System 3-6 SW1 test results
Upper LED stays on: ROM read fault at IC14, IC17 or IC20 (in practice IC14, since the game would not boot with bad IC17/IC20). Lower LED on: 6810 RAM fault, check IC13, IC16, their sockets and IC8. Both on after flashing: 5101 at IC19 (also check IC12 and IC7), or the coin door was closed on System 6. Two flashes and off: RAM and ROM pass; remaining faults are likely the driver board, interconnector or display PIA IC18.
Systems
Related tips
- Identifying a System 3 to 7 CPU board
- What changed on the System 6A CPU board
- System 6 CPU board test points
- Which System 3 to 7 games use which flipper ROM system
- System 6 CPU board jumpers J1 to J6
- A System 7 CPU board can run any System 3 to 7 game
- Chips that commonly fail on System 3-7 boards
- System 3 CPU board ROM layout
Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part Two, Clay Harrell (pinrepair.com)