After a coil change the flipper fuse blows, and the flipper may lock on at power-up or game start.

Fliptronics flipper coil wired wrongly

Cause: Reversed or misplaced wires on a Fliptronics flipper coil route the hold circuit through the heavy winding, damaging the coil diodes, the Fliptronics drivers and the hold traces.

Checks

• Turn the game off and compare the wiring to the usual colors.
• Check every 1N4004 diode for that flipper on the Fliptronics board.
• Test the TIP36 power driver and the hold TIP102 and 2N4403.
• Look at the solder-side traces from connector J902 for burnt-off hold traces.

Fix

• Rewire the coil correctly.
• Replace both 1N4004 diodes on the coil and the blown fuse.
• Replace any failed transistors and repair burnt traces.

Systems

• WPC Fliptronics
• WPC DCS
• WPC-Security (WPC-S)
• WPC-95

Related tips

• Flipper energizes and stays up at power-on or game start
• Fliptronics: flipper will not hold up (flutters)
• Fliptronics II board components
• How Fliptronic flipper drive works
• A coil or flasher energizes as soon as the game is turned on
• STNG: diverter coils lock on during play
• STNG: under-playfield diverter coils lock on during play
• Flipper stuck up with power on (Playboy and later)

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