Switch column 3 dies, or rows flash on and off in switch edges test.

Indiana Jones: left slingshot switch touching a GI socket

Cause: A GI lamp socket sits right next to the left slingshot switch rivets; if they touch, 6.3 V AC reaches the green/brown column 3 wire and can kill U20 (ULN2803) or just upset the matrix.

Checks

• Inspect the left slingshot switch and the GI socket beside it for contact.

Fix

• Separate and insulate them, then replace U20 if it failed.

Systems

• WPC DCS

Games

• Indiana Jones: The Pinball Adventure

Related tips

• Row or column "ground short" errors
• Switch columns to U20 pins
• Testing CPU switch columns with the switch levels test
• A whole switch column stops working: replace the ULN2803 column driver at U20
• Switch matrix chips on the CPU board
• One switch does not work
• "Check Fuse F114/F115" (F106/F101 on WPC-95): step-by-step
• "Check Fuses F114/F115" (F106/F101 on WPC-95) message

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