My sister's got a Cube 30 Bass that's in need of repair. It suddenly became really quiet and it's only audible with the volume and gain dimed. The Aux In seems to work alright, but it bypasses all the controls, so whatever's wrong must be in the modelling section of the amp or before it. The input jack seems to be soldered to the circuitboard just fine and if there's a bad connection, I can't find it. Nothing's crackling at all.

Anyway, I've messed around inside of tube amps before, but never SS. I'm assuming there are caps out there that can shock me, but are they as lethal as the big ones in tube amps? Would I need to discharge them before I start going at the insides with a multimeter? And what kind of reading would I be looking for for a faulty component?