1984 Peavey KB100 Only HUMS

[Jayz]

Thanks for the caution Bill. The diodes in series had no affect. Please tell me where to check for DC voltage. When you say; "....on the output..." do you mean across the speaker output?
Thanks - I appreciate your patience and I wish I knew more.

[DrGonz78]

Clip your leads, for your multimeter, onto each one of the negative and positive terminals of the speaker output. Set your meter to DC volts and do not connect a speaker or load until we have no DC on the output. So yes you have the right thinking here...

[Jayz]

The fuse is an AGC3/250V which I believe is the correct fuse. I checked DC voltage across the speaker output. The reading decays from an initial 6V to 0.5 V within about 4 seconds.

[Jayz]

You are all probably going to laugh but it turns out it was a bad ground on a power supply 2200/50 cap (CR59 on the 1984 schematic). I only did a visual exam of the PCB for bad connections b/c I was afraid to use the "eraser tab" method when powered up b/c of the "hum".
Anyway - replaced the dual diode and all is well! Thanks again for your advice!

[Jazz P Bass]

I am not laughing at all.
Glad that you got it.