RCA 630 TS Picture Drift

[M3-SRT8]

My 630 TS is up and running, and looking great.

The pic drifts to the right after a while, exposing the black mask on the left side. I swapped out the 6AL5 and the 6 AC7, but, it still drifts.

Any ideas? I'm thinking it might be the two 470 K ohm resistors (R191 & R192) located on V123, the 6AL5. They look fine, so I didn't replace them during the resto.

Any Ideas, Gentlemen?

LJB

[Old1625]

If tube swapping doesn't fix it then your next step is to check for adjunct components such as the resistors you mentioned. They may have drifted enough in value to cause trouble. If it tends to happen after the set gets hotted up then I would tend to want to blame a capacitor. You may have recapped the set, but it isn't impossible to have a baddie in the new lot. In replacing frequency-critical capacitors you need to be sure that aside from its mF and voltage ratings that the new one has the same temperature coefficient as the original. If the device you put in has a "temp stable" characteristic, and the original had an "N750" designation then you could run into trouble after warmup. Caps with such coefficients were used to compensate for the natural tendency of a circuit of given design and component choice to drift out of tolerance.

The other thing you might want to examine is that the aquadag coating on the CRT (if this is applicable) may have become ungrounded. A horizontal sweep pulse can electrostatically emanate from an ungrounded CRT and raise hob with sensitive AFC circuits.... just a thot....

[M3-SRT8]

Yeah. The .015 and 1200 mmf caps that are part of the synch discriminator control were replaced. I have the ones that came with the set. They, too are replacements, and maybe that have the correct temp characteristics.

I'll try them.

Thanks;

LJB

PS: I think we're neighbors...