A memory back-up capacitor instead of batteries

A 1 farad memory capacitor charges while the game is on and keeps the RAM alive when off, and it never leaks. The game needs several hours on to charge it first, then about an hour a month to keep it charged.

Systems

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

Related tips

• Memory cap or battery does not keep scores

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