Testing loose transistors on the bench

Steps

• Lay the transistor printed side up with the tab away from you. TIP parts read base, collector, emitter left to right; the small plastic parts read emitter, base, collector when lying flat side up.
• Everything except the TIP36c tests the same as in the board.
• TIP36c out of circuit: black lead on the left (base) leg, red on the center and right legs: 0.4-0.6 each. Tab to center leg: zero.

Systems

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

Related tips

• 20-second test for shorted coil driver transistors
• Replace the pre-driver along with a failed driver transistor
• Which transistor drives which WPC solenoid and lamp circuits
• A diode-mode transistor test is right about 98% of the time
• Coil locks on as soon as the coin door closes: transistor shorted by the old coil
• Auto-launch fires weakly but full power when the transistor is grounded
• Left popper fires at random with the right pop bumper: shorted J127 header pins
• WPC driver board: lamps, GI and coils all dead, CPU fine: broken blanking trace

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