Color Problem in RCA TV

[Rebuff]

I've been working on an RCA television which has the CTC35C chassis. A problem showed up pertaining to the color. And I have been assuming that it had something to do with whatever was going on in the chroma board.

The TV has a perfect black and white picture with normal sound. But when you go to turn the color control up, all you see are these rolling color bars going up and down the screen.

The color does not seem to be locking into the correct sync with the black and white image. I went ahead and replaced all six of the 1N34A diodes on the circuit board with brand new ones.

And I did notice as I was removing them one by one and testing them, there didn't seem to be anything wrong with the old ones. But I put the brand new ones in any way. And the problem is still there.

Then I replaced both the 6JC6 and 6GH8A vacuum tubes. No noticeable difference with the picture at all. The heaters in all the other vacuum tubes on the chroma board seemed to be coming on normally .

Only other thing I haven't looked at just yet is the 3.58 megacycle Crystal underneath the circuit board. I'm not sure if that could be faulty. But I did go ahead and order the exact original one anyway.

Yet I'm not sure if there might be other major problems with that chroma board itself. I'm still not giving up on anything here as of yet.

 

[Nigel Goodwin]

Have you tried adjusting the trimmer on the crystal?, it looks like the PLL isn't locked - it could be the crystal, they do (or did) go duff. Not that I've ever seen an NTSC crystal, but PAL ones failed. Even if it won't lock, you should be able to adjust it very carefully until it's 'almost' locked, and if so the crystal is probably OK.

 

[Rebuff]

The crystal that's in there looks like it might be one of these types that's not adjustable. Next time I'm free and I get a chance to take the TV apart again. I'm going to look into that. Thanks

 

[Nigel Goodwin]

The crystal that's in there looks like it might be one of these types that's not adjustable. Next time I'm free and I get a chance to take the TV apart again. I'm going to look into that. Thanks

Crystals aren't adjustable, but they usually have an adjustable capacitor next to them to adjust, and particularly so on such an old set.

The service manual should give instructions how to set it - usually you disable the colour killer (your one might be too old) and disable the PLL.

 

[charlesli]

The crystals appear to be non-adjustable.

 

[Nigel Goodwin]

The crystals appear to be non-adjustable.

In which case change the crystal, however it 'may' be a slightly unusual type as they don't provide adjustment for it. Stick one in, and see what happens

 

[Rebuff]

I'm going to take a look at the whole thing next time I get it all apart again. They have this crystal underneath the circuit board and it's soldered with two wires connected.

And there is a color killer adjustment control on the back. The replacement crystal I ordered is the exact same replacement RCA crystal with the same number.

We'll just have to see what happens after I take another look at it.