After a new U20, work every flagged switch once

After replacing U20 the fuse holds but the test report lists many switches. Go to T.1 switch edges and close each listed switch by hand with a ball (the manual shows where they are), then leave diagnostics; or simply play a game.

Systems

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

Related tips

• Switch columns to U20 pins
• Clearing a switch flagged in the power-on test report
• A whole switch column dead or all closed
• A whole switch row dead or all closed
• Finding which switch is shorted to a power circuit (U20 socket probe)
• Using the switch edge test
• How the switch matrix reads a switch
• Why CPU U20 fails and how to replace it

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