Where the 43 V coil supply goes

Supply J1-6 feeds the playfield flipper coils; J3-9 the flipper relay on the solenoid driver; J3-12 MPU J4-15; J3-13 the backbox knocker where fitted. J3-19 and J3-20 are the solenoid returns from driver J3-23 and J3-24. Driver J3-5 goes to sound board J1-9 on many games.

Systems

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

Related tips

• Check the wire from a coil back to the solenoid driver board
• One coil dead with a good transistor and power at the coil

Source: Repairing Bally Electronic Pinball Games from 1977 to 1985, Part One, Clay Harrell (pinrepair.com)