Remove or bypass WPC-95 GI diodes D25 to D32

Steps

• Check the driver board: early WPC-95 boards have diodes at D25 to D32 (two four-diode bridges for the two non-triac backbox GI strings); from Scared Stiff they were replaced with zero-ohm links.
• Power off and remove the driver board.
• Either remove the eight diodes and fit zero-ohm resistors or 18 gauge wire links, or
• keep the diodes and on the solder side jumper J103 pin 11 to J105 pin 5 and J103 pin 12 to J105 pin 6 with 18 gauge wire, or
• remove the diodes and fit four wire jumpers on the component side.
• Inspect for heat damage around the diodes and repair any scorched traces.

Systems

• WPC-95

Games

• Scared Stiff

Related tips

• A whole string of backbox lamps is out: blown GI fuse F110
• How the WPC lamp matrix works
• BR1 (D11-D14 on WPC-95) and the board around it scorched
• Lamp matrix fuse F114 (F106 on WPC-95) keeps blowing
• 12 V unregulated LED out on the driver board: open track to C8
• Flasher glows full bright until the bulb blows: shorted driver transistor
• No insert lamps at all, lamp supply fine: broken trace under a driver board capacitor
• An entire lamp row or column is out

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