help fixing memory man - rumbles when tapped

[varialbender]

A friend of mine asked if I could help him with his memory man.
Apparently, whenever someone would step near the box or do anything to cause it to move slightly, you'd hear a low rumble. It's kinda like when you kick a spring reverb and you hear the springs rattle out. Of course, the cause of the problem itself can be nothing like this.
He took the board out, and it doesn't seem that it's a matter of touching the board at all. Gently touching one spot produces no effect, but a tap hard enough (though still fairly gentle) to move the board a little sets it off. I checked over the soldering, and it all seems fine. I can't see any parts touching, other than a pot and a cap, but the cap of course has a plastic coating and i can't imagine this being the problem. The sound is being delayed, but i don't think the dry is affected (hard to tell), so my guess is that it's a problem in the feedback loop. Could be the input to the delay though, there's a chance the dry was affected.
Anyone have any ideas? Any similar issues you've come across?
I know it's tough to debug such a problem without having the board to look at, but I figured I'd toss it out there and see if anyone can help.
Thanks a lot,

Alain

[MikeH]

A lot of the time that low static-ish rumble can come from a capacitor drying up that needs to be replaced.  Usually in older effects and amps.  Why that would get triggered by some sort of impact tremor, I have no idea.