After moving the game, the trough keeps ejecting balls. Replacing both trough opto boards and the 16 opto board made no difference, and the boards' LEDs stay off.

Trough keeps ejecting balls: loose ground pin starving the opto boards

Cause: The ground pin in the connector feeding the opto boards was loose at the board end, so the optos got about 5 V instead of the 12 V they need.

Checks

• Check the opto board supply voltage at the opto board connector; it should be about 12 V.
• In switch edges test, empty trough optos should read closed and change when a ball is present.
• Inspect each opto connector pin for looseness or discoloration and reflow the board header joints.

Fix

• Repin the loose ground pin (or replace the connector) and reflow the header solder joints.

Systems

• WPC-95

Games

• Junk Yard

Related tips

• Trough opto dead after reassembly: flasher plug on a switch connector
• Trough error at boot, games start only after jiggling balls: broken trough wire
• All optos dead: lost opto ground connection

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