94 Accord Stereo problem
 

My son has a 94 Accord with a Pioneer DEH-16 stereo. It was working great then one day he went out to his car and the stereo wouldn't power on. I checked all fuses in the fuse box and the one on the back of the stereo and all were fine. I also looked over all the wires on the harness and they all appeared intact. Whats the next step? What could the problem be? Any help is appreciated.