I second Timothy's request -- please do keep us posted on further progress with this set. I had a Silvertone roundie TV in the 1970s with, I believe, an RCA CTC12 chassis, just one model up from yours. Mine didn't have as good a picture as yours does, though. I was just starting out with color TV at that point and didn't know a lot about it. Shortly before my set bit the dust when the video output tube crunched through the video PC board, however, I also had color sync problems that would disappear when I'd turn the tint control rapidly from one end of its range to the other, at least until I changed channels.
The other problem this set had that I never got a chance to correct (the video circuit board broke when I was trying to replace the video output tube) was a hum bar that floated up through the picture. That was actually why I wanted to replace the 6AW8 video output, as I thought the tube must have had a heater-cathode short. The tube with which I was going to replace it, however, had a bent pin, so when I tried to plug it into the socket, no luck. Thinking I could get the tube in the socket anyway if I fiddled with it long enough, I tried again, with a bit more pressure on the tube. That was when I heard the fatal "crunch" as the video output socket (with the tube part way in) clunked to the bottom of the set.
