Fixing combo rattle

jim_cross

I recently picked up a Morgan SW22 (lovely amp!), which has a fairly prominent rattle. I don't notice it in a band situation, but do notice it playing by myself, even at close to rehearsal volumes.
At first I assumed it was tube rattle, but then I heard a rattle when I was plugging in the power cable, which I also hear when tapping the bottom of the chassis. I think it might be a loose screw/nut/whatever in the circuit.
Is there a safe way to track this down myself, or does this need an amp tech? I'm quite keen to avoid electrocuting myself or blowing up the amp, but a trip to a tech seems like a pain for what could be a loose nut

ICBM

Just turn the amp off at the wall without using the standby switch first, unplug the power cable, wait a couple of minutes to be sure, then it will be safe to open it up. Use something insulated - chopstick, plastic pen or something like that - to poke around. If the whatever is loose is obvious enough to be disturbed by plugging in the power cable it shouldn't be too hard to track down.

jim_cross

Thanks @ICBM - having taken the chassis out it was quickly apparent that it's a super rattly valve