A whole switch column or row is dead or stuck closed, and the jumper test shows the board is at fault.

Switch column or row fault on the driver board

Cause: Column (drive) faults: IC17/IC18 (7406), which fail more often. Row (input) faults: IC15/IC16 (4049). Otherwise the IC11 PIA.

Checks

• Logic-probe or LED-test the chips (see the related procedures).

Fix

• Replace the failed chip; socket it.

Systems

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

Related tips

• Switches stuck on: board or playfield?
• Whole game dead after working on a flipper EOS switch
• System 6: game stuck in tilt with switch 1 closed: cracked pins in the 2J2 plug
• Board or playfield? The switch test jumper method
• Leon test: switch column drives (2J2)
• Leon test: switch row inputs (2J3)
• Driver board switch matrix resistors R204-R211
• Switches missed in a System 7 game with an older driver board

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