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Well, today there were several steps forward, and one big step backwards.
Was still having trouble getting the chroma reference oscillator to lock properly, and then figured out that I had a grid emission problem on the 6AN8 in the oscillator. A voltage check found the grid of the reactance tube much too positive given what the circuitry around it was doing. After swapping that tube out (it looks fine on a tester), I was able to lock the chroma oscillator. At that point, I had lots of wild colors on the screen, and got busy with alignment of the chroma bandpass filter and various other tuned circuits in the color demodulators. Then worked on purity, which was only so-so around the edges (maybe I need a degausser?). Finally installed the new convergence transformer. While setting up to do convergence adjustments, I adjusted the width, height, linearity, to get a nice looking crosshatch on the screen. So far so good, and then...
I heard a gentle pop, and the picture went dark. Very quickly took a look at the flyback, and low and behold, the tape holding the 3A3 anode lead in place had actually caught fire! Obviously an arc occurred (maybe triggered by my changing the width setting?). Quickly blew out the flame, and then pulled out the flyback to see what condition it was in.
Quite surprisingly, all windings good, and no shorts. Good ringdown. But it would obviously arc again without repairs. I unwound a few layers from the outside diameter, and am coating with corona dope and varnish while I contemplate what to do next.
There were significant problems running things with reduced HV because of the turns I previously removed from the flyback, so simply getting back to where I was earlier today probably isn't a real solution.
If I add more turns to this flyback, I wonder if it will arc again? Doesn't look promising.
Maybe tomorrow I'll try a voltage tripler running of the primary of the flyback. If I get enough voltage that way, I can remove the HV winding entirely. If I don't, maybe I'll unwind most of the HV winding, leaving just enough to run the tripler?
I wish there were someone out there with a spare flyback or a junker chassis or set. That would be a much more straightforward solution. But there might not be any spares out there that people are willing to part with.
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