CPU board test points

TP1 is +5 VDC, 4.9 to 5.2 V (J1 pins 10-12). TP2 is ground, also found on J1 pins 7-9 and on J4 pins 5-6. TP3 is unregulated 12 VDC, anywhere from 12 to 18 V (J1 pin 6). TP4 is battery voltage, 3.5 to 4.5 V, which the game does not need to boot.

Systems

• Bally 6803

Related tips

• What is on the 6803 CPU board
• Factory CPU jumpers by game
• Bench-test a CPU board with the 6803 test EPROM
• Power a 6803 CPU board on the bench with a PC supply
• CPU board landmarks: battery, LED, relay and ROMs
• CPU jumpers JW1-JW6 for game EPROM size
• Check the 6803 clock at U1 pins 2 and 3
• Test EPROM fitted but the LED does not blink

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