Switch matrix row test at 2J3 with Leon's code

Steps

• Ground 2J3 pin 9 (row 1) and put the tester LED (plain lead on +5 V) on IC11 pin 2; it should blink.
• Ground 2J3 pin 8 and check IC11 pin 3.
• Keep moving the ground down one 2J3 pin and the probe up one IC11 pin.
• Any step that does not blink points to a bad IC11 PIA.

Systems

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

Related tips

• Leon test: switch row inputs (2J3)
• Logic-probe the switch matrix
• Switch matrix connector pins and their chips
• Test the switch PIA IC11 with the Leon test EPROM
• Leon test: switch column drives (2J2)
• Driver board switch matrix resistors R204-R211
• Lamp matrix row test at 2J7 with Leon's code
• Whole game dead after working on a flipper EOS switch

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