A game that seemed to run fine starts misbehaving and eventually stops working properly, with leaked battery residue around the CPU board's battery holder.

Game faults after the CPU battery leaked: corrosion ate traces and chips

Cause: The on-board batteries leaked (lithium cells can leak too). Over time the electrolyte ate into traces and damaged the chips near the holder, including the EPROM and the PAL that decodes the memory map.

Checks

• Remove the batteries straight away on any older game and inspect the board around the holder on both sides for green or white residue.
• Trace the signals that run through the corroded area; this system addresses memory and I/O through a PAL chip rather than PIA chips and has no LED repair codes, so a schematic is needed.

Fix

• Neutralise the residue (the poster used vinegar), then clean with board cleaner and polish the pads bright.
• Fit machine-pin sockets and replace every chip in the corroded zone (eight in this case, including the EPROM).
• Repair broken traces with jumper wire.
• Fit NVRAM or a remote battery holder so it cannot happen again.

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

Systems

• Sega/Stern Whitestar

Games

• The Sopranos

Related tips

• Game keeps resetting with blank display and blinking lamps: faulty 6264 RAM
• Won't boot after a board swap, CPU LEDs dark: loose 5 V wire in the CPU power plug

Source: Pinball Repair help group!! (Facebook group)