Well it could be anything in the circuit.  The 10 year old thread is about an MA104, and you have a MA007.  Are they the same inside?  I don't know.  Can you post a schematic?

Saw a cheap camera advertised as having a "genuine non-achromatic lens".


And I bet the amp is also gluten free.

100% analog?  My how clever.   That simply means there is no digital in it.  Like no DSP or anything.    Imagine I market a TV set with "genuine full manual direct wired controls".  It just means it doesn't come with a remote, you have to walk to the set to change channels.

You have three LEDs - plus power indicator -  A, B, and P?  I'd wager channel A, channel B, and Peak.


I'd check the IC for function

I think the lesson there is don't just flip an amp on and crank a power chord without at least checking the amp.  AANy amp, ever.

I did, it grew.  I had options of huge or tiny.  I like a pdf so I can grab the part I want and make it the size I want.   I'm not complaining, I am just picky.

That^^^^

SOlid state amps do not need a load.  TUBE amps always do.

I can't read yours, but I have the G100-3, which looks the same other than power.

May I suggest, just unplug the speakers?  The schematic and parts layout shows the speakers plugging into the rear panel jack.

And electrolytics do dry out with age, but the little film and ceramic caps should last forever.   REALLY OLD caps like the wax covered ones in really old tube stuff will need to be changed as well.

And I agree, on these little practice amps, it really is unlikely you need to change out the caps at all.

And at the other end?

Feedback is one form of oscillation.  There are others.

The schematic does not show the PA jack tip connected to R1.   The tip is pin 2, which when plugged connects through auxiliary contacts 5 and 6 down to R99, which is the power amp input.   R1 does not connect to ground, it runs through the other auxiliary contacts and then back over to the input jacks.  It is part of the mute circuit.

Disagreements are not offenses  This is a forum, I stated my thoughts and not everyone agrees with me.  That is fine, and that is how we learn things.

2mv hum is not a lot

The JFET is across the signal path.  I just want to know what happens when you short from r59/C33 to ground.  NO need to short the gate.   While the JFET itself can be noisy, I was thinking your noise is either coming into the power amp through that path or it is after that point

I meant the volume on the guitar itself, we were bypassing all the preamp.  I will assume you did that.

That puts the hum in the power amp.  CAn you scope or otherwise measure the ripple on the 40v rails? 

Q7 is the mute JFET at the input of the power amp.  SHort across it, does that kill the hum?  Or remove Q7.  Same question.

If you want to earth it, then earth it.  Peavey made any number of models in the modern era with the two wire power plug, and met whatever electrical approvals they are asked to.  What those are I cannot say.  That was all I was thinking.