So my car's amp has been dead for about a week. It's a Lanzar OPTS 650.5 model. Rated at 1360w max (I think it was like 150w x4 and 300w x1 RMS) 5 channel amp with subwoofer remote level control. It had stopped playing anything through channel 5 (the sub). I took it apart, I see nothing wrong with the board. When I initially got it I had taken it apart and flipped and pasted all of the heatsinks because they were ridged-side down with no paste -_-. Heat shouldn't be an issue due to that and I also have a direct shot into my trunk for airflow - I always drive with the windows down or the AC on. Looking at it again now, I noticed that some solder joints were half-tinned, but I tested each with a voltmeter and they all showed continuity. For the hell of it, I went and filly tinned all of them. No cold joints on it. I've ruled out the RCA cables and speaker wire. I've never seen a speaker go dead to the point where it makes NO sound, so I doubt that the sub is the issue. The only thing, other than the sub, that I haven't tested is the head unit itself (specifically the sub outputs). I plan to hook one of the speaker channels to the sub channel on the amp and drive an old door speaker with it to see if THAT works. Does anyone have any ideas?