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Hi Stan
I had one of these years ago (with the Phonevision socket), and I almost burned up the flyback the day I got it. I'd only had it on for a few minutes when I heard a crackling sound. I ripped the back off only to find the flyback coating drooping in chunks, like the chocolate on an ice-cream bar that got too warm. I found one of the caps in the damper circuit had leaked down to less than 50 ohms. It was one of those "bumblebee" caps that ironically, folks elsewhere on this site go nuts over. Please allow me to offer a few hard-learned bits to you:
Did you measure leakage on each one of the caps you replaced before you installed them? All the (no matter if new) tubes tested OK? Did you use a de-oxidizing product on the tube sockets? Did any resistors change value AFTER soldering new caps to their tie-point?
Nothing beats a good brand of replacement parts. I often disagree, as gently as possible, with folks on and off this site about their choice of (el-cheapo) replacement parts. You have a hard-to-get flyback in that Zenith, and it would be a shame to lose it (or another unobtainable part) due to a financial misunderstanding. All the caps that are part of the circuits in question here should have a superior dielectric characteristic. A cap rated at the required voltage or higher may do fine for bypass work, but in horizontal-pulse circuits, the B-boost and yoke-coupling caps take a beating, and that same cap can soon overheat and fail...Use caps specifically qualified for use in "snubber" circuits and you'll be safe, and the kid at the parts counter will actually understand what it is you need. My personal choice (if available where you shop) is Sprague's 715P series, worth every extra penny.
Lastly, I you have a 'scope, look at the drive signal at the .001 cap just after the Phonevision socket. If this socket or the jumper-plug gets corroded, then disturbed, you might lose signal. Also have someone else check your rework. You may have simply overlooked something or have solder-adhesion issues. Really get in there and look hard. Good luck!
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