Magnavox C-36-20-11 TV chassis troubleshooting

[uncleputz]

I have found that switch is stuck. Or just shorted. I haven't figured out exactly how it works, but I can take it apart then figure it out from there. Channel 3 on the Analyzer actually comes in better on Channel 4 on the TV, so fine tuning is pretty far off. Like I said, I have lots of tinkering yet to do, but i'm taking my time and experimenting and learning as I go.

[uncleputz]

First, let me thank everyone here who helped with this project.

I haven't taken pictures yet, but I will get some and get them posted if there is interest. This TV works really well. After the no sound situation got squared away, I connected a DVD player to make my finally adjustments. I had the fine tuning on channel off. You had to turn to Channel 4 to get Channel 3 to come in. I got that sorted. Originally the CRT checked fairly weak. After running for five or six hours, retesting shows the CRT tests almost like new. Who knows how long it sat unused. This old Maggotbox doesn't perform like a Zenith, but certainly better than I expected. The sound is awesome, although not stereo, since it passes thru the stereo amp and speakers. It could use about a quarter of an inch more vertical height yet. Very clear and sharp picture. It doesn't bloom at higher brightness. Vertical and horizontal are rock solid. I still need to sort the record changer and I want to build a new back for the cabinet. This will not only let the electronics show better, but it will provide better ventilation. Every tube in this stereo are on when the TV is on, even the Multiplex adapter. You think they would have shut off the components not necessary for the TV to work, but nobody worried about pulling 320 watts in a black and white TV back then, I guess. I am thrilled with how this project turned out and I thank you all for all you did.

[Electronic M]

That's great to hear.

One thing you can do on these if you would like stereo sound is identify the TV sound input on the stereo chassis and figure out where the 2 stereo channels get shorted to mono then un short and bring a line level audio stereo input out the back for your VCR/DVD player/HDMI to composite AV adapter/ whatever you are using as a signal source to connect to.

Some machines have a stereo input connector and the shorting to mono is done in the cable from the TV, others have a mono jack and the stereo to mono short is somewhere between the mode switch terminals and the input jack.

I'd be tempted to add a switch on the back that would allow you to select between external stereo audio and internal TV sound.

[old_coot88]

Some piccys please.

[uncleputz]

I tried posting pictures. The software says my pictures are too large. So...

The model number is 1MR418M. It was the top line 400 series of Stereo Theater Magnavox built in 1962 using a 27" 27ZP4 picture tube. It uses the 93-series stereo audio amp, 70-series Multiplex adapter, 79-series AM-FM tuner and a solid state remote control chassis. Magnavox built two other versions of the Stereo Theater, the 300 series with a 24" CRT and the 200 series with a 23" CRT. Magnavox also built a color Stereo Theater, but these are exceedingly rare and I've never seen one in person.

My Stereo Theater was found by a member of our console stereo forum in an abandoned house that was being torn down in Detroit. The house had a hole in the roof. This old stereo was found under a staircase with debris all around it that had protected it somewhat from the elements. He rescued it and put it for sale on the forum. Since it was one of the models on my bucket list, I made arrangements to make it mine.

The cabinet is 60" long, compact for a three-in-one unit of that day. IT had been exposed to so much cigarette smoke, the top of the cabinet was black with nicotine and dirt. Everything inside the cabinet, all the electronics was coated in sticky cigarette residue. There was a mouse nest under the amplifier. The picture tube was ready to fall thru the front of the cabinet. It couldn't fall backwards so the shadow mask and safety glass kept it from falling to the front. But, typical for even neglected old Magnavox stereos, the radio worked, the changer did not, the TV did not. The TV chassis would not even let the tubes light.

I removed all the electronics and wiring from the cabinet, including the CRT. It took me two years to get the electronics cleaned and repaired. A proper schematic or service literature for the entire unit did not exist. I never found anything for the tuner. I got a "close" schematic for the TV chassis, which served me well. The amp I was familiar with and I finally found a schematic for the remote control, although I have never done anything with it and don't plan to. We took the cabinet as far apart as we felt was safe. We cleaned each piece with mineral spirits to get rid of the smoke scum, then sprayed the inside of the cabinet and all its parts with three coats of shellac, followed by three coats of satin polyurethane to seal the cigarette smoke and to keep it from smelling like cigarettes. The outside of the cabinet received 15 coats of gloss polyurethane, sanded from 400 grit to 2000-grit to knock down the gloss a tad. We used gloss material to heighten the grain effect in the cabinet. It turned out nice. Magnavox advertised that they used "10 coats of hand-rubbed oil finish" probably tung or teak oil. We used black grille cloth to give it a "mid century modern" look. It originally had two different kinds of grille cloth, for some odd reason. I got this Stereo Theater in 2017 and just got the TV working. My next task is the changer, but that should be a piece of cake compared to the TV.

I realize this is just a Magnavox, not a Zenith or anything important and worth messing with. I couldn't be happier that I finally got it going and I'm as proud of this thing as I would be of a CT-100 or whatever. I put a lot of myself into this project and it fills a slot in my Magnavox collection between the big Imperial and the Symphony.

[Electronic M]

One thing. The CRT Cabinet Mask, and CRT Shadow Mask are 2 different things. Only color CRTs have a shadow mask and it's inside the CRT between the phosphor and electron gun....It's basically extremely high-precision window screen designed to keep the red gun from hitting green and blue phosphor dots and vice versa for the other guns.

All TVs have a cabinet mask but only color sets have a shadow mask, and if you ever see the shadow mask with the naked eye there's either internal coating missing or your color CRT has been de-constructed in some permanent manner.

IMO average (PP) Magnavox audio consoles beat average (single ended ) Zenith consoles, though high-end PP Zenith's give most Maggie's a run for their money.

I redid the phantom remote on my Maggie roundy, and IIRC I did a YouTube video on it. If you have a scope and a little bit of patience those remote units aren't difficult (the bellows hand units can be a bit of a headache if not functional, so using a tuning fork or electronic remote hand unit from another set may be easier).

[uncleputz]

I told you I was a TV rookie. I meant the plastic thing, shaped like the picture tube face, located between the picture tube and the safety glass. It has a Magnavox emblem on it and a channel indicator for the remote control. I've never owned a Zenith audio console, so can't compare those to Magnavox. I probably won't since I avoid most non-TV things made by Zenith. I respect their TV sets, but their radios are infested with rubber wiring and SMD. And the famous green crud.....