Leon test: switch column drives (2J2)

Steps

• With the Leon test EPROM running, connect the tester LED's plain lead to +5 V.
• Touch the resistor lead to each 2J2 pin: it should blink with the CPU board LEDs.
• If a pin is dead but IC11 is good, check IC17/IC18 (7406): inputs on pins 1, 5, 9, 13 and outputs on 2, 6, 8, 12. Inputs toggling with a dead output means a bad chip.

Systems

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

Related tips

• Switch matrix column test at 2J2 with Leon's code
• Switch matrix row test at 2J3 with Leon's code
• Switch column or row fault on the driver board
• Switches stuck on: board or playfield?
• Board or playfield? The switch test jumper method
• Logic-probe the switch matrix
• A ball resting on one switch stops others in its column
• Switch matrix connector pins and their chips

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