Diode-test the driver board MPS-U45 and MPS-A13 transistors

Steps

• These are Q1 to Q57 and Q63, and test the same in or out of circuit.
• Meter on diode test, from the solder side: red lead on the middle trace (base).
• Black lead on each outer trace in turn: about 1.3 on the emitter (on an MPS-U45, the leg nearest the bottom edge connectors) and about 0.7 on the collector, within 0.1.
• Zero or no reading means bad; 0.4 to 0.6 probably means bad too. Compare with neighbouring transistors of the same type.

Systems

• Gottlieb System 80
• Gottlieb System 80A
• Gottlieb System 80B

Related tips

• Diode-test a driver board 2N6043
• Diode-test a driver board 2N3055
• Test the driver transistors while the board is out for the ground mod
• What the System 80 driver board transistors drive
• System 80 driver board transistor types
• Relay and coin counter transistors on the driver board
• Some 80B driver boards use the coin counter transistors
• Test driver board outputs by grounding transistor tabs

Source: Repairing & Upgrading Gottlieb System 80 Pinballs from 1980 to 1989, Part One, Clay Harrell (pinrepair.com)