This 25" RCA CTC121 (model FJR2010T) colortrak 2000 TV was given to me by Audubon5425 after it lost video. Someone scratched off the date; but, I think it's from around '83-'84. It has OSD with clock, bass and treble controls, and audio output jacks (no input jacks). When I fired it up, I noticed the luma portion of the picture was missing. With the color control turned up, the chroma portion of the video could be seen. With the color control all the way down, there is no video. Then, a normal picture flashed on for a second and then it went back out. A few minutes later, the same thing happened. I pulled the back and used the butt-end of a screwdriver to beat around on the chassis. At one point, I was able to restore the picture for about a minute. I have not gotten it back since. Now, I'll need to pull the chassis and find the bad solder connection(s). I must say that it looked very good while it had a normal picture.

http://i538.photobucket.com/albums/ff341/radiotvnut/2006_0101rca0006.jpg

http://i538.photobucket.com/albums/ff341/radiotvnut/2006_0101rca0007.jpg

Does that one have a service switch on the rear apron? I don't remember when RCA got rid of those, but if has one there's a good chance it;s dirty.
Looking at the second picture, I think I do see a service switch (brown push/pull tab) just left and below the screen/focus block

Hey,
Great ctc-121. Mine was identical to yours. Truth be told, i carted it home on a wagon almost 10 blocks. back in '04 or so.
That Is most certainly a service switch as Geoff described.. and As i recall, the 'inbetween' position of these switches simulates bad contacts..which is loss of luma.
Mine shut down intermittently. Tons of questionable solder joints on the MTT- tuning boards as usual but mine had a filter can which was almost dry. two sections were very low mfd in a simple series test.
My fix for these cans is to just leave the metal canister there, disconnected, and put new caps across the individual sections, with a common.

Amazing picture on this tv. IIRC, The monitor(composite) inputs were A1, A2, on mine whichwas=Ant91, 92 respectively.

I've ran into many of those bad filter cans and I, and most other shops, did exactly what you did. Years ago, someone gave me a varactor knob tuned 19" CTC120 with a bad filter can. The repair shop wanted something like $150 to fix it and they gave me the set.

My CTC121 does not have any A/V inputs. It only has audio otuput jacks.

Yep, have a ctc-120 19" now and the can seems to have held out...really good picture.
I suspect that only some 121-variations had a/v inputs. Mine was ctc-121J ,for what its worth. osd and remote. I don't recall mine having on screen clock, though . But it may have. Like the ctc-130C I have on loan to a friend. These are nice RCAs

If I remember right, isn't this an I Q demod set?

I have a set like this. And the CM7000 box. Thinking I could merge the two, taking the S video output from the box and injecting it at the points downstream of the comb filter chroma-luma filter. Which then should give me a perfect NTSC picture without cross luma/chroma artifacts.

The CTC121 is a hot chassis, so I'd have to either place the box completely inside the TV set, or rework the audio/video inputs my CTC121 has to function as an S video buffer.

I might be able to rework the CTC121's buttons to be wired to an extra CM7000 remote control board, and the output of that either hard wired or IR light connected to the CM7000 box buried inside the set...

Just thinking out loud...

It may or not be germaine to this set, but loss of luma can also be caused by a heater-cathode short in the CRT. On some of these with flyback-derived heater supply, i used to bypass a H-K short by floating the heaters, by cutting a trace on the socket board.

Gently rapping on the CRT neck will generally reveal a H-K short.

Forgot about the possibility of the tube being shorted heater to cathode. I've seen this before and yes tapping the neck of the crt can show you if it's the case or not. Also it can't hurt to touch up the connections on the video outputs(neckboard)...which runs pretty warm.
Bryan, I saw some of the negative comments about this set on the a.r.f. boards and to be fair, I don't think they are justified. These tv's had all the features of the day and were built to last. Also a similar chassis, the ctc-130 was pretty underrated IMO. Heavy yes, but that's a good sign in my book. MILES better than what 'RCA' put out in the 90s in a lot of ways.
It'd be great to find the original remote control for this set--on some website I saw how advanced it was...way ahead of it's time (my set was an April, '84)

Can anyone confirm if the 121 used genuine I-Q demodulation?

I think that model was rather pricey at the time. I had a 25" that had 6X9 speakers on the side of the cabinet. The sound was impressive.

I'm suspecting the service switch, and if not, there are bad connections on the main chassis most likely.

Also, be sure to open up the tuner controller box (MSC001, etc), and solder the pins of the interconnect header that couples it to the tuner. For some reason, it's only the controller module and not the tuner, which has the bad connections. You needn't open the tuner box, most likely. Those ARE cracked, unless it's been done. I don't remember that causing the lumi-loss, but that did cause all kinds of other problems from screen flashing, to snow & drifting, to coming on in the middle of the night, to low volume, and a myriad of other weird problems. Do that first, IMHO.

Charles

I think that model was rather pricey at the time. I had a 25" that had 6X9 speakers on the side of the cabinet. The sound was impressive.

The in-laws had pretty much the same model, I never peeked inside it though but it did have that wonderful audio. That set ran almost constantly up until a few years ago and the CRT had become pretty soft. It did have a few quirks- a strange intermittant width problem that would show up on the right side and the on-off push switches were "finicky" but it was a consistant player.
My late Father in Law was always adamant about owning Zenith products but this set impressed him over what they had at the time which shocked me (and him) that an RCA was brought into the house. He retired from the Ohio State University Hospital (years ago) and used to maintain the TV's, etc. so I took that as quite the endorsement.