Run the System 3-6 built-in CPU test (SW1)

Steps

• The game must have booted to attract mode with game ROMs, flipper ROMs and the driver board in place.
• On System 6, open the coin door (memory protect switch).
• Press the CPU board diagnostic button SW1 (the lower of the two) once.
• Pass: both LEDs flash briefly twice and go out. The game stays out of attract mode until power is cycled.
• Repeat three or four times. Only trust results that are the same every time; varying results point first to IC19 (5101), then IC13/IC16 and their sockets.

Systems

• Williams System 3
• Williams System 4
• Williams System 6 / 6A

Related tips

• A System 7 CPU board can run any System 3 to 7 game
• Which CPU boards can run which system firmware
• Identifying a System 3 to 7 CPU board
• What changed on the System 6A CPU board
• System 6 CPU board test points
• System 6 CPU board jumpers J1 to J6
• System 3 CPU board ROM layout
• Obsolete chips on System 3 to 7 CPU boards

Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part Two, Clay Harrell (pinrepair.com)