My daughter was fooling with the radio trying to play a DVD. Afterwards there is no sound coming from any of the speakers in the truck. The amp is a Precision Power A1200/4 channel. I checked all of the settings on the radio and it doesn't seem to be the problem. The sub pumps, but no basss comes out and there is a scratching type sound coming from the rear speakers. The light on the amp itself is red. I :think" it's supposed to be blue or green. Any input would be greatly appreciated. Even if it's a place I can start troubleshooting. Thanks