Fender Excelsior Hum

[MrNovember]

So I have a Fender Excelsior amp, which I love, but it's been humming for awhile now. It doesn't always do it and when it does I usually just pound the top and it goes away; sometimes for good, sometimes it comes back shortly after. It's pretty annoying.

I've been meaning to post about this for awhile, but I wanted to post some audio clips. Unfortunately, I haven't been able to capture it at all in a recording.

Anyone know what's up or how I should go about fixing it?

Extra details:
Guitar is a Fender Blacktop Jazzmaster with a Gibson Dirty Fingers humbucker - I don't think it's the guitar, it did the same with old guitars
Pedal chain: Polytune > Fuck > CT5 > Secret Destroyer > Dispatch Master > Ditto > RM-1N > MXR 10band EQ (all daisy chained except the EQ, which requires a different voltage)

[friendship]

Might need a power tube swap. Got any spares lying around?

[MrNovember]

Might need a power tube swap. Got any spares lying around?

Nope, but I'll pick some up after work next week. That would be sweet if that's all it is. I was kind of planning on doing that at some point anyways

[crochambeau]

Does it, by chance, require firm mechanical connection of jacks and so forth for a ground plane? Might just be a matter of cleaning & tightening stuff.

Another thought is if it has a switching jack as a send/receive, might be overdue for a clean (this also results in an apparent loss of power while playing).

In my experience, if you can reliably slap it to make it go away the problem is mechanical, not electronic... and the first point of suspicion is the ground, which will make it hum.

[rfurtkamp]

Tube amp 101: Swap tubes.

Does problem go away?