Repairing battery corrosion on the CPU board

Steps

• Remove the corroded parts and sockets: the 6808/6802 CPU socket at 3D (40 pin), the RAM socket at 5D (28 or 24 pin) and both EPROM sockets (5B, 5C).
• Scrub the area with equal parts white vinegar and water to neutralise the corrosion.
• Rinse with clean water and let the board air-dry completely.
• Sand any grey, corroded copper back to bright metal.
• Check every trace through the area for continuity; breaks are often invisible.
• Fit new sockets and refit the chips.

Battery electrolyte is corrosive; wear gloves and eye protection when cleaning it off.

Systems

• Data East CPU Version 1/2
• Data East CPU Version 3
• Data East/Sega CPU Version 3b

Related tips

• Repair battery corrosion on the CPU board
• Replacement battery holder for the CPU board
• Battery orientation on Data East and Sega CPU boards
• Check that battery power reaches the RAM at 5D
• Fit a remote battery holder
• Change the CPU backup batteries yearly, with the game on
• "Memory Error, Open Door" or "open the coin door" at power-on
• New batteries but still a memory error: check D25

Source: Repairing DataEast 1987 (Laser War) to Sega 1995 (Batman Forever), Part Two, Clay Harrell (pinrepair.com)