Peavey TNT 115 Scorpion constant Humming all the time

[bowtieman427]

New to me used older Peavey 115 Scorpion which has back ground humming (sounds like 60Hz humming) all the time which is very noticeable at about conversation sound level... The humming is constant and does not change with any switch in or out or level/side or adjuster nob position or when the bass is plugged in to either jack. There is some scratchy/static noise from switched, level/sides adjuster nobs switches, but I think they just need cleaning and unrealated to the humming.
I have not taken it apart yet.
There is a 3 position rocker +, - and 0 ground switch in back and the humming is unchange in any position. It is always there no matter what I do and remains unchanged.
-I have a Fluke DMM
-Solidering iron
What is the the best logical way to go about looking for the issue and fixing the problem ?
Where do I start ?
What do I look for ?
I have a schematic for 115S found free... Will this work ?
thanks Jim

[Jazz P Bass]

It very well may be power supply ripple that is causing the hum.
Find the power rails & look for Volts ac ripple riding on the Vdc.
That would indicate , if found, a faulty power supply capacitor.(s)
I would also check the +-15 volt supplies for the same thing.

[bowtieman427]

Thanks give me a few days to take it apart and I will check. It may be best to get it apart and start checking points and report findings back on this thread.

[AEB-1]

The problem with the Peavey TNT 115 Black wido and Scorpions is due to corrosion between the chassis and and the aluminum standoffs for the preamp PCB. Peavey grounds the PCB through the standoff but the corrosion causes resistance in the connection. Look for the satndoff that has a PCB circuit going to it ( I think it's the corner or the next one in). Remove the standoff (drill rivet), sand the chassis where the standoff goes and replace the standoff. The amp will be dead quiet if done properly. I have done several of these amps with great success.