Rebuilding the solenoid driver board high-voltage section

Steps

• Replace the parts of the 190 V regulator section with the kit parts listed for each position.
• Fit C26, CR21 and VR1 the right way round; all three are polarised.
• Put a mica or thermal insulator between Q21 and its heat sink, then check with a meter that there is no continuity from the Q21 case to the sink.
• Fit the finned heat sink on Q23.
• All resistors are 1/4 W except R35 (1 W), R51 (1/2 W) and R56 (1/2 W).
• The fuse holder can be changed to take standard 3AG fuses.
• Power up and set the display voltage with the adjust pot (about 190 V at SDB TP2).

This section works at about 230 V DC and C26 holds a charge; switch off, unplug and let it discharge before touching it.

Systems

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

Related tips

• Rebuild the solenoid driver board high-voltage section
• Ground mod for high-voltage cap C26
• Display voltage too high: driver TP2 equals TP4
• Solenoid driver/regulator board test point voltages
• Solenoid driver/voltage regulator board test points
• Where the display high voltage enters and leaves the solenoid driver board
• Jumper TP1 to TP3 on the solenoid driver
• Solenoid driver board: how the MPU selects a coil

Source: Bally solenoid driver board high voltage section rebuild