Lamp matrix row test at 2J7 with Leon's code

Steps

• Clip +5 V to any pin of 2J4 and ground any pin of 2J6 (or leave the game connector on 2J6).
• Probe each pin of 2J7 with the tester LED; each should blink.
• If a pin is missing the signal while IC10 is good, check the 7406 outputs: IC19 pins 2, 4, 6, 8, 10, 12 and IC12 pins 2 and 4. No output: bad chip.
• Output good: suspect the 2N5060, 2N6427 or 2N6122 on that row.

Systems

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

Related tips

• Lamp rows stuck on: the 7406 at IC19
• Switch matrix column test at 2J2 with Leon's code
• Switch matrix connector pins and their chips
• Damage after the black and white plugs were swapped
• Lamp row still dead after a new TIP122
• How the lamp matrix runs 6.3 V bulbs on 18 V
• Tester LED check of the lamp rows
• Diode-test the lamp column and row transistors

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