After replacing the HV parts, TP2 still cannot be set into the 155-190 V range.

High voltage still too high or too low after a rebuild

Cause: The C26 filter capacitor (160 uF, 350 V) is worn out.

Checks

• Recheck all new parts, then suspect C26.

Fix

• Replace C26 with a 160 uF 350 V capacitor.

The solenoid driver / regulator board makes about 190 V DC for the score displays (around 230 V on some Stern boards); a shock from it hurts. Work with the game unplugged and let the filter capacitors discharge, and use one hand and insulated probes for live checks.

Systems

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

Related tips

• Set the display high voltage to about 170 V
• Power up and set a rebuilt high-voltage section
• Capacitor C26 holds the display high voltage after power-off
• Where the display high voltage enters and leaves the solenoid driver board
• Displays burning too bright: HV regulator failed shorted
• All displays dark after fitting a new power supply: blown solenoid driver board fuse
• The solenoid driver board also carries the 190 V display supply
• No score displays light at all

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