Flipper ROM colour tells you the system generation
The built-in test code lives in the two flipper ROMs at IC20 and IC17 on the CPU board. White flipper ROMs mean System 3, yellow System 4, green System 6 and blue System 7. System 3 (white) test mode is entered differently from System 4 to 7.
Systems
Related tips
- Which System 3 to 7 games use which flipper ROM system
- Flipper ROM color codes by system
- Flipper ROM colours: white, yellow, green and blue
- "Flipper ROMs" have nothing to do with the flippers
- System 3 CPU board ROM layout
- System 7 CPU ROM sockets
- System 4 CPU board changes and ROM layout
- System 6 CPU board changes and ROM layout
Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part Three, Clay Harrell (pinrepair.com)