Test a TIP120/TIP102 solenoid driver with a meter

Steps

• Power off. Set the meter to diode test.
• Black lead on the metal tab (or centre leg).
• Red lead on each outer leg in turn: expect about 0.4 to 0.6 V.
• Replace any failed TIP120 with the tougher TIP102.

Systems

• Williams System 3
• Williams System 4
• Williams System 6 / 6A
• Williams System 7

Related tips

• Diode-test the TIP120/TIP102 and 2N4401
• One or a few coils lock on at power-up
• Solenoid driver test at 2J9 and 2J11 with Leon's code
• The 19 solenoid driver transistors
• Solenoid driver transistor types
• Replace failed TIP122 drivers with TIP102
• TIP102 is a good substitute for SE9302 coil drivers
• Quick test for shorted TIP122/TIP102 drivers

Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part Two, Clay Harrell (pinrepair.com)