Amplifier repair
Unknown model not working could be a bunch of things!
does the unit have power?? fuse(s) ok?? turn on voltage present(12v)?? Any leds?? Unit ever get wet?? Any lites?? smoke get out?? was it, did it get real hot??
I have worked on a few with various problems, no common problems. Some of the things I have seen; Level adj pot was smashed in, Shorted fets , + burnt gate drive resistors in the ps section + blown runs, bad connections, shorted outputs, corrosion from beer leakage, bad electrolytic caps, leaking caps ate up the copper runs, metal bars used to hold down fets and outputs came loose, parts over heated and shorted.
Open up and look around, burnt resistors, leaking caps, puffed up caps, black marks, are all helpful signs.
These amps typically use FETs in the power supply(+/- 25-50v) and regular transistors for the outputs. Test all heatsinked parts for shorts. Carefully remove metal bars holding down heatsinked parts, keep track of where the heat sink insulators go, remove pcb and inspect runs. Repair and bench test with a power supply that has an amp meter. With out any input, unit should only use a few amps after initial 5-15amps to get the PS fired up. Then test across speaker outputs for any DC voltage. Anything over 1v, (should be very close to zero) amp needs some more work.
Good luck!