GE M935AWL restoration
 

I was contacted way back in Dec 2023 about some free sets in Winchester Co, New York. A house needed to be cleared out and they weren't sure what to do with these old TVs.

Turns out they had two 60s color roundies and a B&W set. It's my understanding that when they stopped worked, they were just left as pieces of furniture. The original owner passed in the 80s and his wife went to live with a relative. It appears the house was left untouched for decades.

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These are the photos I was sent.
I passed on the B&W but made arrangements for the color sets.
Finally, after 10 months of waiting, they have arrived!
I'll focus on the GE in this thread and start another for the RCA.
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You can see faint outlines where a sculpture and set top box sat for many years.
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Here's a look inside.
21FJP22 work up after a couple minutes and tests like new.
Yoke, degaussing coil and grounding wire were found disconnected.
All the tubes except for horizontal / HV stuff are original GE date late 1964. All test like new.

6JS6, 3A3C and 6EL6 are RCA branded.
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Tried a slow power up and quickly realized the is no B+. Only the filaments are getting power. Likely the circuit breaker is shot.

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Trying to pull the chassis right now.

Also, As you showed in your video, the degaussing coil was unplugged, (plugs into left side of chassis), if this is not plugged in, and the VDR/thermistor combo is bad, it will also kill all power, as it's in line with the breaker, the diode pair seemed rather robust in this set, almost overbuilt, they could go bad, but so far, I have not seen any in the few color sets I have done.

BTW, those chassis clips are a royal pain to get back in there right and tightened down, it's understandable why they were just left in there like that!

These things?
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Looks like there was some trouble with the focus pin. Wire is directly soldered to the CRT pin!
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Decided to pull the chassis so I could give it a good look over.
Crazy clean underneath. No obvious signs of any old repairs.
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Yes, the circuit breaker is open. There's also a split bumblebee right across the AC line.

I suspect the thermistor or VDR are bad as well since the degaussing coil was disconnected. Oh yeah, I can see a detached lead in the photo!
Are compatible parts even made anymore?
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OK I'm really glad I pulled the chassis now. That terminal in the center of the screen was never soldered!

Are these vintage EM type capacitors plastic film?

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yes, those clips hold rear of the chassis.

I have this weird feeling of Déjà vu! :D

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I replaced the entire socket.

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And yes, you can still get them.
https://talonelectronics.com has many that will work, not exact but will work, sold in pairs. and they can be found in other places.

Looks like C146 & C147 Think they are just standard orange drop film, they should be OK, id they did not burn.

I think Chester electronics in Kenosha still stocks thermistor pairs.

He's also gonna have to most likely replace the focus diode, and the boost diode, But I forgot which one you suggested to use. :(

2 in series i believe.

This. https://www.mouser.com/ProductDetail...BIClpyBQ%3D%3D

You probably can make do with one, but on sets where focus range touches or especially if it exceeds 5KV I tend to use a series pair for added safety.

Yeah, i was having brightness and focus stability problems so I pulled the chassis for the umpteenth time and replaced diodes, as well as the matched pair of 1.5 meg resistors R137/138 on the 6BK4, and it helped a lot!

WOW, that circuit breaker seems rather impossible to find at the needed rating for this set.
But the one for the CTC-15 is out there.
https://www.ebay.com/itm/393284894216
It hopefully should work, if you can't find the right one.

I don't have a screen shot (maybe someone does) but I think that GE is like the set MR. Ed won and kept moving it from Wilbur's living room to his stall.

I was able to get the circuit breaker working with some deoxit. I also have a few used but good breakers.

I'm not sure how the rating works for these.
This set pulls about 3 amps, but I see a lot of breakers label "hold 2.1A". What exactly does that mean? Seems like they are undersized?

It is a bit confusing, from what I understand, they are all slow acting, there is the sustained “hold at” rating, and the trip at rating, but it is never clear what the trip rating is, or how long it must be at or over that threshold for it to trip.

I remember dissecting a bad one a long time ago when I was in High School to see how it worked, it has a bimetal contact that's reset by the button, and wrapped around that is a heater wire that has the current running through it.
And, yes, the contacts do burn and fail often.

this is WAY too big, gotta wonder what it's for, but it is the only one i see with both ratings on it, hold and trip.

https://www.ebay.com/itm/30326748117...Bk9SR8D54sq7ZA

I also got one of these to fix the burned focus connector.
https://www.ebay.com/itm/225235664833

Thanks for the links. Just realized I'm being stupid. The breaker is not whole the whole set - it's only for the B+ supply! The filament supply is fused separately. The common 2.1 amp hold type is probably fine.

There is one way to see how much the draw is, including surge, if the breaker is holding, just AC amp measure with peaking across the faulty / removed thermistor, that should give some idea what kind of breaker hold/trip will work.

FOUND ONE!:banana:

but it's with 2 lesser ones.

https://www.ebay.com/itm/315321107869

tip point 3.25 amps.

I have the chassis pulled. Can't power anything without putting it all back together. Sames does list it as a 3.1 amp breaker.

that's the only listing for a LITTELFUSE CIRCUIT BREAKER 8153.25, which Sames lists as a replacement I can find.
So I guess it's hold at 3a or so which seems high to me and trip at 3.25 amps.

Get it while you can! :)

Parts have been ordered. Meanwhile spot checked a bunch of resistors and caps. All are well within spec. Well, except that 0.047 across the AC line. It's very leaky and in the trash.

I measure about 120 ohms cold on the damaged thermistor. That got me thinking a CL-90 might be a good replacement. It can handle 2A and is 120 cold and about 4 ohms hot.

What do you guys think?

It should work. You can always try and see, with the vintage combos sold, they always show the cold rating, but rarely the hot.

Does anyone know the significance of white tipped tubes?
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I have seen that a few times before, not sure why it's done. :O

I've seen red and yellow tipped tubes before too...No clue what it means.

See if they look like original tubes. Manufacturers could mark them to identify them if they were part of a warranty claim. Just a thought.

From a thread at the Antique Radios forum;

"Painted tops" (usually exhaust tips on miniature tubes) did indeed represent "selected tubes."

Tomer relates the entire story in his book, Getting the Most Out of Vacuum Tubes (Gernsback, 1960). The practice was very common among older B&W TV sets. You'll often see tubes with their exhaust tips daubed in what looks like red or white paint. Many circuits "skated the rim" as far as workability went, and without the cream of the tubes plugged into them, they'd give trouble. When the cream of the tubes began to age out, they gave trouble anyhow.

With audio output tubes, I'd agree that they were tested for precise matching if used in the output of Baldwin electronic organ amplifiers. If used for other purposes (tone generator oscillators maybe?) in other parts of the circuit, they may have been tested for other qualities.

Interesting. They are only in the VHF tuner.

Gave the chassis a good look over and found no more problems. Crazy how pristine it is. Really want to minimize replacing parts.
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Here it is after a bit of cleaning. Axial electrolytic and two white ElMenco caps have been replaced. Also replaced the thermistor.
Will resume trying to reform the original caps with a slow power up.
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The right hand side of R204 needs attention it looks like, where the red wire is hooked, Terminal block looks dark, as does the resistor lead, i replaced the entire thing on mine, new Terminal block with a 20w resistor

no where near as bad a mine was! :P
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MUCH better eBay deal:

https://www.ebay.com/itm/125551787795 (NO relation or affiliation, just on my watchlist for spares for my 2 roundies.) I have one socket and jig M-F 28" extension for 70 degree tubes, so probably won't ever need a spare....

BTW, never buy from Moyers on eBay. Better prices when you call them and deal direct. I'd bet their socket would be $5 less over the phone, but you can't avoid their $9 shipping....

QA marks - proof that the tubes are installed after the tuner mounting assembly is installed in the cabinet. Much easier to shine a light and see two white (or yellow if Magnavox) tips than to reach in for a feel. Some Conn organs did the same with an orangish, almost fluorescent paint on the tips of some "voice" tubes and wire ties in the back recesses. The block on the QA final tag was also colored orange for their stamp.

(blessed to have had a PTS location about 1 mile from Dad's shop.....learned a ton from their youngest tech - I thought it was a PTS thing that many of their test RF amp and mixer tubes had painted tips, but they educated me on the QA thing.)

Just for assurances, we always changed the cap that couples the drive from the horizontal oscillator plate to the HOT grid. Saves tubes, prevents callbacks, and extends flyback life. Any good brand polypropylene cap of same value voltage will do. This goes for any RCA or RCA clone set like yours.

A last thought on breakers. We used mallorys. Had a complete
line of single & doubles. There was also a sub book. I bet
its out there.

Zeno:smoke:

Looks OK to me and measures dead on.

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So did mine, but it's a high stress point, due to the heat and oxidation, it will fail sooner or later, not quite as bad as the bleeder nets in the old RCA BW types, but you may want to deal with it now while you have the chassis out, then having to do it again a year or so later, cause due to the heat involved, it will go at some time in the future.

And a new terminal block which I'm sure you have on hand, + this, https://www.mouser.com/ProductDetail...52Bhysvw%3D%3D is worth the investment to having to put it apart later if you can avoid it, :)

Consider it preventive maintenance, all color sets seem to have a 18+ watt resistor in them in the voltage divider, winch always seems to roast the resistor and the tie points, I always make it a point to replace these with slightly higher wattage ones and new terminal blocks when I re-cap, even if they check OK, cause I don't want to be bitten by it later.

But the choice is ultimately your of course. :)
Going over my old pics, before I replaced the old one, it blew out my IR camera at over 400F, which is what prompted me to put in the 20w, which ran quite cooler.