Cleaning up battery leakage on the CPU board

Steps

• Remove the battery holder and any corroded chips and sockets near it.
• Wash the area with a 50/50 mix of water and white vinegar to neutralise the alkaline residue, then rinse with water and dry.
• Sand corroded areas back to bare copper.
• Replace the holder, sockets and parts; unwashed corrosion comes back.
• Mount the batteries off the board from now on.

Leaked battery residue is caustic; wear gloves and eye protection.

Systems

• Williams System 11
• Williams System 11A
• Williams System 11B
• Williams System 11C

Related tips

• Fitting a remote battery holder
• Changing the CPU batteries without losing settings
• 'ADJUST FAILURE' every time it powers on: battery corrosion on the CPU board
• New CPU batteries go flat quickly
• "Factory Setting" or "Adjustment Failure" at power-on
• "Factory Setting" or "Adjustment Error" at power-on
• Settings lost although the batteries are good (blocking diode D2)
• A shorted D2 tries to charge the batteries

Source: Repairing Williams System 11 Pinball 1986 to 1990, Part Three, Clay Harrell