hi my road thunder RT251D amp for sub has all of a sudden stopped working, the amp to power speakers shows the power signal and is working fine but this one isn't and shows no sign of power.. i checked to fuses and seen they were fine but i still changed it anyway and also since this amp stopped working i have no sound coming from any of my speakers, the sub also doesn't make and signs of working.. the deck turns on but still no sound what could be the problem??