GE M935AWL restoration

[Yamamaya42]

Video IF looks good from what can be seen through the cataract.

For sound, most tune in the best pic, and them adjust the sound IF coils for best audio.

Most of the time this can be done by ear, but sometimes, it's best to follow the Audio IF steps laid out in the SAMS.

[bandersen]

I also have no color if I tune in for best pic though. I'm right on the edge of losing everything in these screenshots.

[Yamamaya42]

Originally Posted by bandersen

I also have no color if I tune in for best pic though. I'm right on the edge of losing everything in these screenshots.

For that the color AFC setup helps, symptoms of that being off is poor color lock, or rainbow (barber pole effect). symptoms if bad video IF would be bleeding color mostly reds, that is especially seen when you fine tune, this of course goes hand in hand with the chroma bandpass. My guess is that it just needs a touch up on color AFC and sound IF.
unless someone really messed with it

[bandersen]

Tuner tubes are fine. Malloy circuit breaker, new CRT socket, polypropylene caps and a beefy power resistor have been ordered.

I'm hoping it hasn't been messed with. It's the sound being so far off that really surprised me. None at all until the station is almost tuned out. Usually with intercarrier sets you get at least some sound throughout the fine tuning range.

[Yamamaya42]

The sound has always been a bit weird with these with DVD/VHS/LD input vs converter box, you seem to get great sound on one, then get crap when you change to a converter box, then tweak it to work great with a converter box, then the sound sucks on DVD/VHS/LD input, if you have a DVD/VHS/LD input source, you may want to try that to see if the sound acts any better before any adjustments.

[Yamamaya42]

Those mystery white elenco capacitors, (.001) one of them is C70, on the plate of the vertical output, and is having the hell beat out of it, and may be the source of the lack of full sweep, along with C4.

[Zenith26kc20]

Looks a lot like RCA but those compactrons say some General Electric.
Is the color circuit a crystal ringing GE or RCA circuit?

[Yamamaya42]

Originally Posted by Zenith26kc20

Looks a lot like RCA but those compactrons say some General Electric.
Is the color circuit a crystal ringing GE or RCA circuit?

It's a clone of a RCA-CTC 15, with extensive modifications all over the set, even a few hints of Zenith tossed in here and there.
The color circuit looks to be RCA, the horizontal oscillator, seems to be Zenith.

[bandersen]

Curiously, all the tubes are GE except the horizontal output, HV rectifier and shunt regulator being RCA.

New CRT socket, HV polypropylene caps, power resistor etc have arrived.


Still waiting on the NOS circuit breaker to arrive. Hppefully, tomorrow. The current one consistently pops after less than a minute of power.

[Yamamaya42]

Originally Posted by bandersen

Curiously, all the tubes are GE except the horizontal output, HV rectifier and shunt regulator being RCA.

New CRT socket, HV polypropylene caps, power resistor etc have arrived.


Still waiting on the NOS circuit breaker to arrive. Hppefully, tomorrow. The current one consistently pops after less than a minute of power.

I kept the bum socket from mine to use to test tubes later, as I had none with my crt tester, just a universal connector with crappy leads.

[bandersen]

I do have the proper adapter with my CR70. Finally had a chance to use it!

Here's a portion of the color circuit.

Quite surprised to see the sound is picked off after the 3rd IF stage making it a sort of split carrier set. No wonder the sound is off. Should be fairly easy to tweak assume the cores aren't frozen.
Full PDF copy of the SAMS https://drive.google.com/file/d/1-XO...ew?usp=sharing

[old_tv_nut]

Not a split-carrier - note the sound IF detector X8, whose purpose is to produce the 4.5 MHz intercarrier. This allows the 4.5 MHz in the video path to be strongly attenuated, to prevent 900 kHz chroma/sound beat patterns in the picture.

[bandersen]

That's what I meant by sort of. It's not taking the sound after the video detector like other intercarrier sets.

[old_tv_nut]

I still wouldn't call it "sort of" split carrier. "Split carrier" is used too often as the code words to refer to the fine tuning problems that split carrier sets have as opposed to intercarrier.

Maybe "dual detector " or "intercarrier with separate sound detector."

[bandersen]

Semantics aside, this set does have the same problem that split carrier sets have. There is no sound at all until I adjust the fine tuning to the point where the image almost disappears.