 

There's the whole issue of inrush current as filaments are cold and the filter caps charge up, and maybe a new issue of higher current draw at higher modern line voltages.  Is it enough to just take wattage from the label or schematic and add 50%?

One last point--most light bulbs fail either when brand new or when very old.  It's a bell-shaped curve with few failures once you get past "youth."  Maybe it's otherwise in those AA5 sets where the dial light looks like it's going to self-destruct at turn-on.

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 10, 2019, 06:41:50 PM
The way I determine how big a fuse to use is not very scientific.  I find out how many watts it draws, then divide watts by input voltage to get amperage.  So, if I have 120 volts line voltage and I have 180 watts draw on the device, I figure a 2-amp slo-blow fuse would be about right.  The Stereo Theater runs 155 watts and line voltage today was 121.  2 amps draw at that line voltage would be 242 watts.  The two-amp fuse I had in the Stereo Theater amp did its job.  This value gives a little headroom for warming up cold tubes.  I used a 1-amp fuse in the smaller stereos.  I have a two-amp fuse in each amp on the Concert Grand.  I put a one-amp fuse in the tuner power supply on the CG.  The Imperial has a two amp fuse.  The Symphony has a two-amp fuse.  I put a 1-amp in the little GE radio I redid for a neighbor.  I am putting one-amp fuses in the little GE stereos I have.  Anybody who rebuilds a device with a power transformer without putting a fuse in the primary of the PT is on a fool's errand as far as I'm concerned.  This is the second time in recent history I know for sure of a fuse saving a power transformer. 

Since I received my watt meter for my birthday, I don't know what it cost.  The ones I priced were in the $20-$30 range.  They are worth their weight in gold.  It is easy to tell how much power something uses to figure how big a fuse to use.  I would highly recommend such a device if one is working with devices that  use more than about 75 watts of power.  Under that, a dim bulb would be just fine.  A watt meter will not limit current like a dim bulb, but it does not need to.  You can pull the plug when you see wattage becoming excessive. 

I'm not going to pat myself on the back precipitously.  I want to run thru a couple warming and cooling off cycles to be sure a shorted dial bulb is the only issue.  I'm not out of the woods yet.

As far as inrush current is concerned, it's interesting to watch the rectifier starting to conduct.  The Stereo Theater will peak at about 176 watts while the rectifier is starting to conduct and the filter caps are charging.  Then the wattage falls a bit, rises a bit, then settles down to around 155 watts, sometimes a watt or two more.   

The new bulbs I put in the tuner were from Radio Daze.  I bought a couple boxes of #47 bulbs specifically for this project.  I'm a bit hesitant using more of them.  I may go to NAPA and pay the big money ($3) for ten Sylvania bulbs.  What say you all about this?  Anybody else had experience with bad bulbs lately?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on September 10, 2019, 08:08:16 PM
First congrats on the simple fix!  :)  Good thoughts that does the trick.  ;D  Second, your formula is what I use to figure the size of a fuse.  As I have said many times before on the forum installing a fuse saved my butt, and my PT.  :) :)  I install a fuse in just about everything I rebuild.

There are good, better, and best when it comes to bulbs.  Most today come from China, but even China has ultra cheap, and better quality.  I have found, and this comes from experience in the auto industry, that brand names like Sylvania, and others, are usually better than say a store brand, or no name brand.  I can remember when GM started getting their replacement bulbs from China, they were the cheap ones because the bean counters were trying to save money.  :o  It backfired....Replacement parts, if installed by a dealer have a warranty including labor.  We were replacing those brand new bulbs left and right within a month of installation, and GM was paying.  All car companies hate paying warranty claims, so needless to say they changed  suppliers very quickly.  ::) ;) :)

Good luck, and I hope you can move on to the TV.  ;) ;) ;) :)

Bill


 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 10, 2019, 08:27:22 PM
I appreciate the input about bulbs.  This may be one time that being cheap cost me in the long run.   ::)

I believe you understand how it feels to work on something, get it running and actually use it for a reasonable amount of time, then have it shoot craps without warning or without apparent reason.  That is not a good feeling.  I thought it was dead for good and that I had killed it.  My method of troubleshooting was not very scientific.   ;)

I'll make sure the ST still wants to work then I'll move on to the TV. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on September 10, 2019, 08:40:25 PM
I thought your method of trouble shooting was very much in a logical order.  End result, you found the problem, and it was not your fault.  Well maybe, you bought cheap bulbs.  ::) ::) ::) ;) ;) :) ;D ;D  Sorry, I couldn't resist.  ;) :)  Remember I'm cheap too.  :o ::)

Bill

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 10, 2019, 08:46:34 PM
A simple fix.  Perhaps TOO simple.  It took all day, since I neglected to post how much I had to take apart to get the 6CY5 tube back in the tuner.  It came out pretty easy.  The TV should not have anything to do, power wise, with the tuner nor with the amp. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on September 11, 2019, 01:07:10 AM
             Good for you Greg. You found that bad pilot light a lot, lot faster than I would have, that's for sure. I'm the guy that took a cylinder head off of a Triumph TR-4 engine because cylinders 3 and 4 weren't firing and I was convinced it had a blown head gasket. If I had only removed the air cleaners to the twin SU carburetors first, I would have seen that an aftermarket foam rubber air cleaner element had gotten sucked into a carburetor throat and was flooding cylinders  3 and 4.  I was "trying to save time" (oh, the irony !!)  by leaving the manifold and carbs and air cleaners  attached to each other.
            Just last week, suddenly called back to work,  I had a General Radio VTVM with 2 fuses, one in each AC line wire but not blown,  not even lighting its pilot lamp or the 6 volt tube filaments, and yet it had + and - 250 VDC and the voltage regulator glow tubes were lit.  It smelled a little like heated metal when it was on for a while, but the panel meter refused to move with zero adjustment. But the power transformer must've been good, at least it had DC power supplies up. I never did find out why the pilot lamp and 6 volt tube filaments wouldn't light as we had no time to fix it. We just used a DVM instead.
              It took me forever to realize it wasn't the line cord, fuse, on-off switch, etc. Maybe it had an open filament winding ?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 11, 2019, 08:55:18 AM
While I certainly appreciate the kind words, let's reserve our congratulations and back patting until we see that TV screen light.  I'm not 100% convinced we have heard the rest of the story on this thing yet.  I was putzing with the TV controls yesterday when all hell broke loose.  I remember I turned the function switch to "TV", maybe heard a hum (?), then everything went silent.  A pilot light bulb could have caused the hum, since it is in the filament circuit.  I have never had a pilot light bulb fail like that.  Usually they just don't work when you turn them on, or they pop when you turn them on.  I have checked those bulbs with an ohmmeter and they check like normal, good bulbs.  I know, though, that the fuse in the amp will do its job.  There is no power shared between the amp and the TV chassis.  The function switch serves as the power switch for the TV.

If I could figure out the specs on the power transformer in the amp, I'd entertain the notion of replacing it anyway.  It is too small for the opening in the chassis and looks odd.  And a transformer designed to run on 125 volts with high temperature insulation would be a benefit.  Surely, I could find a good, heavy power transformer for under $100.  All that is given on the PT in Sams and in the Magnavox literature I have is a part number.  Lot of good that does 60 years after it has become obsolete.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 11, 2019, 07:37:48 PM
Now I'm stuck...... ::) :-[ :-\ ;)

I tried the TV again.  And had a giant fail again.  I believe this problem is my doing.

This is a long story, and I apologize if this is long winded.  There is an interlock block where the power comes into the instrument.  The power cord has an interlock on it, typical of TV power cords.  There is a circuit breaker that goes to the TV chassis and a double black wire that goes to the plug for the amp located on the TV chassis.  The wire for the amp goes around the circuit breaker.  I was under the impression that the TV was powered thru the circuit breaker and the amp was powered around the circuit breaker.  I do not have a diagram or literature on this portion of the Stereo Theater.  Now I'm beginning to believe that the circuit breaker only protects the high voltage section of the TV chassis, while the line voltage, or low voltage for the TV chassis runs thru the amp chassis.  The stereo will play just fine until I turn on the TV.  When the wattage gets over 200, it pops the 2-amp fuse in the amp chassis.  I need to find the wire that powers the TV chassis and route it in front of the fuse.  I put the fuse in one side of the line, and it's not enough to protect the amp, yet power up the TV chassis.  I don't want to have to pull the radio tuner to chase those wires.  I'm open to input, here, guys.  I believe, for the purposes of testing, I'll replace the fuse in the amp, make sure the stereo still works, then power the TV chassis up separately.  I can unplug the TV chassis from the radio tuner and power it with an extension cord. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on September 11, 2019, 07:49:00 PM
I can't recall seeing a circuit breaker on consumer goods in anything but  a primary circuit.  I doubt it's in a HV circuit.  In places like that they would likely have a non-user-serviceable device, one requiring the service guy to come out and fix the underlying problem.  But those are just semi-ignorant guesses. 

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 11, 2019, 08:01:34 PM
I remember reading somewhere that the circuit breaker in TV sets only protected the high voltage section of the TV.  There is a fuse usually found in the low voltage section of the TV for the filaments and that.  I don't see a fuse in this one.  There was no fuse in the amp.  I believe I may have a plan, borne out of desperation.  I'm going to assume the PT for the amp does not power the TV.  The PT on the TV chassis is twice the size of the one in the amp.  The TV chassis has its own solid state rectifiers and filter components.  My plan is to restore the amp chassis like it was before I put the fuse in.  Take the fuse completely out of the line.  The line cord goes to a terminal strip where the wires for the PT are connected.  Then I'll break a connection between that terminal strip and the primary wires and insert the fuse there.  I'll still be protecting the PT with the fuse, but I'll also be able to power the TV chassis, being that it is now around or ahead of the fuse.  I need a complete schematic for the Stereo Theater in the worst way, but I'm told such an animal does not exist. 

Another point to ponder.  The TV chassis plugs into the tuner chassis with a regular line plug.  I figured one side of that line cord was hot, the function switch in the tuner completed the circuit.  Apparently that is not the case.  This is what threw me off, guessing how Magnavox wired this thing.  The amp powers the tuner, but there has to be an extra wire from the power cord on the amp that powers up the low voltage in the TV.  Strange......

How far off am I?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 11, 2019, 08:48:36 PM
The copy of the schematic for the C36-20 chassis I have is smudged.  That said, I don't see any relationship between the power in the TV chassis to the amp chassis.  This Stereo Theater has a replacement power transformer in there now.  The TV has not worked in who-knows-how-many years.  I have to wonder if the problem I'm having has been there for eons.  Whatever burned up the original transformer may still be there, and would have taken this one out had it not been for the fuse I put in.  The amp does power the tuner chassis.  The TV chassis plugs into the tuner chassis.  What does the fuse in the amp chassis power cord have to do with the TV chassis?   ::) :-[ :-\ :o

I'm thinking out loud here, so please bear with me.  Could this be an issue with the remote control as well?  I believe my first step is to disconnect the TV completely from the tuner, then power up the TV separately using the wattmeter and an extension cord.  This will give me an indication if the TV has a problem.  Then, with the TV completely disconnected from the tuner (power cord and audio cable) see if the fuse blows in the amp when I turn the function switch to "TV".  (I still have not replaced the three dial light bulbs in the tuner, so they are not causing a problem).  The stereo works just fine until I turn the function switch to "TV".  There is a switch to turn the remote control amp off and on.  It has never been "on" since I have been working with this thing.  Everything in this Stereo Theater is powered by the amp chassis except the TV chassis, if I'm reading right.  I need to order a truck load of 2-amp fuses and I need to see if I can obtain some more service literature on this Stereo Theater. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: SeniorSteve on September 12, 2019, 08:35:54 AM
If the audio portion of the stereo theater works correctly and the fuse blows only after you turn on the tv, it means that the fuse is trying to "protect" both the audio amp and tv.  Check your wiring to make sure the fuse is wired on the primary of the transformer on the audio amp only.  The best way to do this is to disconnect one lead of the primary of the transformer and connect it to one side of the fuse, then the other side of the fuse would go to the point where you disconnected the transformer lead.  My gut feeling is the added fuse is not protecting just the power transformer on the amplifier, the TV current is going through it as well.  With all of the work you have put into this, I hate to have you get discouraged.

Steve
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 12, 2019, 10:17:58 AM
I'm not discouraged, I'm just STUCK.  I can't go much further without more information on this thing.  This is part of restoration.  This is like getting a '56 Packard into the shop with the torsion bars all the way down.  Getting it UP so I could fix it was the bigger task.....

I don't have any information at all on the radio tuner.  I have factory documentation for the C36 series TV chassis, and it has served me well up to this point.  Now I need specific documentation on the C36-20 chassis.  And it would be helpful to have some type of documentation on this Stereo Theater in its entirety, something I have not yet found. 

Steve, like you, I wondered if there was some power supply for the TV chassis that ran thru the amp chassis.  At this point, subject to change, I don't think that is the case.  The TV chassis appears to be powered thru the circuit breaker on the interlock board.  The "power cord" that goes to the tuner from the TV chassis appears, again subject to change, to be nothing more than a convenient way to provide a switch for power to the TV chassis.  Then there is the single wire with an RCA jack that carries audio from the TV chassis to the radio tuner.  The notes I made on the tuner do not indicate that I noticed anything amiss.  I remember seeing a switch ganged to the function switch in something I've worked on, perhaps this chassis.  And that would make sense.  My theory at this point is that something is shorting or backfeeding the 6-volt winding in the power transformer in the amp chassis, causing the fuse to blow.  Since there was no fuse in this amp when I got it, I'm almost certain that this exact issue I am chasing is what toasted the original power transformer.  I'll bet a TV repair shop in Detroit found the transformer bad, found the short and either wanted too much to repair it, or did not figure something "Old" was worth putting the money into and advised their customer likewise.  The power transformer was replaced so the stereo would work, and the TV was abandoned.  There were a myriad of issues with the TV chassis, so I wonder if the issues with the TV chassis caused this issue or if the two are just coincidence.  The issue I had with dial light bulbs should have given me a clue.  I have since tried these three bulbs in another device and have found they are good.  The wiring for the bulbs is what I suspect of somehow being the problem.  When the function switch is turned to "TV" something backfeeds or shorts the wiring to the dial lights and pops the fuse in the amp chassis?  How much weirder of a problem could one imagine?

I believe I will change the orientation of the fuse.  Do like Steve suggested.  That will do the same job of protecting the transformer and should eliminate any possibility that I'm wrong about how power goes to the TV.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 12, 2019, 02:25:45 PM
I'll re-orient the fuse, but I'm not sure it's the problem.  The extra wire is for the record player motor.  It goes to pin 5 of the Molex connector.  The switch I remembered that was ganged to the function switch is also for the record player motor.  I'm back to chasing a legitimate short.  I'll see if I can get some information on the 77-series tuner and go from there.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: SeniorSteve on September 12, 2019, 03:43:24 PM
If the TV is powered by the plug on the tuner, pull that plug from the TV to the tuner and see if the fuse blows when you select the TV position, it shouldn't.  This will tell you if the TV power is being run through the fuse.  If indeed you have a short, the fuse will blow anyway.  I'm trying to figure out logically how to determine if the TV power is being run through the fuse.  Keep reporting and I'll think of another way to test.

Steve
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: TC Chris on September 12, 2019, 07:09:31 PM
Here's another suggestion.  Doesn't all the power to the TV chassis have to go through its own power transformer?  Why not just disconnect the TV power transformer primary and wire a cord to it, with maybe a switch and fuse, and power it up independently?  That would be a way of determining if the video circuits were doing anything, or perhaps if there were some internal TV-only short.  It's possible that something could have got wired just exactly wrong. Not that I've ever done anything dumb like that, of course....

Chris Campbell
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 12, 2019, 10:34:46 PM
The plug from the TV to the tuner has got to be to the switch.  The primary of the PT for the TV chassis gets its power thru the circuit breaker at the interlock.  I need to get more 2-amp fuses before I can test much else.  I don't want to use a larger fuse.  Then I'll unplug the wire from the TV to tuner and see if the fuse holds.  If it does, I'll short-check the TV chassis.  When I went thru it last winter, all the resistances checked per the schematic.  If the fuse blows with the TV disconnected from the tuner, something is going on in the tuner, it would seem to me.  How the amp chassis has anything to do with the power supply of the TV chassis is still a mystery.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 13, 2019, 11:06:49 AM
I have been tracing wires this morning until my eyes are gonna bleed.   ::)

I MAY have found a possible connection between the TV power and the amp chassis.  THE REMOTE CONTROL!  The amp chassis powers the remote control.  And since the remote control chassis is solid state, and by trying to follow the wires best I can, I believe the remote control is powered by a SECOND six volt tap on the power transformer in the amp chassis.  The amp chassis schematic shows a second six volt tap that powers the 6EU7 filament separately from the rest of the filaments in the tuner.  I suspect one of the  six volt taps is powering the remote control chassis.  Being that it is solid state, we wouldn't need high voltage in the remote.  (I am searching for a schematic that may not exist for this thing!) Something as simple as a set of stuck points in the remote control may be causing a short in TV power.  I need to divorce the TV chassis completely from the stereo in order to test it.  Then I need to try to separate the remote control from the stereo, then test the stereo and the TV together, if the TV works okay separately.  There is an on-off switch for the remote control on the rear of the cabinet, next to the interlock board.  The remote has been turned off, and still is.  The audio goes thru the remote control chassis and thru this switch.  The remote only controls TV functions, on-off, volume in three steps, and channel selector.  While it does not change stations in the tuner, nor does it work with the record changer, it appears to me that the remote will turn off power and change volume in the tuner, since the remote works with the tuner, not the TV.  So, if there was a short somewhere in the remote chassis, that would be in series with the tuner and TV.  Wow!

For all you out there in the cloud who are following this Stereo Theater restoration, and to those on this forum who are following it and have given so generously of their time and talent, I thank you for your interest and for your patience.  This is new territory for me.  And, at least for this part, I'm flying blind without the proper documentation.  Anyone who has information on this instrument and would be kind enough to make that information available, it would be greatly appreciated.  I'll get this thing going, eventually.  I may have to run every single wire in it to figure out how it works, but I'll get it.   
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 13, 2019, 11:43:20 AM
I see one version of the remote control chassis schematic that has 110 volts to it and shows a power transformer on the remote chassis.  That would shoot my theory of the amp chassis powering the remote chassis via the amp power transformer, but how do they get the 110 volts to the remote chassis? 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on September 14, 2019, 02:56:37 PM
           Just out of curiosity I looked at the primary side switching of some Magnavox chassis of the late 50s and early 60s under the downloads section on this forum. I was checking for fuses, circuit breakers, switches, remote control relays etc. A TV chassis 36 I think, had a circuit breaker in series with the transformer primary, along with the on-off switch, a length of # 24 wire in series with the filament winding as a filament circuit fuse, and a 5 ohm 10 watt resistor in series with the secondary winding to the silicon diodes and filter capacitors of the 280 VDC.  There were no other fuses or limiting resistors in series with the damper tube or horizontal output tube or the "Boost" voltage. The circuit breaker looked like it was next to the power cord interlock and would be resettable without taking the back off the set.
               What I was wondering, Greg is does it look like Magnavox took this chassis, changed only the location of the tuner and controls, added the motors for remote channel selection and led the audio output of the FM detector off the chassis to remote volume motor circuits elsewhere and changed almost nothing else, including fusing and circuit breaker ?  This particular schematic shows only 19 inch and 23 inch CRTs on it, but if the 27 inch CRT has the same deflection angle, they could use the same yoke and deflection circuits, maybe a higher CRT anode high voltage and current. I'm assuming you could get the ST with different size picture tubes and also that remote control wasn't standard in all STs.
            Well then I looked at the schematic for the 1958 or so Concert Grand, with remote control and separate amp and tuner and remote chassis. I see that nothing in this CG looks anything like your ST but I figured hat the schematics for the remote control would at least indicate how Magnavox grafted in the  Remote chassis and maybe they adapted the old circuits as best they could for the ST.  It was the most confusing thing I've ever seen. I never was able to figure out what controlled what in the 117 volt primary circuits to the radio chassis and remote chassis and the paths for the audio signal is just as confusing. I truly hope you can find the exact wiring schematic for your particular ST but I bet they were changing things on the fly to correct problems or complaints. 
          It looked like the remote chassis, in this CG model, at least, had its own power transformer for DC plate voltages and filaments to stay active even when everything else was shut off, but with no fusing at all, which is scary because this remote chassis may stay powered up 24 hours a day if the owner didn't bother using a master off switch, wherever that was. and however it might be labelled. There was a 24 VAC winding that looks like it powered some relays and some selector motors for remote control rotation of pots, and there looked like other relays that wouldn't be in your ST that were powered by DC plate voltage in the FM-AM chassis for radio station searching, and another 117 volt relay in the record changer for record reject.
          I don't think any fuse, even the slow-blow ones, can handle the kind of turn-on surge currents that the cold tube filaments, and the super low resistance of power silicon rectifier diodes charging large electrolytic filter caps. would draw. That is probably why they went to the thermal circuit breakers with manual reset. Those circuit breakers were their own surge limiters and can keep from tripping  for many seconds if they make the thermal element large enough, it just has to trip faster than the transformer would overheat.
             If your TV horizontal output stage is wired like the one in the download, there is a large resistor in series with the screen grid of the horizontal output tube going to 280 VDC and it looks like it lowers the screen grid voltage to 140 volts or so. That should protect the tube and HO transformer if the oscillator stopped working or if you were bringing the voltage up slow on a variac. The older TV sets that connected  the screen grids directly to DC voltage without the voltage dropping resistor are the ones that will melt down if the horizontal oscillator tube decides to burn out.  Those were the ones that usually had separate fuses for the horizontal circuit--they had to.
               
                 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 14, 2019, 03:39:40 PM
As far as I have been able to determine, the generic C36 series TV chassis schematic will work for 99% of this TV chassis.  The change is in the power supply.  And most of that difference is ahead of the circuit breaker to the TV chassis.  I have a "close" schematic for the TV chassis, but not an "exact."  I also have a "close" schematic for the remote control.  The circuit breaker at first appeared as if it received power at the interlock.  I have found that to not be the case.  At this point, it appears the power cord coming out of the tuner may actually provide line voltage to the power transformer on the TV chassis.  How line voltage gets to the tuner is the next question.  The logical assumption would be that the tuner gets line voltage via the amp chassis.  I have not found any extra wires in the amp chassis to confirm this.  Only one for the phono motor.  There appears to be two ganged switches ganged to the function switch in the tuner.  Is it possible that the wire that supplies line voltage to the phono motor also provides line voltage to the TV chassis?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 14, 2019, 05:57:16 PM
I'm back to having the stereo playing again.  I'm not sure I know anymore than I did.  I made some notes on schematics about what I found and about the fuse in the amp transformer primary.  There are several switches and micro switches in this thing.  I count four switches to control the TV alone.  Five if you count the function switch, which controls audio.  The wiring appears to be in beautiful condition.  I'm grateful for Magnavox's brightly colored plastic wiring without stripes or dots.  Next is to verify I have eliminated the issue with dial lamps, then see if the TV chassis will work.  I've about had all the fun I can stand for one day.  Well, maybe a couple more little things...... ::) ;) :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: 19and41 on September 14, 2019, 09:45:43 PM
I read back through the saga to today.  Sorry about the trouble you're having.  I wish there were more dab hands with CRT televisions as there once were, to seek advice from.  Greg, you've done valiant work in getting the set to this point.  I have some long life #47 's available should you need them.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 14, 2019, 10:44:18 PM
It's good to hear from you and thank you for the kind words, Rex.  I may finally have this down to just a couple areas of concern.  Seeing the CRT light with a raster and some noise in the audio would be "magnificent" about now.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 15, 2019, 11:49:14 AM
Success!!   :) :) :) :)

Well, maybe partial success might be a better term.  I have most of a TV set.  I have no shorts, no arching, no red plating.  I have a nice, full screen.  It appears to have a bright picture tube.  The entire Stereo Theater pulls 301.85 watts without the record player motor on.  I have no TV audio, just a hum.  I see hash in the raster, but I don't know for sure if the tuner and IF sections are working.  The display is best described as "squiggly".  It was unstable horizonatally when the display came up, and I seemed to be able to adjust that out.  I'm guessing I have both vertical and horizonatal unstable or I have a dirty control.  There is nothing connected to the antenna terminals.  Maybe some kind of signal thru the tuner might be what I need now.  But, this is progress.  Now we get to sort the TV.   ::) :-\ :-[ ;) :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on September 15, 2019, 11:55:12 AM
Congrats Greg!   It's been a long time coming but I knew you could do it.  So what was the reason it was blowing the amp fuse?

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on September 15, 2019, 01:33:59 PM
   Sounds like you are almost there if you have a decent raster.
          A 60s Zenith B&W I looked at years ago had an open 3.9 MegOhm resistor from +Dc voltage too the AGC line. The set would play at first, then slowly go to no sound and then blank white raster with no snow. I guess that 3.9 Meg resistor from +DC to the AGC line was there to bleed off a buildup of voltage that would shut down the RF and IF stages. Your set looks like it has that "Keyed AGC" circuit that somehow turns large pulses from the horizontal output transformer and sync pulses from the video signal into small negative going AGC voltage, but I never understood how it did it, especially how it opened the gain of the set way up when there was no video signal to receive.
         With the set operating, put a DC voltmeter across that 3.9 Meg resistor and if you get snow and rushing noise back, you will know that resistor is open. I don't think you can measure it in the circuit with power off because there are too many bypass paths giving false readings. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: 19and41 on September 15, 2019, 04:25:46 PM
That's great!  Didn't you get a pattern generator sometime back?  If not you will probably need a digital to analog converter.  I have one from the government giveaway unopened, should you need one.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 16, 2019, 12:17:14 AM
It's been a long day and I'm beat.  I'll just say this.  And I promise pictures and more information in the morning.  The short in the TV was not an actual short.  I placed the fuse in the wrong spot.  I was trying to power 300 watts with a 2-amp fuse.  Verifying all this was a grand adventure, one worthy of sharing.  My next job is to gain information and test equipment in order to troubleshoot the "white screen" issue.  But, this is progress and I am sure grateful to all you guys who pitched in with your two cents.  This project would not have come this far without all of you.  BTW, we are 75% done......... :) :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on September 16, 2019, 07:38:15 AM
 :) :) :) :) :) :) :) :) :) ;D ;D ;D ;D ;D ;D ;D

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 16, 2019, 12:06:38 PM
I had an eye doctor's appointment this morning I had forgotten about.  I'll have to go back on my word about posting this morning.  I'll try to get it done later this evening.  Thanks for your interest.   :) :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Harbourmaster on September 16, 2019, 05:24:30 PM
An old VCR or DVD player would actually be about the simplest video source to hook up for testing.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 16, 2019, 10:53:51 PM
It's been another long day.  I'm going to hit the hay and start again in the morning.  Ken, I have a VCR I can use if I can actually get a raster.  I'm not going anywhere with just a white screen and no audio.  My ultimate goal is to find a B&K Analyzer, either a 1076 or a 1077.  My understanding is they are simple to use and effective for TV repair.  I have nothing now in the way of TV testing equipment or signal generators for TV.  I'm guessing that if I get this one going, it won't be my last TV project.  The problem with finding an Analyzer is that shipping is worth more than the device. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 17, 2019, 09:19:01 AM
I'm in the market for a new camera.  I suppose cameras are now obsolete and I need to use my phone.  This one has been good for several years, but it's been dropped and knocked around too much.  The batteries won't stay in without duct tape.  But, as they say, a picture, even a fuzzy picture, speaks louder than words..... ::) ;) :)

The black bar in the TV screen is not there in real life.  That is some kind of reaction between the sweep in the TV and my camera.  See that cute little channel indicator in the corner of the picture tube mask?  I think that thing is neat.  I also like my new wattmeter.  I don't know how I ever got along without one.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: 19and41 on September 17, 2019, 09:52:45 AM
That pic looks like the alignments are off.  I would imagine you could get an image with a good video source.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 17, 2019, 01:34:51 PM
Which alignments do you believe would be off?  The "squigglies" kind of swim back and forth headed toward the right of the screen.  Do you mean "adjustments" rather than "alignments"?  Adjustments I might be able to do.  I'll need more equipment and knowledge than I have now to do an alignment.  The hum in the audio may have been self-inflicted.  I tied the power cord, wires from the tuner and the audio cable from the TV all in a neat bundle with wire ties.  Perhaps making those wires messy again will cure the hum in the TV audio.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on September 17, 2019, 06:52:20 PM
A picture, or snow, or what every you want to call it is outstanding.  It even fills the whole screen.  :) :)   Did you separate the wires yet to see if the hum goes away?  I think I would try a VCR just for the heck of it.  It might surprise you with a real picture.   ;D ;D

Bill

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 17, 2019, 09:02:44 PM
It surprised me by having a totally dark picture tube!   >:( ??? ::) :-[ :-\

Both the vertical and horizontal are unstable.  I have no audio.  I DID have a raster, but no picture.  Now no raster.  The controls don't seem to want to do much.  The brightness control never has had much affect, but this chassis has Magnalux that controls brightness.  The upper controls, horiz., vert., brightness, and contrast were fairly dirty and scratchy.  I was dinking with them, when the picture flashed a couple times then went dark.  It flashed a couple more times, then nothing.  The wattage is the same, it did not go up or down.  I can hear the vertical oscillator running.  The high voltage never has made any noise.  No tubes are red plating.  I reckon I need to see if I have high voltage.  This thing is going to fight me to the bitter end.  I didn't notice whether the filament in the picture tube was still lit or not. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on September 17, 2019, 09:27:12 PM
             Those squiggles in the picture are probably due to the horizontal and vertical oscillators free-running since with no TV stations tuned in there are no video sync pulses to synchronize to. Having a nice bright raster is great because now you know that all your power supply and sweep section repairs were successful and in addition it means that the horizontal oscillator is free-running very close to the right frequency. If you turn the horizontal hold control a little CW or CCW, you should see the brightness go up and down like peaking a tuned circuit. That dark bar in the picture is probably from the camera shutter catching the picture in the middle of a vertical scan. 
              If you have a VCR or a DVD player with a video output you might inject its video onto the control grid of the 6BL8 (?) video amplifier of the TV chassis and your screen should have a picture on it. ( O Happy Moment !! )  That test will bypass your RF tuner and all 3 of the video IF stages, but you will at least know that the contrast control and wiring around the CRT socket is good.
           I think you have the right idea cleaning up the craziness of the wiring in that beast but don't lace things too tightly or permanently because you may wind up separating certain wires later--especially heavy current filament wiring from audio cables. I actually saw an article talking about the advantages of "sloppy" wiring, it was officially titled "rats nest" wiring. It was used in modules that were to be potted which was good because no-one had to see it.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on September 17, 2019, 09:32:33 PM
    Oops, just saw your new post after I posted mine. Hopefully your horizontal hold control has a bad spot in it. Hope its something easily fixed.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 17, 2019, 09:55:33 PM
I was in the process of connected the VCR when I started having an issue.  Connecting the VCR had nothing to do with it, because I didn't get it connected.  If I understand right, I shouldn't run the TV too long with a black screen.  I guess I'll check tubes and make sure I did not lose B+ for some reason.  I still have the same wattage draw as before, so I would think that I still had B+.  I'll test the horizontal oscillator tube, the damper tube, and the HO tube to see if they are still good.  I've never had sound. 

I was posting when you were posting.  Sorry.  Remember, Ed, this is the first TV I have ever messed with outside of dusting and changing tubes.  I am the rawest of amateurs.  I see the horizontal hold control (R3) as being a 50K ohm control that is in the grid circuit of the 6FQ7/6CG7 horizontal multi-vibrator tube, pin 7.  The brightness control, (R4) a 200K ohm pot, goes to pin 6 of the CRT.  I'll check those and the tubes I mentioned then go from there.  It acted like a dirty control to me, but what do I know. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on September 17, 2019, 10:15:56 PM
        Good luck. I'm hoping the horizontal hold control just hit a dead spot. If the control is turned too far away from 15,750 Hz oscillator frequency, there won't be enough voltage to light the 1B3 HV rectifier filament as the HOT is kind of resonant tuned. Also, in the chassis 36 I've seen, the vertical oscillator runs on the horizontal Boost DC voltage, about 450 VDC  so if you have that boost voltage, you probably have sweep too. Your HV rectifier tube may have decided to die which would give a dark screen with only a slight lowering of wattage.  Just about the only way to measure it is to remove the tube and ohm out its filament. The filamenet glow is barely visible even in a dark room.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 17, 2019, 10:24:09 PM
Is it normal for a horizontal hold control to "hit a dead spot" as a matter of course?  How long can I safely run the set powered up with a black screen?  I've read where that is not a good thing.

The schematic gives -15 volts on the grid of the horizontal multivibrator.  I'm guessing the horizontal hold control biases the tube and this makes the high voltage run?  Am I close?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on September 18, 2019, 06:03:29 AM
Me, being the real dummy here, is it possible that the controls you were monkeying with still need more cleaning? 

Bill
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on September 18, 2019, 08:02:35 AM
          The schematic I'm looking at doesn't give a DC voltage on the 6CG7 grid pin 7 but it does give negative 30 volts DC on the grid of the horizontal output tube. I hope the chassis 36 is similar to yours.
          Well, the horizontal hold pot can get a dead spot on it if it is never adjusted in its years of operation, which is likely if the owners weren't knob twiddlers. The AFC dual diodes make the circuit like an FM tuner with AFC always on and only one radio station on the dial. The pot wiper eventually makes a bare spot on the one area the control is left sitting on. Just like a Magnavox console with spindly legs will eventually grind the carpet under the legs to nothing is not moved for 50 years. The rest of the pot gets 50 years of dust and oxidation on it without the self-cleaning action of occasional adjustment.
           Since the oscillator is free running with no TV station to synchronize to, only a little adjustment of the pot will send the frequency up and down over a super wide range. If the frequency is far enough away from 15,750 kHZ the various capacitors in parallel with the yoke coils and transformer windings will not be near resonance any more and there may not be enough 15 kHz AC to light the filament of the 1B3 HV rectifier tube and you will have low or no high voltage, and a dark screen even though your horizontal multi-vibrator is oscillating OK. A set with a non-lighting HV rectifier tube is not being hurt even though it has a black screen.
        Maybe check the DC voltage at the horizontal out tube grid, which the schematic I am looking at shows negative 30 VDC. If you have that negative 30 volts on the grid you should be able to leave the seet powered up while troubleshooting even with a dark screen. There is a rare failure of the HV rectifier tube where the filament sags and rests against the plate, which then puts the high AC high voltage across the filter capacitor composed of the aquadag coating on the inside and outside glass of the back of he CRT. But that failure would cause your watt meter to read higher than otherwise because that capacitor is a heavy load on the transformer.
          The horizontal control indirectly generates the HV by adjusting the RC time constant in the multivibrator to put its free running frequency close to 15,750 Hz, and then the AFC diodes and circuit lock it into the exact TV station frequency. If you have your negative 30 VDC on the output tube's grid you might vary the pot slowly back and forth and see if the raster comes back but it has to be close to the right frequency for a few seconds to give the 1B3 filament time to light up. But if you don't have that negative 30 VDC on that grid don't leave the set on for too long. Even with the large resistor in the screen grid circuit limiting the screen voltage and current, the tube is still derawing a heavier than normal DC current without that negative 30 VDC on the control grid.
            The bias on the output tube grid results from the grid-cathode acting like an AM detector diode like in an AM radio. It's presence means that a large AC voltage is capacitor coupled to the grid and that would only be there if the horizontal multi-vibrator is functioning, at least at the right voltage but not necessarily the right frequency.  To get the HV on the CRT you need the right voltage and close to the right frequency.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 18, 2019, 08:39:16 AM
The picture tube in this TV has a wafer socket on it.  The only key there is on it is a dimple in the glass.  I dreamed last night that I got the plug one pin off on the CRT.  Would that be possible in real life, and what would the effect of that be? 

I'll check the horizontal hold.  Would that control be open if it had a bad spot in it, or only open in the bad spot, yet good elsewise? 

The schematic I have shows -15 on pin 7 of the 6CG7.  The HV rectifier is a 1K3, and it was new when I worked on the chassis, but not since the failure.  The C36 chassis are very similar, the main difference being the audio circuits and the LV power supply.  You have to watch for the notation "some Theater models".  I own a "Some Theater" model.  This thing also does not have audio.  I read somewhere that if you have no picture and no sound, a certain tube might be the cause.  6GC5, maybe? 

First thing I'm going to do is to make sure the CRT is lighting.  Then I'll test tubes.  Then I'll check the controls. Then I'll punt.  Thanks, Ed.  I'm going to need a hand with this one.   ;) :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: 19and41 on September 18, 2019, 08:53:29 AM
Those adjustment controls have rested for a long time at a specific setting, with tar, nicotine and other pollutants covering the rest of the controls surfaces.  If unsure if there is a bad spot, you could disconnect and do a resistance and continuity check and clean of them.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 18, 2019, 09:37:10 AM
That's next.  I'll clean and test all four of the "operator available" controls and see what that does.  I have seen volume controls completely kill a radio, so I assume the controls on this TV could do the same?  I understand that if the horizontal oscillator is running too far off frequency, it will kill the HV rectifier.  The horizontal hold seems to be dead over the full range of the control. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 18, 2019, 10:51:26 AM
I see there is a horizontal frequency control in the cathode circuit of the 6CG7.  There is a procedure listed in the Magnavox version of the C36 chassis schematic for adjusting this control.  It says to turn the horizontal hold control to mid-way, then adjust the horizontal frequency control.  Could it be possible that after I changed components in the horizontal circuit, caps, tubes, etc., that the horizontal is running so far off-frequency that it has killed the HV rectifier?  Before the screen went black, the horizontal hold control was not having much effect.  Now, I need to figure out a way to troubleshoot this.  How do I determine which control is the cutprit?  That horizontal frequency control could also be dirty or have tinwhiskers.  Horizontal width is a coil, L22, not a pot?  There is a width control on the chassis.  Where am I overlooking it on the schematic?....... :-[
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 19, 2019, 12:48:43 PM
I have the raster back!!   :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :)

I have no idea what I did to fix it.  First thing I'm gonna say is that I got two pieces of REALLY BAD advice on another forum.  Those were not to clean the controls, lest you wreck them and to remove all the unused pins from the new damper tube socket.  This morning, I washed the wadding out of the controls with brake cleaner.  Then I gave them a good dousing with WD-40.  The resistance of the contrast, brightness, horiz. hold and vert. hold controls were all over the place.  I really believe the brightness control was the one that killed the picture tube.  It sent the tube to full darkness.  It showed shorted to ground when I first checked it.  It is 200K ohm when it is right.  The damper tube was REALLY loose in its socket.  I tightened the pins best I could.  If I can't find the pins I removed from this socket (I think I saved them), then I'll get another socket and leave the unused pins in this time.  The damper tube lays on its side, not a very good idea to begin with.  The extra pins help stabilize the tube.  I still don't have any audio and the horizontal is unstable.  I understand why the TV guys call these things "Maggotbox".  This is not a very good TV.  I don't believe I'll ever get this thing where it will be dependable for frequent use.  If I can get it good enough for OCCASIONAL use, that's all I can hope for.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 19, 2019, 03:03:46 PM
My next foray is into the video amplifier stage.  This is where audio and video are separated.  I can see in the picture tube a "scratching" or disturbance when I change TV channels, but I can't hear that.  I may have an issue in the tuner, but I should be able to hear that noise between channels.  I am almost done troubleshooting until I get a test socket....... :-[
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 19, 2019, 04:35:53 PM
I have absolutely NO audio going from the TV chassis to the tuner.  I can't even get noise when I wiggle tubes.  I'm about 90% convinced I need to troubleshoot the tuner next.  I have no picture and no audio.  Connecting the VCR does nothing.  I'm getting retrace lines, and I can't tell if the horizontal is finally stable or not.  I have an extra 20 watts draw on the line now.  The picture tube is brighter and the brightness control actually works.  I can't really tell anything about the contrast control working at this point.  I'm really glad to see the picture tube lighting.......... ;) :) :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Harbourmaster on September 19, 2019, 05:27:58 PM
One small victory at a time...   :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on September 19, 2019, 07:20:48 PM
           That is great news, Greg. It's a pleasure to try and help you get this massive ST going because you simply never give up !!.   I will not even try and comment on the kind of advice you have been getting from those "other" forums. Stick with us ! 
           If that damper tube socket is good and clean, and it must be if you took it to pieces enough to get the unused pins out, I wouldn't replace it unless you can find a socket made for another damper tube somewhere. The damper tube pins have the highest voltage spikes and DC voltages anywhere in the set except maybe the HV rectifier. You may even see that it's a different color material than the other tubes sockets in that set. Its filament current is probably highest also.
        Don't forget to replace that super high value resistor from +DC to the AGC line. Now  I see it is 9.1 or 9.6 Meg Ohm in the Magnavox 36 chassis I'm looking at. If that resistor is open (an old carbon resistor that high in value will open quickly if it has DC voltage on it) it will shut off the tuner and video IF tubes. You will get a blank raster and no sound at all.
      The tube that is the audio output tube in the chassis is still used even in the ST but not for audio circuits. It is used simply as a voltage dropping resistor to lower the +DC to about half its value--from 280 VDC to 150 VDC. If it goes bad somewhere, the +150 VDC goes away, and your tuner tubes, video IF tubes and sound IF tubes lose their DC plate voltages. So check the cathode of the audio output tube (it may be labelled voltage divide tube on your chassis) for +150 VDC.
         I hope the schematic I'm looking at is similar to your set. Is your schematic somewhere in the downloads section?
              Good luck !!
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Bill on September 19, 2019, 08:24:18 PM
I'm glad to hear it was something simple, to get your PT to light again. :)  Now onto the next hurdle, which I'm sure you will figure out in no time flat.  All of your friends here on the forum are thinking good thought for you.

Bill

Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 19, 2019, 09:24:22 PM
There is a copy of Sams 591 here on Downloads.  I also have the Magnavox version, essentially the same with a couple notations "Some Theater models...." included. 

I believe the high value resistor you mentioned, from DC to the AGC line, is R43 on the schematic.  For some reason finding it on the drawing escapes me at the moment.  I have R43 in my notes as 9.1 megohms in value.  I have it listed as measuring 1.46 megohms.  This, of course, is out of tolerance.  I also have R104, a 1.2 megohms resistor listed as measuring 572K ohms, a difference of -57.2 percent.  These are the only two resistors out of four pages of resistors that check more then +/- 10% of value. 

You may have been out of commission last winter when I went thru this chassis.  I redid all the caps and measured all the resistors on the card table in my den in AZ.  I had forgotten about these two resistors.  I even made myself a note, in large letters, to keep these resistors in mind should I have an issue with the TV.  I see the note here, now.  Old age ain't for sissies.......... ;) :)

I found R43.  That may be the AGC resistor you mentioned.  I see it goes to the video IF strip.  I need to re-measure R43.  The schematic shows it as a 5% resistor.  I've had a little recent experience with drifted AVC resistors.  Do you feel replacing this resistor will make a difference?  R104 is in the grid circuit of the 6GC5 voltage divider.  The output of the voltage divider, at the cathode, goes to the IF strip at 120 volts. 

Another issue I'm having is the fine tuning control on the TV tuner.  It is made to set and forget.  The TV is alleged to have a circuit that controls fine tuning from channel to channel.  You really need to remove the channel knob to fiddle with the fine tuning.  It may be all out of whack from me messing with the channel knob awhile back.

Jeez...... ::) :) :)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 20, 2019, 12:01:08 PM
I wonder if I may have two problems.  It seems with this TV I can't just have one problem at a time.  First I have no audio.  I can't induce noise and get it thru the speaker.  Then I believe the tuner is kaput.  I can get a flash in the CRT when I change channels.  That should eliminate the video IF's of suspicion.  I need to dink with the fine tuning some more.  No adjustment of the fine tuning up to this point has changed much of anything. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on September 20, 2019, 01:20:33 PM
                 If you actually have + 120 VDC at the 6GC5 power tube cathode, the 1.2 Meg resistor in the voltage divider at the grid of the 6GC5 is probably OK. The low measured value you get is due to the other voltage divider resister (1 Meg on my schematic) being more or less in parallel with the 1.2 Meg. The +280 VDC power supply probably measures less than 100 kOhms to ground so the high value 1 Meg and 1.2 Meg resistors are virtually in parallel as far as your ohmmeter can tell. 1 Meg in parallel with 1.2 meg is about 550 kOhms, which agrees with your measurement. I'm assuming you measured these resistors in circuit.               
        If your TV tuner is a "turret" style tuner with channel strips on a rotating drum, the oscillator circuit is probably broken and reconnected every time you rotate the channel selector, since coils are switched completely out of the circuit between channels. So your flickers in the CRT as you change channels might be voltage spikes leaking through the power supply. Your video IF tubes could still be biased off from AGC voltages being wrong.
       
        If that high value  9.1 Meg resistor is completely open you would still get a reading on your ohmmeter, about 1.25 Meg, according to resistors I see in parallel with it. I see an 820 k, a 330 k and a 56 k which adds up to 1.2 Meg. That's close to what you got, and the 9.1 Meg resistor could still be open.  On the schematic I have, the 9.1 meg resistor is in the circuit area as the first video IF tube. It should be right near the AGC wire from the VHF tuner. If its really inaccessible, you can just connect one lead of your DMM to the AGC wire on the VHF tuner and the other lead to the 280 VDC anywhere on the TV chassis. (make sure it's set on DC volts !!!)
         I remember that the same resistor that had opened up on the Zenith B&W TV I looked at years ago caused a blank white raster and no sound
(no snow and no rushing noise). You don't even have to unsolder the resistor to check it. All you have to do is place your DMM leads across it when the set is powered up. The DMM is 10 Megohms (most of them are) on DC volts so your DMM would be substituting for the open resistor and you would at least get snow on the CRT and a rushing sound on the audio.
          For some reason or other, every 680 k or higher ohms carbon resistor I've ever seen with a high DC voltage on it has, over years, always opened entirely or gotten way out of tolerance on the high side. It can't be heat related because there's almost no power being dissipated by such a high resistance, even with 280 volts DC on it, so it's well within the 1/2 watt rating. 
         Good luck !!
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on September 20, 2019, 01:35:00 PM
              Oops, I cut and pasted wrong--the  third and fourth paragraphs got swapped. I guess the schematic I'm looking is close enough to the Sams 591 Photofact.   
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 20, 2019, 11:53:13 PM
I don't have the exact schematic for this TV, but , so far at least, I've been able to muddle thru. 


My plan of attack is to first replace that 9.1 meg resistor.  Then I want to check element voltages on both IF strips.  Then I want to check the IF transformers for continuity.  I have tested the audio setup in the stereo tuner part and that seems okay.  I'm just not getting audio out of the TV, period.  Another possibility I'd like to explore is that the fine tuning may be so out of whack, it has killed both audio and video.  I want to avoid removing the TV tuner.  You have to disassemble half the cabinet to get it out.  I want to systematically eliminate all other possibilities first. 


My stepdad was a TV repairman for several years.  He hated working on TV.  He always told me that a black and white TV was an AM-FM picture radio with sync, sweep, high voltage sections added to control a monochrome cathode-ray display.  The tuner in a TV sends two IF signals into the video IF strip.  The video IF at 45[size=78%]75 mhz, and the audio IF at 41.25 mhz.  The video If transformers and amplifiers process the video IF signal while passing[/size][/size][size=78%], and somewhat amplifying the audio IF signal.  Between the video detector and the video amplifier, the sound signal is passed to the audio IF stage, followed by detection in the audio detector stage.  The audio is then sent to the audio amplifier, in this case the 93 series stereo amplifier.  The video signal is sent to the video amplifier and then on to the picture tube.  [/size]
[/size]
[/size][size=78%]My thinking is, after I am certain that everything is right in both the video and audio sections was to inject a signal at audio IF into the video IF strip to see if I could hear the modulated signal in the stereo speakers.  The video IF can also stop the audio.  I can also send a video IF signal thru the video If strip, but I'm not 100& sure what display I should see on the screen.  These two tests should positively provide evidence to either condemn or eliminate as a suspect the TV tuner.  Of course, if the trouble is placed squarely at the feet of the tuner, we'll remove and troubleshoot it as we see fit.  [/size]
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: 19and41 on September 21, 2019, 02:56:34 PM
If the set has an automatic correction for the tuning, you may have to disable it to do the setting before forgetting. (like disconnecting the vacuum line on the distributor before setting the timing).
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 21, 2019, 10:59:10 PM
The schematic does not make any reference to automatic fine tuning.  Magnavox advertising does.  That is something I'm currently trying to find more information on.  You are right, though.  If it has something like that, I have to take it into consideration in my troubleshooting procedures.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on September 22, 2019, 12:26:36 AM
              I think your TV tuner has a mechanical arrangement to avoid continuously having to readjust the fine tuning each time you change to a different channel.
             It isn't anything like later color TVs that had "AFT" buttons that would connect electronic circuits like AFC on an FM tuner. Those later TVs had an FM discriminator in the Video IF (not the sound IF) and would develop  a positive or negative DC voltage if the fine tuning was misadjusted (or drifted) above or below the correct setting. This DC voltage would feed back to a varactor diode in the TV tuner and bring the local oscillator tube back to the correct frequency.
            This Magnavox had 12 little gears arranged in a circle around a drum or on a disc that rotated with the selector knob. That's why nothing on the schematic shows it. The gears were in place of a screw head on screws that screwed into or out of the oscillator coil if it was a turret tuner, or the gears rotated eccentric cams that moved a fine tuning capacitor different amounts depending on which channel was selected and where that particular wheel was set to. RCA sets had a tiny push button that engaged the gear when pushed and held in, and turned the gear when the button was rotated while held in. The Magnavox had a gear with a slight dead zone and the gear was disengaged for the first bit of rotation. You would feel play in the knob while the gears were being engaged and this is mentioned in the TV instructions as a normal feel.
           They usually call this geared arrangement "one-set" fine tuning, "set and forget" fine tuning or "preset" fine tuning, but never AFT since it isn't automatic in any sense of the word. If you misadjust it, it won't correct itself. But it will only misadjust the channel the tuner was set to when you twiddled the knob. The other channels stay set correctly.
          I don't think any adjustments on the fine tuning will have any effect on a blank white snow-free raster until you first get snow on the video, and that you should get with nothing going to the antenna terminals--in other words no test signal.
             Greg, do you have a digital TV converter box they were handing out 10  years ago while the digital signals were starting out ? The kind that would put an RF analog signal on channel 3 or 4 of a TV like your Magnavox ? Or do you have an old fashioned signal generator that can be set to 40 or 50 Megahertz with internal 400 Hz Amplitude modulation?  That signal should put some large black bars on the TV screen and you can connect it direct to the TV antenna terminals and set the generator to 43 or so Mega-Hertz and put the selector knob on channel 2. Even if the VHF tuner is not functioning, enough 43 MHz should bulldoze through the channel 2 tuned circuits to put some black bars on the CRT. I remember you once mentioned having an old style signal generator with AM option, but I forget if it would go that high in frequency up to 50 Mega-Hertz or so.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 22, 2019, 10:49:58 AM
I have a 12" Admiral Playmate that I've been "testing" on.  The little Admiral, circa 1963, has a nice sharp picture.  I connected the VCR to the Admiral and started fiddling with the fine tuning control.  I could turn the fine tuning far enough to completely lose the audio and I had video on Channel 2 instead of Channel 3 the TV tuner was set to.  I never got a white screen.  It always had snow and a raster. 


I do not have an analog/digital converter box here.  I have one in AZ.  My plan is to use this TV in AZ in my den so I can watch MeTV over the air.  There are over 70 OTA stations available in the Phoenix area.  We are in a fringe area here.  Nobody uses OTA TV unless they are really cheap and like to watch two or three channels only. 


I don't have any kind of generator that will work with TV.  That is my goal for this winter.  I'm hunting for a B&K Analyst, either a 1076 or a 1077.  This instrument should have all the signals I need to troubleshoot this TV chassis.  I don't want a room full of lab-grade TV test equipment.  I'll need to get my scope running and get the correct probes, then go to Scope 101 to learn to use it.


I may have mis-spoke about the "automatic" fine tuning.  The Magnavox tuner is spring-loaded where you have to push the fine tuning knob down to make it work.  It is obnoxiously sized and is inconvenient to use, particularly if you have big fingers or long finger nails.  So one would set the fine tuning, then not to have to fiddle with it again.  Mine has been turned and turned, so it can't be close to where it needs to be.  Magnavox advertised this gimmick as a whiz-bang modern feature.  Now that we have determined that there is no electronics involved, the mystery is solved.


We have our old RCA Home Theater vintage 1992 working here on a cable box.  When we signed up for fiber optics TV we were told that as long as we kept this certain box, we would have a full screen picture on an old CRT set.  Now we don't, we have that stupid black stripe at the bottom and at the top of the picture.  So now I need some kind of doodad to make the picture full again.  I'm told a VCR might do it, I'm told I need an RF modulator.  I have a spare VCR, maybe several.  How would a VCR work with a cable box to fill the screen on the old RCA?  The cable TV company says we need a new TV.  That's not the point....... ::) ;)


And thank you for the input on what a video IF signal would look like on the TV screen.  The audio IF, modulated at 400 cycles, should just be a tone like you get in a radio, right?  The video IF would be bars.  Got it!      :) :)


Sams lists the audio IF as 41.25 megahertz, and the video IF at 45.75 megahertz.  I'm not clear, yet, on how they get two IF signals to run together, but that's part of being a TV "noob".  Certain facts are above my pay grade at this point.   :-[


I have an old Superior signal generator that is from a time before TV was invented.  It won't even work with FM, so I need to find something appropriate for TV.


The tuner in this TV has a little plastic gear on a shaft into the tuner.  The fine tuning knob is spring loaded.  You have to push down on the fine tuning knob to engage that little plastic gear.  My thinking is the fine tuning knob is made to be obnoxious to use for a reason.  I am considering removing the channel selector knob in order to adjust the fine tuning.  That would open up its own can of worms, however.  Knowing me, I'd bust the channel knob.   ;)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 23, 2019, 11:39:13 AM
I am in the market for TV test equipment.  B&K 1076 or 1077B TV Analyzer, Sencore VG-91 generator, three each 7-pin test sockets, a 9-pin test socket and an octal test socket.  I'll need a high voltage probe down the line a bit, but if I can find one reasonable and worth the money, that would be great.  I don't need both generators, but one or the other would help.  I'll need some probes for my old Heathkit scope, but I don;t know the model number right off hand.  It worked the last time I tried it, so I believe it will be okay.  I'd like leads and manuals with the generators.  If anybody has some of this stuff, I'd appreciate it.  I'd like to avoid ebay if I could.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: ed from Baltimore on September 23, 2019, 12:22:13 PM
             Just curious Greg--what model number is your Superior signal generator ? And your Heath scope and VTVM
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: Harbourmaster on September 24, 2019, 02:36:47 PM
OH Greg!!!   Isn't this the Tester you have been looking for?  https://antiqueradios.com/forums/viewtopic.php?f=15&t=365226 (https://antiqueradios.com/forums/viewtopic.php?f=15&t=365226)
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 24, 2019, 04:36:22 PM
Yep, it sure is and it has manual and leads.  I'll see if I can contact the seller.  Thanks, Ken! 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 24, 2019, 05:40:14 PM
The system wouldn't let me add to my previous post.  All that typing for nothing.   ::)


I have an old Tektronics model 532 scope that was my stepdad's.  Lloyd used to keep it running, but he passed in 2012 and I haven;t turned it on since.  There is a 6AL5 hanging upside down that has a wonky tube socket.  I'm not gonna stick my hand in where there is like ten million volts to nurse that tube like good old Lloyd would.  Lloyd and my stepdad both worked for Honeywell in Phoenix at the same time, but never met as far as I know.  Ironically, they shared a birthday, August 25.  I have a little Heathkit IO-12 that is probably more practical to use.  I bought it at an auction a few years ago for practically nothing.  That is what it's worth, since it does not have any probes.  Condition-wise, it looks brand new. 


I am VTVM poor.  I have nine.  I never pass the opportunity to buy a VTVM.  I have five on my bench, all hot at the same time.  An RCA Senior Voltohmyst WV-98C on DC+.  An unknown model RCA Voltohmyst on DC-.  A Heathkit IM-5228 on AC.  An NRI model W on ohms.  I have a military model URM-250 I use if I need a second one for some reason, like setting the balance on a Magnavox amplifier.  I have a battery-powered Triplett 631 that is a pain due to the battery being expensive.  I have a military RF VTVM that I seldom use.  I have a Heathkit model V-6 with a cracked meter lens and no leads.  And a Knight in similar condition.  I should stock up on Amphenol (?) fittings and flexible wire and get those going if I can.  I also have a Heatkit IG-102 signal generator that I found in my junk pile the other day.  It doesn't look too bad, but, of course, it has no leads.  I have no idea where I got it, or how long I've had it.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 26, 2019, 10:43:04 AM
Shipping on an Analyzer will be more than the Analyzer costs.  I need to try to find something "local" so I can avoid paying so much shipping.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: 19and41 on September 26, 2019, 02:12:06 PM
How's Craigslist looking in your area?
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 26, 2019, 05:25:26 PM
In this area, it does not look very good.  I have more hope for the desert southwest.  Maybe I can find something out there.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: 19and41 on September 26, 2019, 05:38:37 PM
Just for fun, try searching using test equipment.   Sometimes you get a better  result generically.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on September 27, 2019, 10:16:48 AM
I live in an electronics wasteland.  The only time I see any electronics equipment is the occasional auction find.  It typically sells for pennies on the dollar.  I have bought tube testers for $1.  I bought a pickup truck load of radios at a four-ring auction in 2007 for $17.  The closest shop that I'm aware of that works on electronics is almost 200 miles away.  Auctioneers typically can't get a bid around here on sewing machines, CRT televisions, any electronic equipment, record players, console stereos.  Mixmasters are a few dollars, complete with bowls.  Fans can be cheap, or they can start a bidding war.  Not much tube equipment left around here.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on October 23, 2019, 06:17:47 PM
There is an Analyzer on Craigslist here locally.  The seller has had this and other test equipment on Craigslist for nearly a year.  He is probably close to 100 miles NW of me.  He is not being terribly cooperative with getting together and doing business.  So........I reckon the search is on for someone who wants to sell one and knows something about what he has.  Like does it work, is it complete, does it have manuals and leads.  I don't want to make a 200 mile round trip with no commitment for a deal of even for the guy to be home when I get there.  If anybody knows of anything, I'd appreciate the heads' up.


There is a link earlier in this thread of a member of ARF who has one of these for sale.  I'll reach out and see if he still has it.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: 19and41 on October 23, 2019, 10:17:38 PM
I was looking on Ebay.  Sencore made decent test equipment and made it until relatively recently.  They have an analyzer model VA48 that looks like it might be a possibility.  The rub is the freight on them.  If you keep looking you might find a medium between cost and shipping.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on October 23, 2019, 10:35:25 PM
I've kinda got my hat set for a B&K older tube model tester to use with old TV's.  More to play with than anything else.  Freight is going to be the killer with anything you buy.  Unfortunately, sometimes things are not local.  I'll have to see what I can find, then figure out if the total cost makes sense. 
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: 19and41 on October 24, 2019, 06:42:26 AM
When I have a need for such an item, I bookmark a search on Ebay.  If a auction looks good, try Gixen.  You can post a snipe with or without first bidding on an item.  It's basic service is free, they encourage the next step up which is $6 a year.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on October 24, 2019, 01:58:16 PM
I found a nice model 1076 analyzer on another forum for $65, plus $85 shipping to me.  $150 for this equipment is not cost effective.  The search goes on.  I need to find some test sockets as well.  Seven pin miniature, nine pin miniature and octal.
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: electra225 on October 24, 2019, 02:54:00 PM
Test sockets are expensive!  I figured I could find a set for $10 or so.  Not..... >:(
Title: Re: Magnavox Stereo Theater 1MR418M restoration
Post by: 19and41 on October 24, 2019, 04:03:26 PM
Been there done that!  ;D