Test driver board outputs by grounding transistor tabs

Steps

• With the game on, clip one end of a jumper wire to ground.
• Briefly touch the other end to the metal case or tab of a driver transistor (the MPS-A13s have no tab).
• A 2N3055 (Q58, Q62, Q64) or 2N6043 (Q53, Q59, Q60) should fire its coil; an MPS-U45 usually lights a lamp or two.
• Expect nothing from Q1-Q3 (relays), Q57, Q61 and Q63 (pre-drivers for the 2N3055s) and, on games such as Black Hole and Haunted House, Q13-Q17 (pre-drivers for under-playfield 2N5875s).

Systems

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

Related tips

• 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
• Ground mod step 5: direct ground wire to the driver board
• Use heavy wire for the optional driver board ground jumpers
• Optional ground mod steps 2 to 9: driver board ground jumpers
• Diode-test the driver board MPS-U45 and MPS-A13 transistors

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