I'm not sure if this is in the correct forum or not, because this isn't quite as technical as the other topics I searched through, but hopefully this one will do.

I've got a friend from work who's son has an amp that is not working. I don't know a whole lot about amp repair, but I know how to check diodes, transistors, and simple stuff with a meter (no oscilloscope at my disposal unfortunately), so I am just taking a look at it for him. I dont have a whole lot of description about what the amp is doing, but from what he tells me, the amp will come on, won't go into protect or anything, but the subs will pop and them hum continuously. The first thing that came to my mind is RCA plugs or a ground problem, but he had another smaller amp that he put in and it works fine.

Just from this information, is it possible to have any idea of whats going on, aside from a grounding problem (which I can't check since I don't have the car)? could this be a MOSFET or a transistor something like that, or would I just be wasting my time with checking those? All of the solders look solid and nothing is burnt, except a spot on the board around a jumper connected to ground, but this guy tried to solder it in himself so it looks like maybe it was rosin or flux.

I realize that isn't much information so I don't expect much back, but if someone can point me in any direction that would be great. Thanks

I dont know but I will give you a bump to get some more eyes on it.

Pictures would help of the ground that was soldered on to see if it is a problem or not.