Scores and settings are lost after the game sits off for a while.

Memory cap or battery does not keep scores

Cause: Blocking diode CR5 leaking, R12 open or high, the RAM type, or a broken trace from the battery pad to U8.

Checks

• With the game off, DC should be on only one side of CR5 (1N4148).
• Measure R12; it should be 270 ohms.
• With the game off, measure U8 pin 22 to ground: 4 to 4.6 V is expected.

Fix

• Replace CR5 or R12 as needed.
• Repair the trace from the battery pad to the 5101, which runs through the corrosion zone.
• Some 5101s hold memory longer than others on a cap (PCD5101P works well).

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
• Fitting a remote AA battery pack
• Cut the original MPU battery off right away
• Bally-35 MPU: remove the on-board rechargeable battery before it leaks
• Reset section parts typically ruined by battery corrosion
• Repair battery corrosion before chasing MPU flash codes
• Knocker fires 'randomly' in play: no memory battery, so every game sets replays
• Corrosion under MPU J4 can destroy every chip

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