Controlled lamps do not light.

No lamp matrix voltage

Cause: Blown F3, a bad connector, a failed 6BR1 bridge or loose wires on it; rarely the 30,000 mfd 25 V backbox can capacitor.

Checks

• Black lead on J4 pin 1 (ground), red on J4 pins 5 to 8: expect 16 to 20 VDC.
• Check F3 and the wires on 6BR1.

Fix

• Replace the fuse, connector or bridge as found; tighten or solder the bridge wires.

Systems

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

Related tips

• All matrix lamps out, everything else works
• How the lamp matrix runs 6.3 V bulbs on 18 V
• Burnt GI plugs on the power supply board
• Burnt GI connectors on the power supply (System 7, Hot Tip, Lucky Seven)
• No general illumination: trace the 6.3 V AC
• GI in at the power supply but not out: check the GI relay
• Replacement GI relays
• GI lamps and matrix lamps

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