Where to clip a bench supply onto the MPU

Connect +5 V to TP5 (beside the battery), ground to TP4 (at the end of the board away from the battery, next to TP1) and +12 V to TP2 (battery side, next to TP3). TP3 is the +21.5 V zero-crossing input and gets no lead from a PC supply.

Systems

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

Related tips

• Using a PC power supply as an MPU bench supply: which wires
• How the MPU sees the 43 V solenoid supply
• Double-check bench leads: a +12 V to +5 V short kills the MPU chips
• Testing an MPU in the game with only J4 connected
• MPU board test points
• MPU board test point voltages
• Why the MPU has ROM jumpers
• Telling a -133 MPU from a -35 or -17

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