After a flipper rebuild with new mechs, one flipper does nothing when the button is pressed, the lights dim, and the flipper supply fuse eventually blows.

New flipper coil dead and blowing the flipper fuse: shorted diode on the new coil

Cause: The diode on the brand-new coil had been damaged, most likely during the install (a wiring mistake had already blown the fuse once). A shorted coil diode makes the coil look bad and pulls the supply down.

Checks

• Confirm the power wire goes to the banded side of the coil diode.
• Lift one leg of the diode and test it on its own; a diode tested in circuit can read fine.
• Swap the old coil back in: if it works, the new coil's diode or the coil itself is the fault.

Fix

• Replace the diode on the new coil (or fit the old coil back if it was good), then retest with the correct fuse.

Systems

• Williams System 9

Games

• Sorcerer

Related tips

• Williams 50 V fat flipper coils ranked by strength

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