(Topic ID: 16948)

Coils Burning Up

By PinballGiant

9 years ago



Topic Stats

  • 8 posts
  • 4 Pinsiders participating
  • Latest reply 9 years ago by PinballGiant
  • Topic is favorited by 2 Pinsiders

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#2 9 years ago

Most likely a locked on transistor. Find the transistor on the board and do a quick check to see if it is shorted. I do this on all games I purchase. With the power off, meter on continuity, put one lead on a good ground and the other lead on the metal tab of the transistor. If it shows continuity, it's bad. Check them all.

2 weeks later
#6 9 years ago

Jokerz is a system 11B game....After Big Guns (an earlier 11B), WMS moved the coil diodes to the auxiliary board. So, it's no worry that your coil doesn't have a diode...Unless it is a flipper coil.

The quick and dirty test of testing continuity between the metal tab of the driver transistor and ground with power off usually reveals a locked on shorted transistor but not always. I would use Clay's guides and test the driver transistor, the pre-driver transistor and the diode on the board. One of those is likely fried. When a coil goes bad, it either opens up (no resistance), or shorts (zero resistance). Opened up it just doesn't fire. Short, it's going to blow the fuse. A coil isn't going to burn up unless it's being held on by a faulty driver circuit, so that's where I'd be looking.

I would replace both damaged coils, and briefly turn the game on to see if they are both still locked on. If so, shut the game off and start testing/replacing the transistors and diodes on the board.

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