Add fuses to the inputs of the backbox bridges

Steps

• Get two fuse holders, two 8 A slow-blow fuses and 18 gauge wire.
• Mount a holder next to 6BR1 (blue wires, lamp matrix) with a 1/4" sheet metal screw.
• Move one blue AC input wire from the bridge to one end of the holder, and run a new wire from the other end back to that bridge lug.
• Do the same at 6BR2 (red wires, coils) with one red wire.
• Fit 8 A slow-blow fuses in both holders.

Without these fuses a shorted bridge or lamp capacitor can overheat the wiring and start a fire if the main fuse is oversized.

Systems

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

Games

• Varkon

Related tips

• System 3 fuse chart
• System 4 fuse chart
• System 6 fuse chart
• System 7 fuse chart
• Fuse values to keep on hand for System 3-7
• Where the flipper fuse is by generation
• Main line fuse for System 3-7
• Pull the coil and lamp fuses for the first power-up

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