Solenoid driver board: how the MPU selects a coil

The MPU sends a 4-bit binary solenoid number on lines A (1), B (2), C (4) and D (8) plus a bank select line to the solenoid decoder on the SDB. The decoder drives three groups of driver transistors: solenoids 1-7, 8-14 and 15-19.

Systems

• Bally MPU AS-2518-17
• Bally MPU AS-2518-35
• Stern MPU-100
• Stern MPU-200

Related tips

• Solenoid driver/regulator board test point voltages
• Jumper TP1 to TP3 on the solenoid driver
• Solenoid driver/voltage regulator board test points
• Ground mod for the solenoid return at J3 pins 23-24
• Skip the driver board mods on Baby Pac-Man
• Adding a ground jumper at C23
• MPU locks with LED on because of C23 or Q20 on the solenoid driver board
• Rebuilding the solenoid driver board high-voltage section

Source: Bally - Stern Solenoid Driver Troubleshoot Aid