(Topic ID: 152874)

AFM: Melted flipper coil replaced, is that the end?


By viper001

3 years ago



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  • 17 posts
  • 9 Pinsiders participating
  • Latest reply 3 years ago by Betelgeuse
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coil_short_diode_(resized).PNG

#1 3 years ago

So at my last party someone came over and reported that AFM the left flipper wasn't working. Quick investigation revealed that it was seized because the coil had partially melted. I replaced the coil to find the flipper was dead, figured out that it had blown the fuse as well. Replaced the fuse (fully expecting to encounter more problems), and weirdly it seems perfectly fine right now. That is what has me worried, is is possible a coil could have been the cause of all these problems? I guess I was expecting the new coil to lock on and have to trace down problems with a transistor upstream from the coil. I played for about 20 minutes and neither saw (nor smelled) anything wrong, flipper was working fine.

#2 3 years ago

Usually it's more involved, but I have seen coils where it shorted internally with chips in the insulation.

#3 3 years ago
Quoted from vid1900:

Usually it's more involved, but I have seen coils where it shorted internally with chips in the insulation.

That is encouraging to hear. If there is a problem still on the game, possibly after it gets hot, is there any way I can be sure without risking the new coil? Could the TIP be slightly out of spec and maybe leaking current, or is that even possible?

#4 3 years ago

It could have been also a dirty flipper button opto that caused the coil getting hot and eventually getting short.

#5 3 years ago
Quoted from wellarmed:

It could have been also a dirty flipper button opto that caused the coil getting hot and eventually getting short.

I'll give the optos a good cleaning just to be safe. Sadly, I used to know that, thanks for the reminder!

#6 3 years ago
Quoted from wellarmed:

It could have been also a dirty flipper button opto that caused the coil getting hot and eventually getting short.

Flaky flipper opto boards definitely can happen ... The flipper opto "pulses" the signal so the coil rapidly turns on/off (many times a second) and gets really hot. I had this happen once. Usually cleaning won't fix it, it's a bad opto. Cleaning the Optos can help with weak flippers though.

I also had a bad flipper chip in my TOTAN (also wpc95) which would do the same thing, the coils would get very hot during an extended game.

Another thing could be a faulty flipper circuit so that the circuitry isn't changing to holding voltage when the flipper is held up. If you played the 20 minute game without a lot of holding (ie normal quick flips) this wouldn't show up so much.

I recently bought a sorcerer where the EOS was wired completely wrong, in such a way the coil was getting full voltage all the time. The previous owner had played it like that for a year with no visible problems. One of his buddies came around and was holding a ball on the flipper for a while during multiball and it completely melted from the heat.

rd

#7 3 years ago

check mechanically to ensure the EOS switch is functioning. Also check switch matrix to ensure EOS functions.

#8 3 years ago
Quoted from rotordave:

Flaky flipper opto boards definitely can happen ... The flipper opto "pulses" the signal so the coil rapidly turns on/off (many times a second) and gets really hot. I had this happen once. Usually cleaning won't fix it, it's a bad opto. Cleaning the Optos can help with weak flippers though.
I also had a bad flipper chip in my TOTAN (also wpc95) which would do the same thing, the coils would get very hot during an extended game.
Another thing could be a faulty flipper circuit so that the circuitry isn't changing to holding voltage when the flipper is held up. If you played the 20 minute game without a lot of holding (ie normal quick flips) this wouldn't show up so much.
I recently bought a sorcerer where the EOS was wired completely wrong, in such a way the coil was getting full voltage all the time. The previous owner had played it like that for a year with no visible problems. One of his buddies came around and was holding a ball on the flipper for a while during multiball and it completely melted from the heat.
rd

Wow, some more good stuff to check. I know I have some new flipper opto boards in case that turns out to be the case. From what I"m reading I need to just play the game for a while, with a good amount of cradling and then check for excessive heat, and if it's there go down these other things.

#9 3 years ago
Quoted from viper001:

Wow, some more good stuff to check. I know I have some new flipper opto boards in case that turns out to be the case. From what I"m reading I need to just play the game for a while, with a good amount of cradling and then check for excessive heat, and if it's there go down these other things.

Yep. As Vid said, maybe just a bad coil, but I've not encountered that myself.

I'd play a 5 minute game with a heap of cradling, and see if the coils are hot after that. They shouldn't be.

rd

#10 3 years ago
Quoted from rotordave:

Yep. As Vid said, maybe just a bad coil, but I've not encountered that myself.
I'd play a 5 minute game with a heap of cradling, and see if the coils are hot after that. They shouldn't be.
rd

I have to replace one tonight. When too much cradling was done the flipper started sticking up. Saturday night I pulled the flipper mech apart expecting a mushroomed / magnetized coil stop but found the coil sleeve was very difficult to remove. So it seem some insulation is cracked inside the coil causing a short. Not enough to blow a fuse, but shortens the winding enough to generate some heat.

#11 3 years ago
Quoted from Taxman:

I have to replace one tonight. When too much cradling was done the flipper started sticking up. Saturday night I pulled the flipper mech apart expecting a mushroomed / magnetized coil stop but found the coil sleeve was very difficult to remove. So it seem some insulation is cracked inside the coil causing a short. Not enough to blow a fuse, but shortens the winding enough to generate some heat.

Òh, that is very common. The coil has seen some heat over the years, and the sleeve is hard to get out because the centre of the coil is distorted. Time for a new coil.

However coils spontaneously combusting is pretty rare.

rd

#12 3 years ago

In switch test, push the flippers forward (one at a time) and verify that the EOS switch is closed before playing a game.

#13 3 years ago

Well, EOS checked out. Left game in attract mode for 2 hours, coil still cool. Played with much cradling and the coil was still cool to the touch. I think I'm going to write this off as a bad coil. If I find out over the next couple of weeks that diagnosis was incorrect I will update this thread. Thanks for the suggestions!

#14 3 years ago

If you still have the old coil, can you check the diode located between the 'Hold' and Center lug by cutting it loose and measure continuity. In picture D1
When this diode has a short, it could give similar results.

just curious

coil_short_diode_(resized).PNG

#15 3 years ago

I just had a bad left coil on my AFM. Started to stutter when pushing the flipper button.

Checked basics first. Then removed the coil to look it over better. Came apart in the slinky effect. The stuttering was an internal thing, and I'm sure like yours would have shorted/melted soon.

LTG : )™

#16 3 years ago

I think the coil should still be in the trash, I will fish it out and check it out. That is a great idea.

#17 3 years ago

For what it's worth, a bad eos switch will not melt a flipper coil on a wpc95 game because the software will compensate for this failure. Hope you got lucky and it's just a bad coil!

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