MPU switch connector pins J2 and J3
Columns (strobes) 0-4 are J2 pins 1-5 (column 5, rarely used, is J4 pin 5). Rows (returns) 0-7 are J2 pins 8-15, and the same rows appear on J3 pins 9-16. J2 carries the whole matrix; J3 is used just for the cabinet switches: coin, credit, test, tilt and slam.
Systems
Related tips
- Switch reads closed even with switch connectors unplugged: shorted resistor on the MPU
- Rollover switch only registers with two diodes fitted: failing PIA at U10
- Switch matrix confused by a bad MPU DIP switch diode
- Bally switch matrix: 5 strobes by 8 returns, numbered 1 to 40
- One drop target only registers if it is the first one down: reseat and clean the PIAs
- Odd switch problems from corrosion at the DIP switches
- Telling a -17 MPU from a -35 by connector J5
- Coin door switch shorted to ground causes lamp and other odd faults
Source: Repairing Bally Electronic Pinball Games from 1977 to 1985, Part Three, Clay Harrell (pinrepair.com)