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I would not describe this as hum from what I saw when I was at Nick's - more like noise bars, which could be rectifiers.
Edit: also, there's some noise that seems video related, like the video or IF is radiating back into the antenna. This all goes away when the input is baseband into the first video.
Also, the voltages Nick reads show a much greater drop across the ballast resistors than what SAMs says, if I recall correctly, which would explain the excess heat. That says there's some kind of short, but finding it has been difficult. If it's in the IF or tuner, it might be possible to isolate it by resistance readings on the tube pins (as compared to the SAMs resistance chart). It's too bad SAMs doesn't have resistance readings from the pins of the ballast socket, which would isolate it to one branch or the other of the B+.
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