1964 Fender Bassman

Repair of a 1964 Bassman installed in a non-original cabinet with three 10-inch speakers.

Condition as received

The amp hummed and made other unusual sounds. Plugging or unplugging a guitar, or moving the cable at the input, could produce a loud pop.

Inspection and work

I checked the effective speaker load in the existing wiring arrangement against the output transformer. It matched. I replaced the input jack on one channel and reverted the non-original grounding to the stock scheme.

Final check

The cable-triggered popping was gone and the amp was back to normal. Its noise floor was lower than when it came in. I did not isolate a separate cause for every sound the amp had made.