Test MPS-A42 and MPS-A92 display transistors
Steps
- Game off, meter on diode test.
- MPS-A42: red lead on the centre leg, black on each outer leg: 0.5 to 0.7.
- MPS-A92: black lead on the centre leg, red on each outer leg: 0.5 to 0.7.
- On a D-8168 board, test them all and replace any that fail.
Systems
Related tips
- Rebuild the high-voltage section of a 520-5047-00/-01/-02 supply
- How a Bally display board drives its glass
- Master display board versions
- Which UDN6184 drives which display
- All score displays dead
- UDN display driver chips
- Using a logic probe on the display board safely
- One score display dead
Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part Three, Clay Harrell (pinrepair.com)