No general illumination anywhere, playfield or backbox, while controlled lamps and coils work. GI fuses are good, about 7 V AC reaches the GI input plug, and a socket lights if its return is jumpered.

All GI out (playfield and backbox) with good fuses and plugs: reseat the CPU ASIC and ROM

Cause: A poor contact in the socketed ASIC (U9) or ROM on the CPU board, so the command to switch the GI triacs on never reached the power driver board.

Checks

• Check the GI fuses and the GI plugs and headers on the power driver board (J115, J120, J121) for burning first.
• Measure the GI AC at J115 to confirm the transformer side is good.
• Reseat or flip the ribbon cable between the CPU and power driver boards.

Fix

• With the power off, press down firmly on the ASIC (U9) and the ROM in their sockets to reseat them, then power up and check the GI.

Systems

• WPC-Security (WPC-S)

Games

• Johnny Mnemonic

Related tips

• No lamp matrix lamps light
• One GI string is out
• None of the controlled lamps work, or they light in the wrong pattern
• One GI string dead though the board and fuse test fine: burnt connector in the cabinet
• No GI at all
• General illumination strings
• All matrix lamps stay on
• Lamp matrix fuse F114 (F106 on WPC-95) keeps blowing

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