Bally assembly designators A1-A8
A1 is the display driver boards, A2 the power supply/rectifier board, A3 the solenoid driver/voltage regulator, A4 the MPU, A5 the lamp driver and A8 the sound board. Schematics and wiring tables use these names with the connector, for example A3 J3-12.
Systems
Related tips
Source: Repairing Bally Electronic Pinball Games from 1977 to 1985, Part One, Clay Harrell (pinrepair.com)