Find what is blowing a fuse

Steps

• Replace the fuse once with the correct type and value. If it blows again, stop; never fit a bigger fuse.
• Look up which connectors the fuse feeds in the schematic (for example F105, the fuse for high-power coils, supplies the cabinet on J105, the backbox on J106, the playfield on J107 and possibly the Fliptronics board on J104).
• Unplug those connectors, fit a new fuse and power on. If it still blows, the fault is on the board, often a shorted bridge rectifier.
• If it holds, plug the connectors back one at a time; the one that blows the fuse leads to the faulty device.
• A coil fuse that only blows once a game starts usually means a shorted driver transistor.

Systems

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

Related tips

• Finding whether a blowing fuse is a board or wiring fault
• Which fault blows which driver board fuse (WPC-89/WPC-S)
• Fuse F116 keeps blowing
• WPC-95 changed to small slow-blow fuses
• Line fuse that blows only with the coin door closed
• F111, F112 or the line fuse keeps blowing
• WPC-95 line fuse
• Common fuse ratings to stock

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