Peavey Nashville 112 hum.

[Andre Dardeau]

I have an older Peavey Nashville 112 that has been dead silent since the day I got it. Recently it’s developed an audible hum that is somehow linked to something rattling on the cabinet. Here are the specifics: It starts about 45 seconds after the amp turns on, continues to be audible in the room after putting something in the headphone jack, and to my fingers and ear doesn’t seem to be coming from the speaker. I tightened the obvious stuff, any tips?

[Andre Dardeau]

The buzz is definitely coming from the speaker, which is the only thing I haven’t tried changing. I’ll give it a go tomorrow morning. I’ve cleaned all the connectors with jacks with contact cleaner. I have noticed the pitch changes when I insert a jack in the footswitch so maybe the middle ring needs retensioning?

[Andre Dardeau]

Another thought, it wouldn’t be anywhere on the board with the pots on it because none of the controls effect the buzz?

[Andre Dardeau]

Can confirm not the speaker, or an external rattle. I was wrong, it is definitely coming from the speaker, not tied to gain, not stopped by patching any on the various effects loop. The only thing I can find that changes the noise is plugging a jack into the footswitch input, which changes the tone of the hum.

I’m so frustrated, this was supposed to be my reliable amp for when my old amps are doing old amp things. At least the bass player quit so I don’t have any commitments.

[Jamie Howze]

I have the same issue with my older 112. As I recall, the controls don't have much effect on the buzz. I mentioned it to an amp tech once and he described it as a bad diode near the heat sinks. I have the schematic, but have been unable to locate the diode.

The delayed onset seems to indicate it's temperature related. It may require an amp tech.

[Dale Foreman]

Pull the reverb tank loose from the connector above the speaker. If the hum goes away, replace with a mod 3 spring reverb tank.

[Richard Sinkler]

Pull the reverb tank loose from the connector above the speaker. If the hum goes away, replace with a mod 3 spring reverb tank.

The 112 doesn't use the Molex plug like the 400 did. It appears that the wires come straight out of the chassis. I reached up where the reverb wires meet up with the chassis (can't see there without pulling the chassis) and feel no plug. It's been a while since I had the chassis out.

[Andre Dardeau]

There is a molex type connector inside the chassis, I’ve cleaned it. I’ll try just unplugging it. Any other ideas would be welcome, I tried to take it to the tech today and he doesn’t work on solid state amps. I’ll try the other tech in town tomorrow.