[tom.j.fla]

Not to put words in to Tom C.'s post, I think he meant leakage between the heater and cathode of a tube. most likely are the 12SN7 vertical osc. 1st audio amp and maybe the 25L6 audio output. Swap each tube one at a time to see if it helps. Heater cathode leakage was fairly common in the days before controled warm up tubes and still fairly common after but gut better as the technology got better. All so check lead dress (placement) of any leads that carry line voltage keep them away from the high gain audio stages. All the best, Tom