Optional ground mod step 1: ground the 2N3055 cases on the driver board
Steps
- Remove Q58, Q62 and Q64 (2N3055): two screws and two soldered legs each.
- Trim each mica insulator so it no longer covers the bottom screw (the one nearest the legs), then tin that bottom screw pad on the component side; it is the ground contact.
- Diode-test each 2N3055: black lead on the case and red on each leg should give 0.4 to 0.6 on one leg and nothing on the other; red on the base with black on the emitter, then on the case, should give 0.4 to 0.6 each time.
- Refit with the screws done up tight and resolder the legs.
- Check each 1 W 9.1 ohm resistor wired to these transistors reads 9 to 10 ohms in circuit.
Systems
Related tips
- System 80 driver board transistor types
- How driver board coil transistors are switched
- Ground mod step 5: direct ground wire to the driver board
- Test the driver transistors while the board is out for the ground mod
- Optional ground mod steps 10 to 12: cut the Q64 loop trace and tidy up
- Testing the Q45 2N3055 and its resistor
- Diode-test a driver board 2N3055
- 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)