A single string of general illumination lamps stays dark.

One GI string is out

Cause: Its fuse, a broken wire from the fuse to the bulbs, or its triac.

Checks

• Check the string's fuse.
• Measure for voltage at the bulb sockets: none means an open wire; voltage present points to the triac.

Fix

• Replace the fuse, repair the wire, or replace the triac.

Systems

• WPC Alpha-Numeric
• WPC Dot Matrix
• WPC Fliptronics
• WPC DCS
• WPC-Security (WPC-S)
• WPC-95

Related tips

• General illumination strings
• GI string dead after connector replacement: broken traces
• A whole string of backbox lamps is out: blown GI fuse F110
• One GI string dead though the board and fuse test fine: burnt connector in the cabinet
• Several GI strings dead after a connector repair: lifted pads at J115
• None of the controlled lamps work, or they light in the wrong pattern
• All GI out (playfield and backbox) with good fuses and plugs: reseat the CPU ASIC and ROM
• How the WPC lamp matrix works

Source: Repairing Williams/Bally WPC Pinball Games from 1990 to 1999, Part One, Clay Harrell (pinrepair.com)