Eight switch matrix fault patterns and what they mean
Column shorted to ground: closing any switch in it shows that switch's whole row closed. Row shorted to ground at a diode's non-banded end, or at its banded end: the whole row shows closed all the time. Two columns shorted together: a closed switch also shows the same row in the other column. Two rows shorted: a closed switch also shows the same column in the other row. A column shorted to a row: only the switch at their crossing shows closed, falsely. Open switch diode: only that switch is dead. Shorted switch diode: false readings only when other switches in its row or column close too. For ground shorts, break the daisy chain from its far end one switch at a time until the fault clears. Most faults show up as row failures.
Systems
Related tips
- Narrowing a switch matrix fault to the CPU board, wiring or opto boards
- How the switch matrix reads a switch
- How the Williams switch matrix is scanned
- Use the switch matrix table in the manual
- Matrix fault remains with a good CPU board
- WPC switch matrix basics
- Switch matrix chips on the CPU board
- Switch matrix wire colors (all WPC games)
Source: Repairing Williams/Bally WPC Pinball Games from 1990 to 1999, Part Two, Clay Harrell (pinrepair.com)