An apology is in order. The transformer heater supply is not centre tapped. The twisted red wires go to the octal tube sockets pins 7 and 8 and all the pin 8,s are earthed via by a thin black wire to pin number 7, on the nearest 6C33C-B socket, which in turn is earthed via black wire that goes to the earth star point which is linked to the chassis ground via a 5 ohm resistor.
For the 100 ohm resistors to have any effect in reducing hum, there would have to be alterations made to the wiring.
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For the 100 ohm resistors to have any effect in reducing hum, there would have to be alterations made to the wiring.
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Life has conspired against me getting anything done on the amp this week, I'll probably have to wait until Saturday for more experiments.