Driver board TP2 reads well over 190 V, close to the 230 V at TP4.

Display voltage too high: driver TP2 equals TP4

Cause: The high-voltage regulator section of the solenoid driver board has failed.

Checks

• With the HV fuse out, compare TP2 and TP4 to ground.

Fix

• Repair the HV section before reinstalling the HV fuse, or the displays can be damaged.

The score display supply runs at 170-230 V DC; keep hands off the rectifier and driver boards with power on.

Systems

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

Related tips

• Rebuilding the solenoid driver board high-voltage section
• High-voltage section parts on the solenoid driver board
• Ground mod for high-voltage cap C26
• Solenoid driver/regulator board test point voltages
• Solenoid driver/voltage regulator board test points
• Solenoid driver TP1 below 5 V with TP5 normal
• Logic 5 V reads over 5.25 V on Bally/Stern: the R49 boost resistor
• F2 blown, no display high voltage at TP2

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