Relay and coin counter transistors on the driver board
MPS-U45s Q1, Q2 and Q3 drive the game (Q) relay, tilt relay and coin lockout coil. The lockout coil is on nearly all the time; without it the door rejects coins. Q54, Q55 and Q56 (solenoids 3, 4 and 7) were for optional mechanical coin meters wired at A3-J6 and are normally unused, so they can donate an MPS-U45 for a repair; that is also why test 17 skips solenoids 3, 4 and 7.
Systems
Related tips
- Test the driver transistors while the board is out for the ground mod
- System 80 driver board transistor types
- Test driver board outputs by grounding transistor tabs
- Driver board transistors that look stuck on in a test fixture
- Diode-test the driver board MPS-U45 and MPS-A13 transistors
- A meter test of a transistor is not conclusive
- Diode-test a driver board 2N6043
- Diode-test a driver board 2N3055
Source: Repairing & Upgrading Gottlieb System 80 Pinballs from 1980 to 1989, Part One, Clay Harrell (pinrepair.com)