All lamps in one row or column never light, or stay on.

A whole lamp row or column dead or stuck on

Cause: Usually the driver board: cracked header pin joints on 2J4, 2J5, 2J6 or 2J7, then the column or row transistors (column transistors fail more often).

Checks

• Resolder the lamp connector header pins.
• Diode-test the column TIP42s and row 2N6122s and their pre-drivers.

Fix

• Replace the failed transistors or chips.

Systems

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

Related tips

• Light a lamp row by grounding its transistor
• Logic-probe the lamp columns and rows
• Lamp rows stuck on: the 7406 at IC19
• Tester LED check of the lamp columns
• Tester LED check of the lamp rows
• MOSFET lamp column upgrade
• Lamp matrix column test at 2J5 with Leon's code
• Lamp matrix row test at 2J7 with Leon's code

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