Bally switch matrix: 5 strobes by 8 returns, numbered 1 to 40
Bally uses five strobes (columns ST0-ST4) and eight returns (rows), 40 switches on 13 wires. Numbering starts at switch 1 for column 0, row 0, so column 0 holds switches 1-8, column 1 holds 9-16 and so on. Switches that look missing from the schematic are usually the cabinet ones (tilt, slam, credit, coin and test).
Systems
Related tips
- Odd switch problems from corrosion at the DIP switches
- Switch matrix confused by a bad MPU DIP switch diode
- MPU switch connector pins J2 and J3
- Prove the MPU switch inputs with the harness unplugged
- Switch reads closed even with switch connectors unplugged: shorted resistor on the MPU
- Coin door switch shorted to ground causes lamp and other odd faults
- Rollover switch only registers with two diodes fitted: failing PIA at U10
- One drop target only registers if it is the first one down: reseat and clean the PIAs
Source: Repairing Bally Electronic Pinball Games from 1977 to 1985, Part Three, Clay Harrell (pinrepair.com)