[rcfox]

I inherited a stereo amp from the 70s, and I'm pretty sure one of the capacitors has gone bad. I've managed to find a schematic and PCB layout for it (remember when service manuals were a thing?) but I've been too worried about discharging capacitors to poke at it.

For now, I just deal with a mains hum that's only audible when nothing is playing.

[throwanem]

Amp power caps aren't usually bitey enough to be dangerous, although they will certainly hurt if you're careless with them. They also usually have bleeders, since a line-powered unit doesn't need to economize on power the way something like one of my flash heads does. I usually just poke a screwdriver across them when I'm doing a recap job, and I've never had them so much as spark. But for maximum caution, I'd use a 100K or so 1/2W resistor, connected with clip leads across the capacitor leads, and left for a minute or two prior to desoldering.

For an amplifier of that vintage, I'd probably be more worried about the fact that it'll likely be neither grounded nor double-insulated, meaning it's possible for an internal isolation failure to present a potentially lethal line potential on any metal parts of the case.