Author Topic: Magnavox Stereo Theater 1MR418M restoration  (Read 24215 times)

ed from Baltimore

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #405 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.

electra225

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #406 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.



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ed from Baltimore

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #407 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 ??

ed from Baltimore

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #408 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.

electra225

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #409 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.
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ed from Baltimore

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #410 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.   

electra225

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #411 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.
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firedome

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #412 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!
Happy Motoring! from Roger in NY

electra225

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #413 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.
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electra225

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #414 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.   :) :) :) :)
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Bill

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #415 on: May 14, 2019, 05:30:04 PM »
Good work Greg!   I always feels good when progress is being made.   :)

Bill

electra225

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #416 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. 
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Motorola Minion

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #417 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.
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Dave

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #418 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.
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electra225

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #419 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. 
I don't need Google.  My wife says she knows everything.