Testing an under-playfield 2N5875 and its wiring

Steps

• Unplug the driver board playfield connectors (or lift the transistor's driver lead) so the reading is not upset by the board.
• Meter on diode test. Red lead on the case: black on each leg reads about 0.5 in the game (0.5 on one leg and nothing on the other out of the game).
• Black lead on the base (the leg with two wires): red on the case and then the emitter should each read 0.4-0.6.
• Check wiring: base (white/red/red plus pull-up resistor) goes to the driver board, emitter to the non-banded coil lug, case (collector) to the green ground.

Systems

• Gottlieb System 1

Related tips

• Torch: under-playfield coil transistor
• Joker Poker: under-playfield coil transistor
• Roller Disco: under-playfield coil transistor
• The Incredible Hulk: under-playfield coil transistor
• Games with under-playfield 2N5875 driver transistors
• Kings drop bank never resets: under-playfield transistor wired wrong

Source: Gottlieb System 1 Pinball Repair from 1977 to 1980, Clay Harrell (pinrepair.com)