What the System 80 ground modifications achieve
The mandatory part bonds cabinet ground solidly to the ground of every board. The optional part keeps solenoid ground separate from logic ground, joining the emitters of all driver board solenoid transistors except Q57, Q61 and Q63; any 74175 chip's pin 8 on the driver board is a good logic ground test point. Keeping them separate stops coil voltage or noise reaching the logic if the solenoid ground fails.
Systems
Related tips
- What the System 80 driver board transistors drive
- System 80 driver board transistor types
- One driver board fits every System 80, 80A and 80B game
- Test driver board outputs by grounding transistor tabs
- Run the System 80 lamp (16) and solenoid (17) tests
- Ground mod step 5: direct ground wire to the driver board
- Use heavy wire for the optional driver board ground jumpers
- Optional ground mod steps 2 to 9: driver board ground jumpers
Source: Repairing & Upgrading Gottlieb System 80 Pinballs from 1980 to 1989, Part One, Clay Harrell (pinrepair.com)