Switch matrix column test at 2J2 with Leon's code

Steps

• Tester LED plain lead to +5 V.
• Touch each pin of driver connector 2J2; the LED should blink in time with the CPU LEDs.
• A pin missing the signal with good IC11 outputs means a failed 7406 at IC17 or IC18.
• Compare the 7406 inputs (pins 1, 5, 9, 13) with outputs (pins 2, 6, 8, 12): input blinking but output not means that chip is bad.

Systems

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

Related tips

• Switch matrix connector pins and their chips
• Lamp matrix row test at 2J7 with Leon's code
• Damage after the black and white plugs were swapped
• Lamp rows stuck on: the 7406 at IC19
• One switch closing lights up its whole row in switch test: bad column driver chip
• Leon test: switch column drives (2J2)
• Logic-probe the switch matrix
• Lamp row still dead after a new TIP122

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