None of the opto switches work, including the flipper buttons and drop targets.

Indiana Jones: no optos work, check J905 on the Fliptronics II board

Cause: Connector J905 on the Fliptronics II board carries the ground for the flipper opto boards and the drop target board; if it is loose, missing or offset by a pin the optos lose ground.

Checks

• Check J905 is fully seated on the right pins.
• Check its pins and wires for damage.

Fix

• Reseat or repair J905.

Systems

• WPC DCS

Games

• Indiana Jones: The Pinball Adventure

Related tips

• Indiana Jones: finding which optos make the Path of Adventure stutter
• Indiana Jones: exposed switches at the Path of Adventure get bent together
• Indiana Jones: Path of Adventure stutters when moved with the flipper buttons
• Indiana Jones: left slingshot switch touching a GI socket
• Indiana Jones: balls keep ejecting from a crushed mini-playfield switch
• Indiana Jones: flippers die, one display line lit, balls keep launching
• Fliptronics: flipper will not hold up (flutters)
• Two LM339s on the Fliptronics board read the flipper optos

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