Resets when the flippers are used.

Resets from damaged flipper coil diodes

Cause: Each flipper coil carries two diodes on the coil itself; if they are cracked, broken or missing the game can reset. Less common on WPC than on earlier systems.

Checks

• Inspect both diodes on each flipper coil for cracks or broken leads.

Fix

• Replace any doubtful flipper coil diodes with 1N4004s, fitted the right way round.

Systems

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

Related tips

• Testing the diodes on a flipper coil
• Fliptronics flipper coil wired wrongly
• Testing a coil, switch or flipper diode with a meter
• Fliptronics: flipper will not hold up (flutters)
• Testing a coil diode
• Testing the diode on a coil
• Which way a coil diode goes
• Which way a coil diode goes

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