The drop target reset coil is the only coil that does nothing in solenoid test, although its resistance at the lugs looks normal and power reaches the coil.

Drop target coil won't fire in test: replace its diode

Cause: The coil's diode was faulty (it read open both ways once one leg was lifted).

Checks

• Measure the coil at its lugs (the copper wire is coated, so probes on the bare winding read nothing).
• Lift one leg of the diode and test it with the meter's diode setting: it should conduct one way only.
• With power at one lug, briefly ground the other lug to see if the coil fires.

Fix

• Replace the coil diode, banded end to the power side, matching the original.

Systems

• Bally MPU AS-2518-35

Games

• Star Trek

Related tips

• LE: one coil fires another (outhole fires a memory coil): coil diodes
• Wrong coil fires or a coil never fires
• Drop target falls instead of the ball being kicked out (SEB games)
• Expander-driven coils fire in pairs: drop target coil fitted without its second diode
• Drop target coil fuse keeps blowing: shorted diode on the coil
• Check every coil's resistance before first power-up
• Use the solenoid test to find a coil that does not fire
• Check for power at a coil and fire it by hand

Source: Pinball Repair help group!! (Facebook group)