Power a 6803 CPU board on the bench with a PC supply

Steps

• Use an old PC power supply (an AT type has a real power switch). An ATX supply only turns on if the green PS-ON wire, pin 14, is joined to a black ground wire.
• Take power from a 4-pin drive plug: red is +5 V, yellow +12 V, black ground.
• Jumper the CPU board for 27128 EPROMs: fit W2, W4 and W6, and leave W1, W3 and W5 open.
• Connect +5 V to J1 pins 10-12 (TP1), ground to J1 pins 7-9 (TP2) and J4 pins 5-6, and +12 V to J1 pin 6 (TP3). J1 is at the lower right, J4 at the upper left.
• Double-check every lead before switching on.

A slip that joins +12 V to +5 V can destroy every chip on the board; check the leads before power-up.

Systems

• Bally 6803

Related tips

• What is on the 6803 CPU board
• Test EPROM fitted but the LED does not blink
• Check the 6803 clock at U1 pins 2 and 3
• CPU board test points
• Factory CPU jumpers by game
• Find a bad 6803 or a shorted bus line
• Electronic spares for 6803 board repair
• Cybernaut can have a -35, 6802 or 6803 boardset

Source: Repairing Bally 6803 Pinball Games from 1985 to 1989, Clay Harrell (pinrepair.com)