During solenoid test the center eject (solenoid 4) does nothing, and from then on the solenoid fuse blows as soon as the game is switched on.

Center eject dead and solenoid fuse blows at power-up: shorted coil and drive transistor

Cause: The center eject coil had shorted (almost no resistance) and took out its drive transistor Q24 on the MPU board, which then held the circuit on. In-circuit checks made several neighbouring drivers (Q33, Q25, Q32) look shorted too, but out of circuit only Q24 was bad.

Checks

• Measure the coil's resistance; a reading near zero means a shorted coil.
• Pull the MPU and test the suspect drive transistors out of circuit; in-circuit readings can mislead because the drivers share paths.
• If the transistor tests good, check the logic chip feeding it (here U20, a 7408) against a known-good identical chip on the same board with the meter on diode test.

Fix

• Replace the shorted drive transistor (here Q24).
• Disconnect the bad coil and power up to confirm the fuse holds, then fit a new coil.
• Many techs replace both drive transistors for that solenoid at the same time to avoid a repeat failure.

Systems

• Williams System 11

Games

• Road Kings

Related tips

• Special solenoids dead after fitting an early System 11 CPU in a later game
• Flash lamps stay lit after fitting LED flashers: System 11 warming resistors
• A-bank coil not working
• Whole groups of coils or all flashers dead: A/C select relay stuck
• A solenoid does not fire in the diagnostic test
• C-bank coil or flasher not working
• Sling or bumper locks on at power-up (System 11)
• Checking for power at a coil

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