Quoted from cyroute:
It seems all the wire colors I have found that should have 5v are Blue/Gray stripe. The reason I thought the display was in play because it has a Blue/Gray with 5v going in but the other Blue/Gray on the other connector on the display doesnt have 5v its low like the the opto blue/gray and the pop bumper blue/gray wires.
From the manual it says the 5V wires are 688 blue with two gray stripes. Schematic show from the power supply pins 1 and 2 go to the MPU. Pin 3 to display. Pin 4 to sound card. Looks like the wire on pin 6 may go to the playfield and may be the one supplying the pop bumper boards and the opto board.
Can you follow those wires to see if one is cut or broken off?