Memory protect chips to check after the 5101
On System 6 the memory protect circuit uses IC27 (4071) and IC12 (7808); on System 7 it is IC10 (4071) and IC12. They rarely fail. System 3/4 has no real memory protect, but a failed IC12 can still cause constant audit-mode starts.
Systems
Related tips
- Game always powers up in audit mode: bad 5101 memory chip
- Remove an old chip socket
- Chips that commonly fail on System 3-7 boards
- Which RAM chips go at IC13 and IC16
- Obsolete chips on System 3 to 7 CPU boards
- Leon's memory test results (versions from 11/01/03)
- Ignore the SW1 memory test unless the board has booted
- CPU chips Leon's test code does not need
Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part One, Clay Harrell (pinrepair.com)