Quote:
Originally Posted by DaveWM
I will have some more videos later tonight. I found what I think is the issue on both the vert size and the hum, but alas I did not have the correct cap so had to order, will be a few days before I know for sure.
I did manage to re rivut the speaker (they ALWAYS break) terminal. I also replaced a hacked in wire fix on the chroma board (again a common problem).
a resistor from the boost voltage 150k had drifted up to 2.4 meg, pretty sure that will take care of the height.
an 80uf decoupling cap off the vert out was completely open, this would allow a huge spike to go back into the B+, and mixed with the reg ripple (almost as the vert rate is slightly slower than the line rate) should account for the very slow hum bar. Note the hum bar being VERY slow is a hint here as its the beat of the 59.99 vs 60hrz that is what I think I was seeing.
anyway that all for now.
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I had a Sears Silvertone roundie color set (CTC12 clone). It also had the slowly-moving hum bar in the picture the last few weeks of its life (had other problems too--convergence, etc.), but I didn't think it was a capacitor causing the hum at the time. I tried replacing the 6AW8 video output tube, but the replacement, from my junk box, had a bent pin (!) and the socket broke out of the video PC board when I pressed a bit too hard on the tube.
If I had known that a defective capacitor could cause this problem, I'd have looked at the chassis, and been a lot more careful replacing the tube if the capacitor were OK. I wound up junking the set when the PC board broke, as I was in no position at the time to do any kind of underchassis work (long story and OT).