50 V coils on earlier System 11 games
Earlier System 11 games ran most coils at +25 V. The CPU drivers could not switch the 50 V coils directly, so each 50 V coil is fired by a small relay board under the playfield whose relay coil runs from +25 V through a TIP122 driver.
Systems
Related tips
- 50 V coil dead on an early System 11 game
- System 11 coil outputs
- What changes when fixing coils on System 11
- Where the coil diodes are on System 11
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- 50 V coils on early System 11: under-playfield relay boards
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Source: Pinball Machines: How They Work & Troubleshooting, Norbert Snicer