New user here, hope this is the right place to ask. I recently bought a powered sub at a garage sale (luckily it was cheap so if it's FUBARed it's not that bad).
For the first few days I had it it was great, loud as hell and shook the room. Then I went abroad for 2 weeks and now for some reason it seems to only output a very faint, small amount of sound. It still works, and the input sensitivity does control the volume, but it's pretty much nothing even at full input sensitivity, whereas before it was earthshaking at 1/4 turn.
When it was working fine there was like a minute where it did this and I just jiggled the connections or something (really not sure what I did) and it started working. Now though, a few weeks later, it seems nothing works. I tried different cables and inputs (I'm using the RCA red-white inputs on the sub). Stuff that i know worked before and worked great just doesn't anymore. The sub just outputs at a low volume. Not sure where the problem is.
I opened up the enclosure and the leads from the amp to the actual sub are fine. I disconnected them and the low-volume thumping stopped, reconnected and it works. Both wires are connected fine on both sides. None of the capacitors seem busted (no protruding tops that I can tell). The fuse doesn't seem broken either.
So now I'm stuck. I've googled this all over to no avail. The sub is an Onkyo LR 104580, at least I think that's the model. I can't find any references at all about it online except for one thread on a forum (can't post a link but its the result from "home theater forum" if you google that model number), which has pictures of the back and the innards if anyone will find them useful.
I have access to Electrical Engineers (the beauty of attending an engineering school) but I don't just want to come up to them saying "fix this amp", I'd rather know what I'm looking for (busted transistor, power supply etc.) before going over.
Sorry for the long thread, but any ideas?