(Topic ID: 118594)

Replacement coil has a diode

By Bbismuth

9 years ago

Topic Heartbeat

Topic Stats

  • 13 posts
  • 4 Pinsiders participating
  • Latest reply 9 years ago by Bbismuth
  • Topic is favorited by 3 Pinsiders


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#1 9 years ago

I am replacing a stuck coil on my Mousin' Around. The replacement part has a diode. The old one did not. How can I tell which side to put which wire on? Doesn't the diode make it directional?image-411.jpgimage-411.jpgimage.jpgimage.jpg

#2 9 years ago

According to the manual the coil called for (SM2-35-4000-DC) does not have a diode so just remove the diode from the new coil.

#3 9 years ago

Thanks for the info! we installed this new coi after replacing the transitor on the board. The transistor shorted again and now the pops won't work and we keep blowing fuses. If we wired this incorrectly, could this blow a transistor?

#4 9 years ago

If a coil does not have a diode it does not matter which way it is wired. If it does have a diode and it's installed backwards then something will blow.

#5 9 years ago

Got it. I wonder if I messed up this new coil. Maybe I should get a new one again.

#6 9 years ago

The coil is wired incorrectly in your second photo. The paired wires on the right is the hot side of the circuit that jumps from coil to coil in parallel. When the coil received a path to ground it created a dead short across the drive transistor and destroyed it and the diode. This is assuming you had the diode connected of course.

#7 9 years ago

So you installed the new coil with the diode installed?

If so and the transistor blew then the diode was probably wired backwards. I doubt if that would damage the coil, but you can check it with a DMM.

#8 9 years ago

Yeah. We installed it with the diode. I had a bad feeling and should have known better. If you don't mind, what kind of reading would a bad coil give in a DMM?

#9 9 years ago

Zero ohms or close to it in both directions, if the diode is shorted (which it now is).

#10 9 years ago

Remove (and throw away) the diode before testing the coil.

Post edited by terryb: removed link that will probably just cause more confusion

#11 9 years ago

Thanks guys. I'm a noob here and appreciate the help and patience.

#12 9 years ago

What do you mean by a 'stuck coil'? Did you check its resistance after disconnecting the wires from it? Should be around 3-10 ohms. If so, then the coil is fine and does NOT need replacing. If it's infinite resistance (open circuit) then there's a broken wire somewhere (often that short stretch between the lug and the coil windings. Near zero ohms and there's a short in the coil.

Coils rarely need replacing. They will usually look physically damaged and/or burnt if they need replacing. If it was sticking, likely culprit was a drive transistor, dirty/worn plastic sleeve, or deformed plunger. (P.S. Your original coil looks fine. Did you test it before buying a replacement?)

#13 9 years ago

Makes sense. I'll check both.

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