Late System 7 CPU boards lack LEDs and DIP switches

Later System 7 CPU boards were built without the two diagnostic LEDs, switch SW2 and the two DIP switch banks; these can be fitted to make the board backward compatible.

Systems

• Williams System 7

Related tips

• CPU DIP switches: used by System 3, ignored from System 4 on
• Add two test LEDs to a System 7 CPU board
• System 7 CPU LEDs are swapped versus System 6
• Is it the CPU board or the driver board? Boot the CPU alone
• Identifying a System 3 to 7 CPU board
• System 7 CPU board test points
• A System 7 CPU board can run any System 3 to 7 game
• CPU LEDs flash once, then come back on and stay on

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