Lamp matrix column test at 2J5 with Leon's code

Steps

• Clip +5 V (TP9 on System 6/7, or interboard pin 1) to any pin of 2J4 in place of the normal 18 V.
• With the playfield connectors on 2J5 and 2J7, touch each 2J5 pin with the tester LED; each should blink.
• On the bench without the playfield, probe instead the left leg of each small pre-driver along the right edge (even numbers Q62 through Q76).
• If the signal is missing while IC10 is good, check the 7408 inputs at IC13/IC14 (input pairs 1 and 2, 4 and 5, 9 and 10, 12 and 13) and outputs (pins 3, 6, 8, 11). Input present but no output: bad chip. No input: suspect a TIP42 (Q63-Q77 odd) or its pre-driver (Q62-Q76 even).

Systems

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

Related tips

• Diode-test the lamp column and row transistors
• Test a TIP42 lamp column transistor with a meter
• Background sound never stops at game over: sound-line driver chip
• Kicker coil locks on again after a new TIP122: dead 7408 gate on the driver board
• Damage after the black and white plugs were swapped
• Test each lamp column driver with a test lamp
• Lamp column still dead after a new TIP42
• How the CPU-controlled lamp matrix is wired

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