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(Topic ID: 273343)

My plunger coil burns out !!

By Roverius

3 months ago

Topic Stats

  • 6 posts
  • 3 Pinsiders participating
  • Latest reply 3 months ago by Roverius
  • No one calls this topic a favorite


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#1 3 months ago

A few days ago, while i was testing a MPU board. The Q4 of the PPB burned out. I have replaced that and i've noticed that the plungercoil was melted.
I have replaced the coil and when i started the pinball machine, i heard some kind of high tension noise. Well, that was the coil burning again. Weird thing is, the fuse does not blow. Why is this happening? is there a problem with voltages? bad PPB or bad Powersupply board?
If i disconnect the wires of the plungercoil, should i measure some voltages?

IMG_20200719_132850 (resized).jpgIMG_20200712_164007 (resized).jpg
#2 3 months ago

Is Q4 a tip36c? Something not right here. Is this the first transistor you replaced or is this the second one that is now burnt up?
And what the heck is going on with R16? Don't think that is correct resistor.
Did you test D18?
More going on here than just what I see.
This board needs some bench test time before going back in a machine.

#3 3 months ago

That board has been serviced before, must have burned a hole in the board before. The resistance was placed over the TIP36C legs and that board worked without problems. The issue came when i tested a MPU board with issues. The Q4 burned out and the Q5 was black due to the smoke. All works well, the VUK that is on the same voltage line works also. Or, there could be a problem with the diode, but that tested out OK.
When active, what voltage should be on the brown-yellow?

It is coil 12 on the schematics

110031766_284611406194065_8113753777722233806_n (resized).jpg
#4 3 months ago

Problem solved !!

#5 3 months ago

What was the problem?

#6 3 months ago
Quoted from mtn-:

What was the problem?

The problem was that Q4 was short. E and C were short to Base and that made a constant ground (Brown-Yellow) on coil 12.
I don't know if i had received a bad TIP36C or that it has shortened due to other reason.
Replacing the Q4 again and made tests on the wires before placing a new coil was OK
Tests OK

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