Stupid question, but I'm guessing you've pressed the power button? Can you hear the hardware inside turning on? Have you taken it apart and checked to see if the solder on the wires came loose?
I used to tear older consoles apart and repair them in high school and I loved seeing how they operated, but it always made me wonder what people did to their consoles to break them so often. All of my original consoles (even original NES and Atari systems) are in perfect working condition.