Bench testing a GI triac with a 9 V battery

Steps

• A meter's diode test only shows a shorted triac, so remove the triac from the board for a real test.
• Connect MT1 to the battery negative, MT2 to one lead of a #44 or #555 test lamp, and the lamp's other lead to the battery positive.
• Tie the gate to MT1 through a 50 ohm resistor.
• Briefly move the resistor from MT1 to MT2: the lamp should light.
• Move the resistor back to MT1: the lamp should stay lit.
• Reverse the battery and repeat; it should behave the same.

Systems

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

Related tips

• Checking GI triacs with the game on
• Replacement GI triacs
• Triacs switch AC lamps

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