Testing a resistor network with a meter
Steps
- Bussed network: find pin 1 (white square on the board, dot on the part). Put one ohmmeter lead on pin 1 and touch each other pin in turn; every pin should read the same value.
- Isolated network: measure the two end pins as a pair, then step both leads along two pins at a time; each pair should read the same.
- In circuit some pins read differently (pin 10 of SR17 reads about half); out of circuit every pin should match.
- An in-circuit test can pass a bad part, so replace any network that reads oddly.
Systems
Related tips
- Replacing SRC6 with a plain bussed resistor network
- Bussed versus isolated resistor networks on the CPU board
- Random switch closures, random tilts or slam from bad resistor networks
- Random slam tilts: replace the SRC6 resistor pack on the CPU board
- Lane change and shooter lane switches don't register: failed column driver Q42
- Playfield switches fire coils and switch columns misread: failed column driver Q44
- Every switch shows active, even with the switch plugs removed: failed PIA at U38
- Inlane, outlane and drain switches all dead: blown switch transistor Q49
Source: Repairing Williams System 11 Pinball 1986 to 1990, Part Three, Clay Harrell