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I didn't list everything I had tried yesterday afternoon. Poking stuff with a stick was the 1st thing I tried.
2nd I checked the 22-5001 caps. I had replaced the white ones with the orange drop ones along with a bad tripler a few months after I got this set back in 2010. But then I had one of the orange ones short on me last summer, and I remember it doing this the day before it shorted. So I pulled one end of each cap out of the circuit and clipped in another one, then looked to see if it made a difference. In the process of doing that I did find one of the grounds two of them hooked to to be loose, but resoldering that didn't fix the problem completely.
Then it was when I was swapping out the ones on top of the chassis that I noticed it went away, and I thought those 2 caps must be bad and that I had fixed it …. but it came back. Eventually I came to the conclusion that it didn't make any difference whether I had the new orange caps clipped in or the orange ones I had already had in there, but clipping those alligator leads on the connections on that board was having an effect. Sometimes starting the trouble, sometimes stopping it. That's when I resoldered everything on that board, and that seemed to make a big difference, but didn't fix it completely.
Today it wasn't doing it at all for a long time, but when it finally did I took the back off. I checked the voltage on those grounding straps and got between 500-1000V. And now that I knew where to listen, I could hear some soft hissing coming from the CRT socket. Because there wasn't any obvious corrosion (like there was on my 25MC33 that had a bad socket) I didn't bother to take it apart yesterday. I took it apart and there was no corrosion, but there was some black gunk on the plastic in there, which I cleaned off. Now I get no voltage on the grounding straps, and I don't hear any hissing, so I think that fixed it.
And just in case, I also cleaned off that flyback board, and resoldered the connections on the tripler. Then poked at the rest of the terminal strip grounds while watching in a mirror to see if it had any effect. I think it's fixed, but this was weird because it was one problem with 3 separate simultaneous causes.
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