|
Looking at the sch, (assuming the 2 red "X"s are connected, elswise you would get nothing.. The "red" 8uF is in parallel with C16, and the input filter C14 is open. If you moved the minus of that 8uF from ground to the bottom blue "X", I think you will find the hum much reduced. C15 is likely to somewhat resonate the filter choke, also reducing hum. I'm guessing the 600 Ohm inductor is the speaker field, and the 70k Ohm heads to the output tube grid resistor for bias.
|