One to four switches that share a row or column do not work.

A few switches in a row or column all dead

Cause: The daisy-chained row or column wire has broken upstream, cutting off every switch after the break.

Checks

• Follow the wire from switch to switch and find where it stops.

Fix

• Resolder or replace the broken link.

Systems

• Williams System 3
• Williams System 4
• Williams System 6 / 6A
• Williams System 7

Related tips

• Switch column or row fault on the driver board
• Column 1 switches and switch wire colours
• Row or column fault on the playfield
• Leon test: switch column drives (2J2)
• Leon test: switch row inputs (2J3)
• Switch matrix column test at 2J2 with Leon's code
• Switch matrix row test at 2J3 with Leon's code
• One switch closing lights up its whole row in switch test: bad column driver chip

Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part Three, Clay Harrell (pinrepair.com)