Colortrak CTC120

[Kamakiri]

The coil pictured is the one with the light purple center, with the screwdriver stuck in the center (didn't know the pic would turn out this good ).

No markings on it that I could see.

[Findm-Keepm]

Originally Posted by davet753

PM me if you need the coil, I think I have one in my tube caddy. They were a cheap, commonly used part back in the day.

I don't think we ever replaced a single one - the RCA Service seminar techs gave us a heads up on the "rock the quad coil" issue. We had the square ended dittle stick in a little ziplock bag hanging on the wall by the bench for use. I carried it with me to Alabama one time to fix my dying great aunt's tv, not for her, but her caretaker. The RCA Goldenrod even warned of mistakenly replacing the coil, when all it needed was adjustment. Apparently (this is going on an RCA "Communicator" article) RCA didn't age the sets in the design phase, and aging of components would pull the audio quadrature out of phase, necessitating the adjustments.

When we stripped a chassis, we always pulled the cores, so if the core is the only issue, PM me and I'll see what I have.

EDIT: I have two - not sure which one you need, both are yours if you need them, Free.

[Kamakiri]

Problem is that I can't get the sucker to budge!

Granted, out of all the tools I have, I don't have that little square thing, so I tried to turn it with a similarly sized screwdriver which *should*, I assume, turn the sucker. Nothing.

I did change out all the filter caps (the main one plus the ones on the board) as well as the .1's, and I have to say that the picture is MUCH sharper and brighter than it was. Also had a bad drifting issue with the tuning, and that's gone. This set's a keeper for sure. The colors are lush and vibrant, just like a color set should be

Now with the recap, it doesn't make any difference if the screwdriver is there or not. Of course I might have managed to budge that coil and not know it, who knows. I might just need those slugs, but I either need one of those square screwdrivers, or need to figure out how to move the one that's in there now. Where do you buy them?

Now if I can get this low sound thing fixed, I'll be good!

[Jon A.]

Nice set for sure, I'd grab one given the opportunity.

[AdamAnt316]

Very cool! I grew up with a set like that (albeit in a more plain cabinet, with a swivel on the bottom IIRC) in our living room. Unfortunately, in the early-mid '90s, I tried to adjust something about the picture using the little control panel in the back, and royally messed things up. Eventually, it went away, replaced by a plastic RCA 27" set which wasn't built nearly as well (waves of static appeared on the screen every time it was turned on). I still have that control panel as a reminder........
-Adam

[drussell]

I still have my CTC-120... It is the first TV I ever bought, in 1993 or 94, when I was a teenager. My parents had bought a new 27" Sony for the living room when we moved into the new house and the now "spare" old Admiral 19" color that I used in the basement died. The repair shop wanted some ridiculous amount to attempt to fix it, so if I wanted a TV down there I would have to buy my own. I should have tried to fix that Admiral myself, though, I probably could have fixed it, even then.

I found the RCA in the Bargain Finder. I think I paid $220 for it. The seller said they had two similar 25" RCA models (seller was claiming 28") and said I could have either one. One was my cabinet (model GJR641) and one in what I believe is the same cabinet Kamakiri has, I've seen that cabinet before. The day we took the van over to pick it up the seller had taken one of them to storage but I figured I wanted the one I have anyway (it looked a bit more modern) although they did say they thought the other one had a "clock" on it. I later learned this was the optional "OSD" module which had perhaps a clock and maybe showed the channel numbers on-screen? I can't seem to spot the info in the SAMS right now other than the picture of the "MSD001" OSD board but I thought somewhere in there it said what it did, I'll have to look more closely.

I haven't used it for years but it's in my living room...
I really should get it back up and running, been sitting there far too long! It was working until.....

I started adjusting it one day as I tend to do every 5-10 years on my daily-use type sets just to touch things up and had the brainwave to actually get a service manual for the ol' girl since now that everything is on the internet, it would probably lead me right to one. I ended up buying the SAMS for it, printed it out on 11x17" paper and set to work reading up on adjusting everything I could since I finally actually had a SM. Makes sense, right?

I started reading along and was looking at what all I could adjust, and another brainwave, "Hey, Wait! I have a 'scope! I can do most of this stuff properly!" Even though I didn't yet have equipment to sweep and whatnot, I figured I could at least do most of the adjustments where you check and adjust levels and such based just on waveforms, so I pulled out my scope, set it on top of the TV and dove right in, checking and adjusting.

Then, disaster struck... I had stupidly clipped an aligator clip lead onto the probe I was using on the oscilliscope, precariously running up and across to the scope while I was probing something like the video signal levels around the video processor IC. The aligator clip slipped off the probe tip and fell into the horizontal output area. (GASP!! EGADS!!) I still had color bars at that point yet, even more stupidly, instead of quickly pulling the power and retrieving the lead, I grabbed at it and it fell down farther into something high voltage... POP! I looked up at the mirror in front of the set and instead of color bars, I had black screen with a faint raster... ARGH!

Horrified, I started looking at the schematic to see what I'd killed based on where I was probing and realized it would be U701, an RCA 153685. "Oh great," I'm thinking, "I'm never going to be able to find some proprietary RCA 153685 chip for a 20 year old TV." Bewildered, I started reading through the SAMS and when I get to the semiconductor table, lo and behold, SAMS to the rescue. The chip crosses to a standard ECG/NTE number! NTE844! Perhaps there is hope after all...

I called up the local electronics place I use that stocks NTE and, thinking they've probably been long discontinued, sheepishly ask if they happen to still have an NTE844. Not in stock, but they can still order one... Hooray!

I got it a couple of weeks later but since I'd been looking at the schematic and I'd pulled the datasheets for various manufacturers versions of the NTE844, I realized that I could probably bodge an S-Video input on there right at that chip (it is the chroma/luma processor) so I started building a little extension board with a socket for the NTE844 and room for some switching circuitry to add the video input. Procrastination and other, more pressing projects set in and there it still sits... The NTE844 still in it's bag atop the TV. The little board I started building is sitting atop the TV. The SAMS is sitting right there. I'm ashamed to admit it but it's probably been sitting there for almost 10 years now...

I started trying to make a video about it a couple of years ago when I first found Bob Andersen's YouTube channel and got the bug to work on some older stuff again but I didn't have a video camera good enough to get any kind of quality. I should try the little Cannon digital camera I have here now. It's video abilities might be good enough for a start, since I really would like to post some YouTube videos of some of the stuff I end up working on. I think some people might find them at least somewhat interesting and/or mildly amusing. I certainly love Bob's!

Maybe this CTC-120 thread is the jumpstart I need to actually turn the thing around and finally DO something about it!

The thing has an awesome picture!

[Kamakiri]

Wow, what a story! Sounds like it's time to get your old gal working again!

Does your manual spec the part number of that quad coil that's pictured in post #16 here?

And as long as I'm in there, there is an IC in the audio section that is covered by a copper heat sink. Happen to have a part number on that? If, that is, your manual covers the 120 and not just the A....

[drussell]

I think mine is actually just a plain CTC-120 also, the SAMS just happens to be labelled A, perhaps it just covers some later revisions or something, although it doesn't even list my GJR641 in the 47 models it does list on the front page. Go figure.

The diagram pasted inside my cabinet says CTC-117/118/120

This SAMS covers a whole swack of models. For example, it includes at least 5 different tuner setups, 3 different ones with the LED display on the front, the one that uses the OSD and includes the clock and at least one mechanical tuner.

L201 Quadrature (13.6uH) part #143834

U201 part #153684 crosses to:
ECG: ECG1175
NTE: NTE1175
GE: GE-1175
RCA: SK3212/1175
Workman: WEP2175/1175
Zenith: 221-Z9056

An ex of mine once picked up a similar chassis, portable, mechanical-tuner model at a garage sale for a few dollars because the sound didn't work, thinking at worst we'd be using it directly off of a VCR to get remote capability and had a small stereo with aux input right there anyway. When I pulled the back and twisted the adjustment marked Audio IF or somesuch about 1/8 turn the sound came up perfectly.

That TV worked like a charm for years...

[drussell]

Troubleshooting - Audio:

If there is no sound, check the volume control voltage at pin 1 of Plug P302 while the volume is varied from MINIMUM to MAXIMUM. The voltage should vary from about 0.67v at MINIMUM to 6.17v at MAXIMUM volume. If the voltage is absent troubleshoot the Remote Receiver Board (MCR017A) and the Tuner Control Board (PW2500). If the volume control voltage is good, inject an audio signal at pin 9 of the Audio IC (U201). If there is no sound at the speaker, check the Speaker, Plug P201 and the voltages and components associated with pins 1, 2, 4, 7 and 9 of IC U201. If sound is now present, check the voltages and components associated with pins 10, 11, 12, 14, 15 and 16 of IC U201. Also check the Sound Take-Off Transformer (T301).

U201:
1 - 25.3v
2 - 12.3v
3 - GND
4 - GND
5 - GND
6 - N/C
7 - 2.05v
8 - GND
9 - 8.84v
10 - 4.12v
11 - 4.12v
12 - 6.14v
13 - GND
14 - 4.23v
15 - 4.23v
16 - 6.34v

Let me know if you need the audio chunk of the schematic.

[drussell]

I thought I would post the audio section schematic anyway, in case it helps:

[Edit: Interestingly the forum seems to have converted the uploaded grayscale .GIF to a .JPG]