Testing the Q45 2N3055 and its resistor
Steps
- Meter on diode test. Black lead on the metal case: red on the top leg reads 0.4-0.6, red on the bottom leg reads nothing.
- Red lead on the top (base) leg: black on the bottom leg (emitter) and then on the case (collector) should each read 0.4-0.6.
- Any other reading means replace the 2N3055, and also suspect its MPS-U45 pre-driver at Q29.
- Measure the large 9.1 ohm 1 W resistor beside it: 9 to 10 ohms in circuit.
Systems
Related tips
- Optional ground mod step 1: ground the 2N3055 cases on the driver board
- System 80 driver board transistor types
- How driver board coil transistors are switched
- Spare transistors for System 1 boards
- How many coils the driver board can fire
- Which driver transistor fires which coil
- Driver transistors Q1-Q4: relays and spare outputs
- Meter transistor tests are not conclusive
Source: Gottlieb System 1 Pinball Repair from 1977 to 1980, Clay Harrell (pinrepair.com)