Author Topic: Magnavox Stereo Theater 1MR418M restoration  (Read 4882 times)

electra225

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #240 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. 
I'm great at multi-tasking.  I can listen, ignore, and forget all at the same time.

SeniorSteve

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #241 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.

electra225

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #242 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.
I'm great at multi-tasking.  I can listen, ignore, and forget all at the same time.

electra225

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #243 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.
I'm great at multi-tasking.  I can listen, ignore, and forget all at the same time.

electra225

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #244 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.
I'm great at multi-tasking.  I can listen, ignore, and forget all at the same time.

Alfista

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #245 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

electra225

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #246 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.
I'm great at multi-tasking.  I can listen, ignore, and forget all at the same time.

Bill

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #247 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

electra225

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #248 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.
I'm great at multi-tasking.  I can listen, ignore, and forget all at the same time.

ed from Baltimore

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #249 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 !!
         

electra225

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #250 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.
I'm great at multi-tasking.  I can listen, ignore, and forget all at the same time.

Larry H

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #251 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...
--Larry

electra225

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #252 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. 
I'm great at multi-tasking.  I can listen, ignore, and forget all at the same time.

Larry H

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #253 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.

--Larry

electra225

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #254 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?
I'm great at multi-tasking.  I can listen, ignore, and forget all at the same time.