I'd check the high voltage power supply for the DMD. Rarely does a DMD die and not show at least some flickering. It could also be a bad ribbon cable and or the DMD controller not running. Up until the SAM system, all Data East/Sega/Stern games use a DMD controller that is it's own CPU and interacts with the MPU through a ribbon cable. If the game is rebooted and the DMD shows its software version, but then goes blank, the high voltage power supply certainly is working. Also, a lack of 12v can cause certain brands of DMDs not to light up. Since you say there is no sound, either the volume is turned down, the speakers are unplugged, or there is a problem with the audio amp circuit.