Test an under-playfield 2N5875/2N5879 coil transistor

Steps

• Isolate it from the driver board first, by unplugging the driver board's playfield connectors or lifting the transistor's driver board wire; otherwise a bad MPS-U45 pre-driver can make a good 2N5875 test bad.
• Meter on diode test, red lead on the case, black on each leg: about 0.5 on each leg in circuit, or 0.5 on one leg and nothing on the other when out of the game.
• Black lead on the base (the leg with two wires), red on the case (collector) and then the emitter: 0.4 to 0.6 each.
• Anything outside 0.4 to 0.6 means the transistor is bad.

Systems

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

Related tips

• Check every coil's resistance before first power-up
• Coil stuck on that is driven through a playfield-mounted power transistor
• Replace a shorted coil before firing a repaired driver
• Replacements for the 2N5875 under-playfield power transistors
• Replacements for the under-playfield 2N5875
• Testing a playfield-mounted 2N5875/2N5879 with a meter
• Haunted House driver board: which transistor runs which coil
• Black Hole driver board: which transistor runs which coil

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