Changing the CPU batteries without losing settings

Steps

• Open the backbox to reach the CPU board and turn the game on.
• Note the battery orientation: positive end up on all WPC boards except WPC-S, where positive faces right.
• Remove the old batteries and check the holder contacts; clean light corrosion with 220 grit paper, or turn the game off and replace a damaged holder.
• Write the date on the new batteries and fit them with the game still on, so the settings are kept.
• Turn the game off and measure across the holder: black lead on the lower-left solder point (upper-left on WPC-S), red on the upper-right (lower-right on WPC-S). Expect about 4.5 to 4.8 V DC.
• Check U8 pin 28 against ground with the game off: at least 4 V.

Systems

• WPC Alpha-Numeric
• WPC Dot Matrix
• WPC Fliptronics
• WPC DCS
• WPC-Security (WPC-S)
• WPC-95

Related tips

• Changing batteries without losing settings
• Batteries get hot with the game on
• Battery power not reaching the RAM: diode D2
• The batteries also power the U9 ASIC clock
• Cleaning up alkaline battery leakage on a CPU board
• New batteries die in weeks or settings still lost: U8 RAM
• "Factory Settings Restored" every power-on
• Fitting a remote battery holder to a WPC CPU board

Source: Repairing Williams/Bally WPC Pinball Games from 1990 to 1999, Part Three, Clay Harrell (pinrepair.com)