A single coil does nothing in game or test.

One coil will not fire

Cause: Its TIP36 and/or TIP102 driver or pre-driver transistor, a broken coil wire, missing +50 V at the coil, or rarely the 74LS374 latch.

Checks

• Measure +50 V from the coil's power lug to ground.
• Check the coil wires.
• With power on, briefly ground the driver TIP102 tab: if the coil fires, the transistor or its pre-driver may be bad.

Fix

• Repair wiring, or replace the driver and pre-driver transistors.

Systems

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

Related tips

• One coil does nothing in the solenoid test
• No 50 V coils work
• A coil does nothing although its fuse is good
• A solenoid will not fire in the solenoid test
• Two or more coils fire together
• Coil-not-working checklist
• Grounding test for WPC coils 1-8
• Checking the coil supply at TP6

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