ctc-97: Trying to diagnose tuner ghosting

[zenith2134]

I've been having a weirdo problem with my 1980 RCA which has me stumped. After the set warms up the tuner ghosts pretty severely to the point that text on the screen looks like its off-convergence (not a convergence issue though...).

I have the channel-lock feature set to block out all channels except 03 since I run the TV with DTV cable. Interesting thing is that if I press channel up or down, the ghosting goes away for a few minutes. Therefore, if I attempt to change channel with remote or pushbutton, it just flashes quickly and returns to channel 3. This is normal, but I'm wondering if maybe the set doesn't like being stuck on channel 3 all the time? I already replaced the filter capacitor, 3 b+ capacitors and a few resistors on the video output module. It would be a shame to scrap the set because of this silly problem IMO. I doubt tuner modules are available however. Already ran a search on google and found a similar condition with the ctc97, and the diagnosis was to resolder all grounds, which I did.

To be honest, I have very limited experience with digital tuners, especially early ones like this one. Is there something to clean out or anything mechanical inside the tuning box?

[bgadow]

I don't know much about these, only that I have had several digitally tuned RCA sets from that time period and odd tuner issues seem to be par for the course. It's possible I might have some used parts for one of these; others might be able to offer NOS, or the expertise to fix what you have. What you have done already is what I would have done.

[radiotvnut]

It could be a problem on the IF module. That's the metal cased module that is located on the left side of the chassis under where the AC interlock is. If there is an AFT coil, you might try adjusting it. Make note of it's original position and do not use any type of metal tool for adjusting the coil. You might also try freeze spray on various parts and see if that makes a difference. That may lead you to the bad part. Also, resolder any wirewrap stakes and plug in connections inside the tuner, tuner control module, and IF module.

[zenith2134]

Bgadow and Radiotvnut-- Thanks for the quick replies. I'll have some time tomorrow AM to open 'er up and do everything you suggested. Luckily I recently bought some great plastic tools for tweaking my Pioneer SX-1050's tuner section.

Thought I'd snap a few quick shots of the tv in operation (when working properly) to convince you guys it's worth the fix,

As usual, pix don't do the set justice. In fact, my crappy laptop webcamera tends to wash out all colors, like the blue in Marge Simpsons hair and the blue of my cable's guide system. The last pic was an accident, as the station switched to commercial the second the camera went off. Kinda cool.

[MRX37]

Oh yeah its worth fixing.

[zenith2134]

Update: The tuner drifting issue has stopped, but unfortunately its going into shutdown here and there after it warms up. I went over all of the pcbs with my magnifying glass and found no cracked solder.... I may just have to throw in the towel with this set...even though the crt is still strong. I changed out a bunch of parts, so its a shame, but problems keep popping up.

There's very little info about this chassis on the web, and I couldn't even justify buying a manual...The euras database lists this chassis as intermittently shutting down, but doesn't list a component which fails nor a service tip for this issue.

[radiotvnut]

The guy that owns the TV shop that I raid has a tech tip computer disk with a lot of these older chassis on it. I'll ask him to look it up. Erratic shoutdown could be just about anything!

[Findm-Keepm]

Here's what I have for the CTC-97 - there are a couple that address shutdown problems. Hope it helps.

Cheers,

[Findm-Keepm]

I found some more info on the CTC-97. Hope it helps as well.

Cheers,

[zenith2134]

Findm-Keepm,

Thank you! Good literature. I'm going to dig in soon, as it stands now the set has been on and all has been well for the last 2 hours. Again, thanks!

[zenith2134]

Thanks to you radiotvnut also, I missed your post before when I replied.

[roundscreen]

If the color stays on when the picture starts to ghost, The problem is the delay line. That was a common problem with the rca sets made in the 80's.
Ed

[zenith2134]

I don't know how to wind a new delay....maybe I can find a whole new tuner board someplace. I'm going to ask around at all of the old tv shops in town.

Had some free time this afternoon so I'm about 50% done replacing the caps and resistors mentioned in the literature under 'shutdown'. I need to order a lot of new parts as I'm running low.

What I did do was re-set the crt r/g/b bias and the green and red drives. When i resoldered the neckboard, I must of fixed a previously unknown problem with a weak green or blue output drive, because the greyscale got weird and I noticed i had the red bias down near zero beforehand. Now I have actual blues and an even greater picture on this badboy!

[roundscreen]

Originally Posted by zenith2134

I don't know how to wind a new delay....maybe I can find a whole new tuner board someplace. I'm going to ask around at all of the old tv shops in town

Here is a picture of some delay lines. They are the black things with the crooked arrows pointing at them. You will find them on the video panel and IIRC they are blue or black in color in the rca sets. Most of the time you will see the color or sound go out if the tuner is drifting. If the color and sound stays on when you see the ghost in the picture I would bet the delay line is bad. Another test you can do is wait till the set acts up, Put your fingers on it and gently push down. The ghost will go away for a wile and then come back.
{Please be careful when working on a set when it is on.}
In layman terms, The delay line slows down the video information so the video and color information get to the picture tube at the same time.
Ed