Replacing filter cap C23

Steps

• Pick a 10,000 to 15,000 uF cap rated 20 V or more (12,000 uF for two-flipper games, 15,000 uF for more flippers). Going much bigger strains the bridge at switch-on; never go lower.
• Mount it flat on the board like the original, held with nylon ties.
• Connect it to the board pads with short jumper wires rather than soldering a radial cap straight in, so vibration cannot crack the joints.
• Write the date on the new cap.
• Repeat the ripple and +5 V checks.

Systems

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

Related tips

• Replace filter cap C23 on every game
• MPU locks with LED on because of C23 or Q20 on the solenoid driver board
• Solenoid driver TP5 under 13 V
• Solenoid driver TP1 below 5 V with TP5 normal
• Only about 1.6 V at solenoid driver TP1
• Route of the +12 V supply to the MPU and 5 V regulator
• Logic 5 V reads over 5.25 V on Bally/Stern: the R49 boost resistor
• Ground mod for high-voltage cap C26

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