Blues Jr. Sypathetic Rattle In Reverb Signal

[critter74]

I just recently got a new Blues Jr. III. I'm running it through the paces to see if I like it etc. So far so good.

Anyways, I have a weird reverb issue that isn't like any of the other reverb complaints about the Blues Jr.

In short, it only happens when I hit a B note (any pitch), so it has to be some sort of sympathetic frequency response. What happens is when I hit a B note, as the reverb trail is dying off, there is a weird rattle type noise. It only happens in the reverb signal and it only happens on B notes (any other pitch does not cause it and if the reverb is off it doesn't happen but becomes more apparent as the reverb is turned up). And it is the B note frequency itself as I can actually be a whole tone down, have no problem but then bend up to pitch and hear the issue. So definitely either the fundamental note or one of the order of harmonics is causing this sympathetic response...

So, what could it be? If I decide to keep it I'm planning on upgrading the reverb tank anyways. But I want to try to see if it is that before I decide to keep it. I've replaced the pre-amp tubes and tightened down all of the screws to the cab and chassis, so its none of those.

Any help would be appreciated.

[critter74]

Anyone got an ideas on this?

[Birdseye]

I would suspect something in the tank. A broken or loose spring would do exactly that, rattle at certain frequencies.

[Crowbar]

Hmmm... that is weird. I might try isolating the tank somhow or another, like put a piece of soft rubber or bubble wrap under it so it dosn't feel the vibrations? Turn the amp on its side and see if it still does it. Then maybe you'll know if the problem is in the tank?