The backbox bridges and can capacitor are not logic power
The pair of bridges mounted on the backbox wall make coil and lamp matrix power, and the big can capacitor smooths the lamp matrix supply alone. Logic power for the CPU does not pass through any of them.
Systems
Related tips
- Replace the +5/+12 V logic filter capacitor
- Backbox bridge rectifiers and their wires
- Power circuits in a System 3-7 game
- Test a bridge rectifier with a meter
- Loose wires on the backbox bridge rectifiers
- What the power supply board takes in and puts out
- Upgrade logic rectifier diodes D7 and D8
- Test the power supply with its outputs unplugged
Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part One, Clay Harrell (pinrepair.com)