Replacing the CPU battery with a remote AA pack
Steps
- Desolder and discard the original rechargeable DataSentry or AA NiCad (3.6 V) from the CPU board.
- Mount a three-AA holder off the board.
- Put a 1N4004 or 1N5817 in the red lead: band toward the board "+" pad, other end to the pack positive, so the charger cannot charge the alkalines.
- With the pack fitted, measure 5101 RAM pin 22 (top right pin of the chip three to the right of the game PROM) to ground: expect 4.1 to 4.5 V DC.
Battery leakage is caustic potassium hydroxide; wear gloves and eye protection when cleaning a corroded board.
Systems
Related tips
- Fit a remote AA battery pack to a System 80 CPU board
- Early driver boards lack isolation diodes
- Clamp diode mod to protect U5
- Fitting a remote battery holder to a WPC CPU board
- Fitting a remote battery holder
- Repairing battery corrosion on the CPU board
- Move the CPU batteries off the board
- Switch row (return) circuit on the CPU board
Source: Gottlieb System 1 Pinball Repair from 1977 to 1980, Clay Harrell (pinrepair.com)