WPC coils need no diode except the flippers

The kickback diode for each coil lives on the power driver board, so playfield coils do not need one on the coil. Flipper coils are the exception and must keep their diodes.

Systems

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

Related tips

• Why WPC coil diodes are on the driver board
• Grounding test for WPC coils 1-8
• Firing each coil from the WPC solenoid test
• The four groups of WPC coil outputs
• Coil-not-working checklist
• No 50 V coils work
• Checking the coil supply at TP6
• WPC solenoid driver groups

Source: Pinball Machines: How They Work & Troubleshooting, Norbert Snicer