Odd idle Hum for Peavey Classic 30

[TubeD3]

Has anyone encountered anything like this before? It occurs whether I plug in to another power source, use a brand new cable and reposition the amp in any variety of ways. I swapped the tubes into new spots to make sure there were no easy fixes like that. The one thing that is interesting is that changing the pickups on my strat to one below neck and one above bridge makes it almost go away (see in 1st video). Thank you in advance for your help!

[Enzo]

Please describe problem in words. In your vids I hear you playing, and between plays I hear an occasional hum.

If switching pickups on the guitar changes the hum, then it is not likely in the amp. Is your hum present with NO guitar plugged in? And if you plug in but dial the guitar to zero volume, is the hum still there?

[Delta362]

Sounds like you are picking up single coil hum and when you drop a notch, you're putting your pickups in humbucker mode which will reduce it greatly. Got any dimmer switches nearby? Fluorescent lights? Cell phone?

[TubeD3]

Hey Enzo, thanks for your response. The sound seems to dim while playing and it does occur with the guitar unplugged and no plug in amp. Same if the guitar is set to volume zero. This amp has an auto stand by and the hum comes on immediately after the stand by retreats even when nothing is plugged in. What's odd is that I had it in storage for a couple years and there was no hum last time I played. If I turn on the gain channel the hum is obnoxiously loud!

[drewl]

With all the gear in my lab at home, even if my test guitar is near anything with a transformer it will pick up hum from the gear around it.

Same with test reverb tanks.
Spent a while trying to diagnose reverb circuit hum only to realize the tank was next to an on soldering iron, turned off the iron, hum went away...DOH!

[drewl]

There's an FX loop on these, right?

Plug in to fx return. If hum is gone, problem is in the preamp.
Hum still there, problem is in the power amp or power supply.

[Chuck H]

What's odd is that I had it in storage for a couple years and there was no hum last time I played.

I think I interpret that the hum comes and goes? If this is the case I might not suspect the power supply right away. Rather, because it sat unused for years I would suspect oxidized contacts. This would be any jacks, pot wipers, tube sockets, etc. Always start with effects loop jacks. NOTE: Contact cleaner and potentiometer cleaner aren't always the same thing so be sure to use the right products in the right place.