Fender Deluxe 112

[gbono]

Replaced J1 since it was intermittent but the amp has a loud 60 Hz buzz at the output terminal CP1/2 ONLY when (different) cables are plugged into J1 or J2. I measure 4-5 mV (CP1/2) without a cable connected to J1 BUT .1 VRMS with a cable connected. The PS ripple at TP3 is .2 VRMS. Also noticed a loud pop can be heard when turning off the amp.

This isn't related but why does J1 have pins 1 and 9 connected but on J2, etc. pin 9 is always a NC??

[DrGonz78]

Have you tried cleaning the headphone jack? Also, what do you mean "ONLY when (different) cables are plugged into J1 or J2"? I guess you are saying the output does not hum when something is plugged in to the input. One more thing... Do any of the preamp controls make any change to the hum when you move them around?

[52 Bill]

Don't forget that this amp has a mute that kills the audio signal unless there is a cord plugged into one of the jacks. So the hum that you are hearing is either coming from the cord or from the circuit before the mute fet circuit.

[g1]

Like 52Bill said, you are comparing to the muted circuit.
I assume the other end of the cable is terminated?

[gbono]

Thanks for the replies - the issue turned out to be faulty wiring in the mains socket where the amp was plugged in.

Another issue with the amp was a buzzy speaker which appeared to have an off center or over heated VC. The problem was the dust cover on the cone was not completely attached.