Cut the original MPU battery off right away

Every 1977-1985 Bally MPU has a rechargeable nicad soldered on, which the board overcharges until it leaks. Cut it off and discard it. The game runs without it; only scores, audits and on some games settings such as the sound option are lost at power-off.

Battery leakage is caustic; wear gloves and eye protection while cleaning it off.

Systems

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

Related tips

• Repairing battery corrosion on the MPU
• Bally-35 MPU: remove the on-board rechargeable battery before it leaks
• Repair battery corrosion before chasing MPU flash codes
• Fitting a remote AA battery pack
• Reset section parts typically ruined by battery corrosion
• Memory cap or battery does not keep scores
• Knocker fires 'randomly' in play: no memory battery, so every game sets replays
• Switch faults from corrosion under MPU J2 or J3

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