03-28-2020, 12:41 AM
60hz hum? Should be 120hz. If actually 60 hz could be the 80 is out of balance... Were any of the wires to the output transformer swapped? That would defeat the hum bucking system.. There could be heater cathode leakage in the 75...
GL
Chas
GL
Chas
Pliny the younger
“nihil novum nihil varium nihil quod non semel spectasse sufficiat”