Backbox bridge rectifiers and their wires
Two 35 A bridges below the power supply board: 6BR1 with blue wires takes 13.5 VAC for the lamp matrix, 6BR2 with red (green on some System 3/4) wires takes 25.5 VAC for the coils. System 7 adds bridge BR1 on the power supply board for the 9.3 VAC that becomes +12 and +5 V.
Systems
Related tips
- Test a bridge rectifier with a meter
- Loose wires on the backbox bridge rectifiers
- The backbox bridges and can capacitor are not logic power
- Upgrade logic rectifier diodes D7 and D8
- Flippers too weak for the top lock: loose, arcing bridge rectifier connections
Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part One, Clay Harrell (pinrepair.com)