Test trough emitters and receivers

Steps

• Hold an infrared detector card in front of each emitter; a working one shows on the card. A digital camera with a live screen also shows the infrared light.
• Cover the emitters with black electrical tape.
• In a dim room, shine a small flashlight into each receiver and watch for it to change state in the switch test.

Systems

• Bally 6803

Games

• Blackwater 100
• Dungeons & Dragons

Related tips

• NTE replacement emitters fit the opposite way round
• Trough opto numbering is backwards
• Dungeons & Dragons and Blackwater 100 use trough optos
• "Ball missing" with all balls in the trough
• Ball missing or balls stacking in the shooter lane
• Fitting new trough optos on D&D and Blackwater 100

Source: Repairing Bally 6803 Pinball Games from 1985 to 1989, Clay Harrell (pinrepair.com)