Raising the WPC/WPC-S +5 V to about 5.15 V (last-resort reset fix)

Steps

• Use this only after everything else for resets has been done. The LM323K is in spec anywhere from 4.7 to 5.3 V, but WPC resets below about 4.9 V.
• The LM323K metal case is normally grounded through its mounting bolt. Cut the ground trace around the bolt on the solder side; some board revisions also have a component-side ground trace to cut.
• Connect the bolt to ground through a 22 ohm 1/2 W resistor; this lifts the output to about 5.15 V (33 ohms gives about 5.25 V).
• Buzz the regulator case to ground with the meter to confirm it is isolated apart from the resistor.

Systems

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

Related tips

• What a WPC game reset is
• Pre-WPC-95 resets: replace BR2, C5, C4 and the J101 pins together
• Watching the supplies while the game resets
• Resets: +5 V at the driver board test point is low
• Resets remain after rectifiers, caps and connectors are done
• Resets and GI that will not dim after BR2 was replaced
• Resets continue although the bridge and diodes test good
• Resets or dead banks of coils or lamps from cracked bridge or cap solder

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