August 1977 RCA Colortrak - Videokarma.org TV - Video

pac.attack76 · #1 08-09-2026, 02:41 PM

Looks like someone wrote on the back, CTC90D. Anyway, just got this from a guy that was a tv tech who had kept up maintenance for years. It doesn't have any color to it and it has a bit of convergence issue near top. Just looking where to begin. Want to use this set with matching vcr, ced unit and atari.

pac.attack76 · #2 08-11-2026, 09:38 AM

I've been looking at this for a bit. Due to the move from where I picked it up, an hour away, the yoke had slid back and shifted also causing the purity rings to get pushed back to the socket. I've put everything back up where it should be but I still have nearly no color and convergence is a little off.

vol.2 · #3 08-11-2026, 10:01 AM

Quote:

Originally Posted by pac.attack76

I've been looking at this for a bit. Due to the move from where I picked it up, an hour away, the yoke had slid back and shifted also causing the purity rings to get pushed back to the socket. I've put everything back up where it should be but I still have nearly no color and convergence is a little off.

Maybe there's an issue with the color control? I would pull it and check resistance across the pot and make sure it's not flaky.

pac.attack76 · #4 08-11-2026, 10:04 AM

Quote:

Originally Posted by vol.2

Maybe there's an issue with the color control? I would pull it and check resistance across the pot and make sure it's not flaky.

The dial at the front behind the door?

vol.2 · #5 08-11-2026, 12:11 PM

Quote:

Originally Posted by pac.attack76

The dial at the front behind the door?

I'm not familiar with you're specific set, but there should be a color control on it. When you turn the color down all the way, it should make the image black and white. It essentially is there to let you adjust the chroma subcarrier level.

If there was something wrong with the control, like there was a break in the carbon track, or it was just really dirty, or there was a bad solder joint or something, that could cause a loss of color like you are seeing.

Another thing that could cause loss of color is if the the tuning is off and you are using RF. Sometimes if the tuning capacitors are dirty, that can cause weird effects like loss of color. That generally just requires spraying the tuner and moving it back and forth a bunch. This would only be an issue if you're using RF input, not if you're using composite.

There's plenty of other possible issue though. It could be a bad component in the chroma demodulation section or a bad power supply source voltage for one of those areas. I'm just giving you low hanging fruit to test

pac.attack76 · #6 08-11-2026, 06:35 PM

Quote:

Originally Posted by vol.2

I'm not familiar with you're specific set, but there should be a color control on it. When you turn the color down all the way, it should make the image black and white. It essentially is there to let you adjust the chroma subcarrier level.

If there was something wrong with the control, like there was a break in the carbon track, or it was just really dirty, or there was a bad solder joint or something, that could cause a loss of color like you are seeing.

Another thing that could cause loss of color is if the the tuning is off and you are using RF. Sometimes if the tuning capacitors are dirty, that can cause weird effects like loss of color. That generally just requires spraying the tuner and moving it back and forth a bunch. This would only be an issue if you're using RF input, not if you're using composite.

There's plenty of other possible issue though. It could be a bad component in the chroma demodulation section or a bad power supply source voltage for one of those areas. I'm just giving you low hanging fruit to test

Ill check into it. I really don't know at this point. I dont even see tuning. There's only a coax and 2 sets of screws.

vol.2 · #7 08-11-2026, 09:53 PM

Open up the door at the bottom of that panel and take a picture of the color control. Make the picture larger. Your other pics are too small.

pac.attack76 · #8 08-12-2026, 07:27 AM

Quote:

Originally Posted by vol.2

Open up the door at the bottom of that panel and take a picture of the color control. Make the picture larger. Your other pics are too small.

vol.2 · #9 08-12-2026, 09:43 AM

That's it. What happens to the image when you swing that color pot from end to end? Nothing at all?

The color pot is the one on the top right just to be clear.

pac.attack76 · #10 08-12-2026, 07:24 PM

Quote:

Originally Posted by vol.2

That's it. What happens to the image when you swing that color pot from end to end? Nothing at all?

The color pot is the one on the top right just to be clear.

Yeah no change at all.

vol.2 · #11 08-13-2026, 12:44 PM

Quote:

Originally Posted by pac.attack76

Yeah no change at all.

In that case, I would remove the control from the circuit and test it for continuity with a DMM.

If you can rule out that the control as a problem, then you can focus on other things.

Assuming the control is okay, then my next step would be to check from the chroma signal out of the demodulation area. I personally wouldn't attempt it without a schematic though

There are other guys on this forum who might be able to point you at some part to check after that or not, but it's going to get increasingly more complex as you rule out low hanging fruit like a bad control

vol.2 · #12 08-15-2026, 11:54 AM

It would probably take an afternoon to test every component on the board and reflow all of the solder.

Of course, the IC on the on board could also be at fault, which would be harder and possibly more expensive to replace, but it's worth spending a day and making one perfect board to test with first

Without the schematics, I wouldn't know which pins on that IC to probe for a chroma waveform, but possibly one of the other guys here with more 70s TV experience remembers what IC it is and what it's doing

But first things first; lots of these issues can be just bad solder joints and/or toasted passives

pac.attack76 · #13 08-15-2026, 09:59 PM

Ill try pulling that board and see what's on the other side. Doubt I'd ever find a replacement. Better if I can fix one of these since there's 2 of them.

pac.attack76 · #14 08-15-2026, 10:35 PM

Ok, weird. Pulled board out and figured I'd put the old one in to see what happens. Had to set color and tint but here's what I got. Should I look at anything else before I close it up?

vol.2 · #15 08-17-2026, 11:03 AM

Quote:

Originally Posted by pac.attack76

Ok, weird. Pulled board out and figured I'd put the old one in to see what happens. Had to set color and tint but here's what I got. Should I look at anything else before I close it up?

If it we me, I would pull and test every component on that little board, and replace anything that is out of spec (usually 20% for most components, maybe 10% for important resistors). The main concern I would have there is that the color board has an IC on it that could get stressed if some of the components have drifted too much, and that could be hard to find a replacement for it if it dies. 1970s ICs do not have a reputation for robust lifespan.

Also, your convergence is atrocious, so I would definitely dial that in with the yoke first. Caveat that yoke carries lethal voltages, so proceed at your own risk. Do whatever you have to do to learn how to handle it before you do anything.