(Topic ID: 175073)

What causes transistor to keep shorting?

By kguenther6

2 years ago

Topic Stats

  • 6 posts
  • 4 Pinsiders participating
  • Latest reply 2 years ago by kguenther6
  • Topic is favorited by 1 Pinsider


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#1 2 years ago

I have a Centaur II and the transistor that controls the outhole kicker keeps shorting and the coil locks on. I have replaced the transistor numerous times along with the coil, driving diode, driving resistor, and the U1 driving chip. But the transistor will keep shorting and locking the coil on after about 10 games. It only happens on this one transistor. I have checked to make sure the coil is not shorting against anything. When the transistor shorts out it still tests good with a MM but after replacing the transistor it fixes the issue for about 10 games. Any idea what would cause this?

#2 2 years ago

I'd check through board and across board continuity. A crack in a trace can drive you nuts.

LTG : )

#3 2 years ago
Quoted from LTG:

I'd check through board and across board continuity. A crack in a trace can drive you nuts.

I'll do that. Thanks for the tip Lloyd. Your always very helpful.

#4 2 years ago

I had a coil that would lock on repeatedly on my EBDLE. Turns out the solenoid power wire was run too close to the playfield edge and was getting pinched and grounded intermittently when the playfield was down. It drove me nuts because the problem went away when the playfield was up.

#5 2 years ago

If the transistor still tests good perhaps it's not really shorting out but when you replace it something gets temporarily changed that hides the problem for a while? You could rig in a switch in series with the coil and hang it out the coin door, play till it locks on then quickly flip the switch to open the circuit and keep from frying anything then test the whole circuit in that state, briefly flipping the switch back on for very short periods if required. I did something similar on JP when I had it and couldn't figure out which coil was locking on before the fuse blew (turned out to be the raptor pit). Good luck!

#6 2 years ago

Thanks for the additional tips. And the more I think about Lloyd's answer I don't think a crack in the trace would lock the coil on. I would think that would keep it from energizing and not cause it to lock on. But Lloyd is a lot smarter than me about these things so I'll still check it out along with the other tips. Thanks again.

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