BUX84 as a substitute for the 2N3584 HV transistor

Where the TO-66 2N3584 cannot be found, a TO-220 BUX84 can be used. Its tab is the collector and bolts to the board, so cut off its centre lead; enlarge the heat sink hole for the base and emitter if needed, and insulate the tab from the heat sink with a nylon washer and heat-shrink over the bolt.

Systems

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

Related tips

• The solenoid driver board also carries the 190 V display supply
• Capacitor C26 holds the display high voltage after power-off
• Set the display high voltage to about 170 V
• Displays burning too bright: HV regulator failed shorted
• No score displays light at all
• Rebuild the solenoid driver board high-voltage section
• First checks before repairing Bally score displays
• All score displays blank with the MPU fully booting

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