Quote:
Originally Posted by old_tv_nut
Could you explain a bit more about the vertical capacitor selection? I don't seem to have a significant drift in linearity with warmup, but it's nowhere near perfect either. I'd have to look again, but I think when the top and bottom are symmetrical on average, the very top is pinched a bit, and there is a noticeable transition near the center of the picture that's visible with vertically scrolling titles. Replacing tubes helped, but didn't totally fix it.
My set has developed a brightness drift - too high when first turned on, drifts darker over a minute or two.
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I discovered in my set a number of resistors that drifted badly with heat. I replaced quite a few with NOS carbon composition resistors and and it addressed a number of issues including the brightness drift you described. Perhaps it was just a bad batch of resistors? The replacement carbon resistors do not have the same problem.
As for the selection of the capacitors in the vertical sweep circuit, I was plagued by quite noticeable linearity and height changes in the vertical sweep circuit. I found a number of drifting resistors here and frustrated with it replaced all the resistors in the circuit. It was much better but there was still an minor annoying change in linearity as the set warmed. I recall replacing C512, C513, C508, C507, C511 and C504 a second time to address it. These were all new DigiKey replacements I was obliged to change again with another brand of capacitor and I cannot recall the specific one. But once addressed, the sweep linearity is excellent and there now no noticable change as the set runs.
It just seemed odd to me that despite the capacitors testing good I could not identify the chacteristics of the capacitor change with heat that affected the sweep.