OK, you guys ever hear of Occam's Razor? Simple solutions are better than complex ones, but that was definitely NOT the case here!
The set had not 1, not 2, but 3 different problems so no wonder it's been kicking my ass all over town for the last few months.
As indicated by the title of this thread, I had been leaning towards a video IF problem. I therefore swapped in the tuner from the CT-100 today, to see if the problem got better. In a strange twist, it got much worse! It completely lost sync, nothing I did made it any better. Only thing I could think of was a weak or shorted sync seperator tube, and sure enough it got much better with a new tube. I put the original tuner back in and it worked pretty well, but the faint noise pattern was still creeping up the screen. That turned out to be a bad balun, I removed it and now had clean video when making a direct connection with the pattern generator.
That's the first 2 problems, the last is a slight 3.58 dot crawl. I am confident I can cure that by adjusting the trap in the luma path, so I'm gonna call this one fixed for now. These 3 different problems had me chasing my tail for a long time, no doubt they would have confused a lot of people. I'm just glad it's over now, so I can go back to enjoying this nice set.
As an aside I had also taken current readings from the different circuits during the course of this sharade, bouncing them off the CTC-2 to see if there was excessive current drain- there was none, in fact the CT-100 draws more! But the hot ballast still makes me nervous, so I'm going to build a duct to direct a stream of cooling air at it. Probably being paranoid, but cooler is always better.
