Some, but not all, switches in a row or column do not register.

Several switches in one row or column dead: a broken daisy-chain wire

Cause: The row and column wires run from switch to switch; a break upstream kills every switch after it. Wires can also fatigue and break inside the insulation at the CPU connector. If other switches in the same row and column work, the CPU board is probably fine.

Checks

• Check in the manual which switch comes first in the chain.
• Inspect the wire at each switch and at the CPU connector.

Fix

• Resolder or replace the broken wire.

Systems

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

Related tips

• Most of switch row 6 dead, last switch works: broken row wire
• Several switches in one row never register: broken row wire at another switch
• A whole switch row or column is dead
• Spinner stops registering: broken wire on an upper flipper EOS switch
• Row or column "ground short" errors
• WPC switch numbers give the column and row
• Tracing a column of dead switches from the manual chart
• Microswitch with a broken terminal tab: replace the switch, don't move the wire

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