back when i was an audio newb i accidentally hooked up the +12V to GND and GND to +12V. It was a Jensen 4 channel amp, and from then on, 2 of the outputs crapped out. It was only powering 2 10" punch z rockfords, so i just bridged the 2 other channels and it works ok. If youre sure all the fuses are fine, especially including the in-line fuse on the power wire coming from the battery, and the fuses on the amp itself...then the only option is an audio shop.