A coin-door test button, slam tilt or EOS switch does nothing in switch test, while the matrix may be fine.

A dedicated (direct) switch does not work

Cause: Dedicated switches bypass the ULN2803 and simply pull their orange row wire to the black ground wire; a broken ground wire is the usual cause. They enter through connector J205 and are read by the U16 and U17 LM339s plus the U15 74LS240 on the CPU board.

Checks

• In switch test, ground each pin of J205 in turn; if the input registers, the CPU board is fine and the wiring is at fault.

Fix

• Repair the ground or switch wiring, or replace U15/U16/U17.

Systems

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

Related tips

• "Slam tilt stuck closed" at power-on
• One switch does not work
• Testing CPU switch rows with the switch levels test
• Row or column "ground short" errors
• Optos test good but still don't work: the opto board
• Weak or dead flippers from failing LM339s on the Fliptronics board
• "Check Fuse F114/F115" (F106/F101 on WPC-95): step-by-step
• Fliptronics: flipper coil gets hot after a while of play

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