Roommate's Sub blows fuse, like dead short blown. Board inspected, nothing apparent, no smells. Next step, light bulb hacked into an extension cord in series(current limiter), fuse bypassed with Al foil, lights bright, I expect the shorted component to heat up now, it doesn't. Steal the big 150 watt bulb out of the shower, rectifier gets warm(its looks like a switching PSU). Replace rectifier, same symptoms. I tested it after removing the rectifier and got nothing, so whatever it is, its past that point. We're quickly approaching the point of buying a whole backplate making economical sense.
When in doubt, test voltages. Are there silkscreened test points on the boards, especially in the power supply section? If not, you're going to need a schematic.
Chinese backplate, no schematics available, minimal silk screening(no psu boundary lines or anything helpful like that), hence jumping straight to the poor man's variac. I'm not real familiar with switching PSUs.
If it's not a high power amp, I'd consider one of the plate amps from Parts Express if you don't feel like dealing with that one.
Honestly, it's probably got a couple of dead caps. Does your meter measure capacitance?
No cap tester, the two big filters LOOK ok, I'd figure any of the smaller ones would go bang with 150 watts on them. I'm tempted to screw a 15 amp plug fuse into my current limiter socket and see what gives first.
Do you hear anything out of the speaker (hum, really bad hum, hiss, extremely low volume signal, etc)?
Never heard anything blowing 4 fuses before we took it apart.
