More than ten backbox lamps that are wired together with bare bus wire are all dark.

A whole string of backbox lamps is out: blown GI fuse F110

Cause: These are general illumination lamps fed from the transformer through the GI fuses on the power driver board (wired in parallel, not series); the GI fuse F110 had blown.

Checks

• Check the GI fuses on the power driver board and confirm their values against the manual.
• Inspect the GI connectors at the driver board for burned or oxidised pins.
• A corroded socket only affects its own lamp, not the whole string.

Fix

• Replace the blown fuse with the correct value. If the board still has the original large GI diodes, members advise replacing them with jumpers.

Systems

• WPC-95

Games

• Scared Stiff

Related tips

• Remove or bypass WPC-95 GI diodes D25 to D32
• One GI string is out
• Lamp matrix fuse F114 (F106 on WPC-95) keeps blowing
• A whole lamp row or column is stuck very bright
• None of the controlled lamps work, or they light in the wrong pattern
• Lamps light twice in the all-lamps sweep, or two lamps act as one
• GI string dead after connector replacement: broken traces
• 12 V unregulated LED out on the driver board: open track to C8

Source: Pinball Repair help group!! (Facebook group)