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Not much progress - instead of pulling the chassis to inspect the blue convergence coil, I did some playing with video sweeps, and while in the process. the set developed a horizontal instability that I can't diagnose so far. At first I thought the AGC or tuner might be involved, but I can turn AGC down to a low-contrast picture and the problem remains the same.
Anyway, the horizontal phase became jittery, and occasionally drifts out of sync entirely. I've tried tapping on things and wiggling tubes and wires, and tuning off channel and back, but haven't found anything that causes it. Also tested tubes (although I don't have subsititutes for most), and all in the sync/AGC/horizontal check OK.
Not sensitive to line voltage either. It did seem to clear up by itself for about 30 seconds after warmup when the set had been off for 10 minutes, so I may have to chase some thermal problem.
These old sets do have "personality!"
Any suggestions gratefully received...
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