Telling an opto transmitter from a receiver

Steps

• Set the meter to diode test and check across the two leads both ways.
• A transmitter reads about 1.5 one way and open the other way.
• A receiver reads open both ways in the dark. With a flashlight shining on it, it reads open one way and near 0 (shorted) the other.

Systems

• WPC Alpha-Numeric
• WPC Dot Matrix
• WPC Fliptronics
• WPC DCS
• WPC-Security (WPC-S)
• WPC-95

Related tips

• Testing an opto receiver
• Replacement opto transmitter and receiver pinouts
• Mounting a replacement opto receiver
• Replacing trough transmitter and receiver optos
• Opto does not work: check 12 V at the transmitter connector
• Optos test good but still don't work: the opto board
• Replacement opto receiver dead or weak: try it with the notch the other way
• New opto transmitter does nothing: leads may be reversed

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