Hi,

This is a 1974 (I think) solid state baby. Came to me with a massive 50Hz hum coming through the speakers. All components in the power supply were replaced, and the power transformer checked and pronounced quite sound. This circuit uses a LC Pi-filter on the output of the diode rectifiers, and the inductor is the component causing the hum. Would anyone have any idea on what I could use to replace that inductor. I don't have a value, the capacitors in the filter are both 2200μF, 25v. Someone did suggest two 1ohm 5watt resistors in parallel with each other, but I am uncertain that is a good option.

I have the full service manual for the 11-157. It should have the value of the inductor in the parts list.

I'll check later when I'm at home.

UPDATE: L4 is listed a H.T. choke with a part number of 4048-025-02 but no other details.

Try tightening the screws holding the inductor together and to the chassis. Or maybe a toothpick to insert between the wire coil and the lams.

I recall looking for a hum in that model when it was new and under warranty.

It turned out to be not a fault with the power supply but something else that was affecting the amp's inherent hum rejection ability. Some sort of common-impedance issue with a ground return.

Sorry, it was a long time ago and I wasn't the one who found the fault. But at least I can assure you that it's NOT the filter inductor. The amp should be hum free with a couple of volts ripple on the supply.