Flipper Dual Coil Getting Hot

[Bob]

I know I should be using programming and not an EOS switch, but....

Hi Everyone, 

I've attached 3 pictures to show how I've got it wired, which i thought was right.

On bench, flipper actuates and also holds when connecting black wire to same on power supply but holding for prolonged periods makes the coil very hot.

the eos switch is normally closed (pics 1 & 2) and opens when flipper is activated.

ie it's doing everything it should but just gets really hot.

Coil ohm readings all within spec when tested on its own and EOS switch also breaks continuity when button held.

Any ideals why coil is getting hot?   

[Bob]

[Bob]

[Max Power]

How many volts are you running?  How many ohms at rest and at end of stroke?

Make sure it's wired up the same as a system 1 game and the EOS is opening fully.  Not saying this is your problem but my spare coil only has 1 diode.

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[Bob Prince]

running 48v

ohms at rest and end of stroke on which coil? 

eos is opening fully (see pic and verified with meter

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On Jun 15, 2025, at 1:53 PM, Max Power <maxxxp...@gmail.com> wrote:



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[Max Power]

That's a 24V coil.  I typically run them at 26V.  48V is going to cook them, as you've figured out.

To view this discussion visit https://groups.google.com/d/msgid/mpf-users/DD33BEE2-074B-46BA-A9BD-F4B0016913DA%40rogers.com.

[Bob Prince]

i think that did it. thanks!

is there a data base where you can check that ?

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On Jun 15, 2025, at 2:59 PM, Max Power <maxxxp...@gmail.com> wrote:



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[Bob]

Following up on the previous.

It worked. By switching to a lower voltage, coil did not heat up. Appreciate the help!!

I also tried my other 24V coils and they all worked without heat up.

 

So.. since I my system is running 48V and my other coil assembly has a Bally AQ-25-500/34-5050 48V coil I ordered that coil and just to be safe an additional entire Bally flipper assembly which included another (same) coil.

When I received the new coil, I installed it, raised the voltage to 48V but to my surprise it didn’t work, even though it’s wired correctly and I know it’s correct.

I then tried the new coil assembly and it too didn’t work.

At that point I reinstalled the 24V coil, lowered the V to 24 but to my surprise it didn’t work either, even though it did 2 days previous.

 

I then suspected the power supply but the voltage measures correctly.

The strange thing is that when I connect either the 24V or 48V coil and activate it by grounding, the coil will engage if I give the cam a little nudge.

It will then disengage when I release the ground as it should.

 

Can this still be the power supply? An issue with the soldering?

I tested the coils and they are in spec and the relay switches do work, its just seems to engage the flipper I have to nudge the flipper assembly cam even though it does not feel like it’s sticking at all.

Alos seems weird that it all worked 2 days ago

Any ideas?

[Mike Pegg Bigg Deal Custom Guitars]

If that sleeve is not installed correctly, it will bind. Also be sure there isn't any trash, or tight spots where the shaft goes into the sleeve. If it does not move mega smoothly by hand, it will need to be checked for alignment,  and sleeve.

To view this discussion visit https://groups.google.com/d/msgid/mpf-users/1d522f26-a5d6-4e87-9ecf-76bacd5e2bf0n%40googlegroups.com.

[Bob Prince]

thanks for the quick reply.

the sleeves seem to go in very easily and no binding.

that would sound like a reason for one maybe 2 not working but all?

can it be the power supply even though voltage measures ok?

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On Jun 19, 2025, at 6:15 PM, Mike Pegg Bigg Deal Custom Guitars <pegg...@gmail.com> wrote:



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[Mike Pegg Bigg Deal Custom Guitars]

Do you have 48v at the coil of each flipper mech? And do you see voltage on a meter after you push the flipper button? 

Are you running fast, cobra, or p3?

To view this discussion visit https://groups.google.com/d/msgid/mpf-users/A075729F-0B6A-4BBE-952B-9B41B3474307%40rogers.com.

[Bob Prince]

yes 48v at the coil measured across end posts 

yes see voltage on the meter across end posts after pushing flipper 

i’m running cobra but i’m just testing this on the bench

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On Jun 19, 2025, at 6:23 PM, Mike Pegg Bigg Deal Custom Guitars <pegg...@gmail.com> wrote:



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[cobra18t]

What is your coil config in MPF? Is the flipper not working at all or just not holding?

[Bob]

I'm actually just testing on the bench.

Oddly enough it works really good if I wire it as the attached picture but don't I have the positive and negative reversed? (according to the schematic)  

Shouldn't power be coming in to the kick coil? it's almost like the diodes are reversed

[Bob]

[Bob]

On Friday, June 20, 2025 at 7:32:44 AM UTC-4 Bob wrote:

[Bob]

and just to note the EOS switch is normally closed. When I activate it per the attached it moves to open as it should

[cobra18t]

The solenoid power coming in on the hold coil is fine for this coil. That is how it was intended. The normally closed EOS shorts the hold coil until the flipper strokes.

If it works with a nudge, I would suspect the EOS.

Your EOS may need some adjustment. It needs to make really good contact for a good power stroke. Your EOS wire looks a bit thin. That wire needs to take the full current of the coil and should be equal in size to the power wires on the coil. Are you confident in the wire nut installation? 

On the coil, the soldering looks a bit rough but it is hard to tell if that is the problem.

[Bob]

Always appreciative of the replies.

Actually, it works with a nudge when I wire it the way I thought was correct. this way it works completely fine.

The EOS in the flipper I am holding  in the picture works well but I will definitely be cleaning up the wiring and soldering.

However, the new flipper assembly I bought, that has the same coil, also works when reversed wired but the EOS switch gets super hot when it disengages even though its wired like the other.

Any ideas on that?

 

You mention this reverse wiring is how this coil is intended to be wired. How did you know that?

Everything I've read, even for this coil, shows the positive coming in on the other side.

 

[cobra18t]

The power is supposed to come in on the banded side of the diode. Do not wire it opposite that otherwise you are shorting the coil through the diodes. In the picture you took, the red wire is the proper wire for the 48V.

[Bob]

I have wired exactly like the one in the previous pic (red is 48V+) that is now working with power coming in the banded side. 

This one is a brand new flipper assembly and coil. The coil is the exact same as the other one. When i activate and hold it sometimes it's fine sometimes it arcs bright blue.

I'll see if I can upload a vid. it's a different type of switch but it actually looks to be better then the other one

[Bob]

[Bob]

On Friday, June 20, 2025 at 8:59:17 PM UTC-4 Bob wrote:

[Bob]

[Bob]

[cobra18t]

One of your diodes may be poorly connected or broken as they should clamp the voltage to discourage a good arc from forming. Why is the diode in a different position on that coil? If you were connecting these coils backward before, you may have cooked a diode.

That EOS in the video may also need to be adjusted. It is not opening quite far enough so the arc remains sometimes. That is not good. Make it so there is a larger gap when the flipper is held.

On Friday, June 20, 2025 at 6:20:00 PM UTC-7 bobp...@rogers.com wrote:

[Bob]

I'll try replacing the diodes. The one is in a different position simply for ease of install.

As for the EOS switch, the gap is pretty big when it opens. Bigger then the other assembly. I was worried that is might be too big, but I'll try that too.

Again, thanks for the reply. This board is super helpful. It's not like you can ask a lot of people about this stuff!

[Bob]

Ok, i replaced the diodes and the switch and it's this coil is working too! Appreciate the help!

Interesting point. if I attach the 48V+ to the middle post it works the same. Is that unusual? 

So next i tried my Bally  AF-26-750/28-800 which i believe is also 48V.

I connected that coil the exact same way, including diodes, as the AQ-25-500/34-5050's and it works but it heats up fast in the hold position.

So obviously this one doesn't get wired the same way? The coil did check to specs on the ohms before I installed it and its a new switch that I can see is fully opening when activated.

Is there a resource that has schematics on how the various dual coils get wired? 

It's really concerning that the one i found that said it was for the  AQ-25-500/34-5050 turned out to be completely backwards  

I also have to wire a 24V  Gottlieb A-17875 dual coil to a flipper (different machine). 

I'm pretty sure this coil uses ony one diode but again I'm wondering where I can find a trustable source for schematics

[cobra18t]

Do not connect power to the middle post. This bypasses the hold coil so you will be holding with the power coil and that will burn things up.

The best thing to do is post pictures of your coil and how you would like to operate it. We can then help with suggested wiring. There were so many different coils and diode arrangements that it is difficult to give a single resource for reference. On top of that, many people are taking old coils intended for use with a high current EOS and using them as processor controlled dual coils. That is fine, but you may have to do wiring changes based on the coil.

The main sanity check is that 48V NEVER goes on the non-banded side of a diode. It always goes on the banded side.

[Bob]

Is ther no way to tell from the coil number? (all these will be installed as flippers with EOS switches).

As much as I appreciate the help, I would like to try to understand the how and why in all this.

I tried hooking up the gottlieb 24VB and it too works but gets hot (I dial down the voltage to 24V when testing that one)

EOS apears to work good and banding on diodes are as you describe. I post pics of both

[Bob]

[Bob]

[Bob]

On Sunday, June 22, 2025 at 2:27:48 AM UTC-4 Bob wrote:

[Bob]

ARGHHHHHH!!!!1

So my AQ-25-500/34-5050 coil is heating up again. I also see it arcing under the table. I'm running 48V through it so I'm thinking its the EOS switch.

This is so weird because the other flipper (same coil) is supposedly wired incorrectly but has never caused a problem.

That said, I'm going to try disconnecting the EOS switches and reprogram both coils to have the software deal with this.

I'm assuming this coil will work for this.

Here is my current code:

coils:
    c_flipper_left:
        number: 0-0-5
        allow_enable: true
        default_hold_power: 1.0
        default_pulse_ms: 50
    c_flipper_right:
        number: 0-0-7
        allow_enable: true
        default_hold_power: 1.0
        default_pulse_ms: 50

flippers:
    left_flipper:
         main_coil: c_flipper_left
         activation_switch: s_left_flipper

    right_flipper:
         main_coil: c_flipper_right
         activation_switch: s_right_flipper
 

Here is my revised code:

coils:
    c_flipper_left_main:
        number: 0-0-5
        allow_enable: true
        default_pulse_ms: 50

    c_flipper_left_hold:
        number: 0-0-6
        allow_enable: true
        default_hold_power: .2
        default_pulse_ms: 50

    c_flipper_right_main:
        number: 0-0-7
        allow_enable: true
        default_pulse_ms: 50

    c_flipper_right_hold:
        number: 0-0-15
        allow_enable: true
        default_hold_power: .2
        default_pulse_ms: 50

flippers:
    left_flipper:
         main_coil: c_flipper_left_main
         hold_coil: c_flipper_left_hold
         activation_switch: s_left_flipper
 
    right_flipper:
         main_coil: c_flipper_right_main
         hold_coil: c_flipper_right_hold
         activation_switch: s_right_flipper
 

I then wire the coils as follows:

- 48 power to middle post of each coil

- Change the coil diodes so both bands now point to the middle post 

For the right flipper:

0-0-7 wire to - of low resistance (ie main or kick) coil 

0-0-15 wire to - of high resistance (ie hold) coil 

For the left flipper:

0-0-5 wire to - of low resistance (ie main or kick) coil 

0-0-6 wire to - of high resistance (ie hold) coil 

Does this look right?

[cobra18t]

Do you really need a 50ms pulse? That seems a bit high to me. You will have to play with the pulse and hold values, but start low.

How about pictures of the new arrangement? Both the coil and connection to the board.

You say the other coil is wired incorrectly. How is it incorrect? Pictures of that?

[Greg Blythe]

I ran into an issue when using system 11 Williams coils.  It’s important to note that those coils need to be treated as a single coil in mpf for hold function.  The two windings are actually in series rather than in parallel.  My solution is to use the EOS, and to use MPF in a low power hold mode.   Otherwise, I smoke the transistors on my cobrapin.

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[Bob]

what settings would you suggest? Currently the force hitting the ball seems really good.

I will get a picture of the other coil but its wired as I described previously with the + going to the center post.

Do yo think the arcing is the switch gap? too much voltage? I find getting the gap correct very difficult.

What do you think about the idea of the software control and eliminating the eos switch? 

[Bob]

well that's discouraging! Why do they have the code for it then? 

What do you mean by using "MPF in low power hold mode"? 

[Greg Blythe]

My flipper settings:

To view this discussion visit https://groups.google.com/d/msgid/mpf-users/57efd3f6-115d-4b3e-ad50-d25e8719f8f9n%40googlegroups.com.

[Bob]

here are photos of the right flipper that works fine but apperently is not wired correctly. The red wire should be on the outside post l I

[Bob]

Update.

To start, even though my issues are with the left flipper, I moved the red lead on the right flipper to where it should be (outside post).

I then  modified my flipper settings from:

allow_enable: true
default_hold_power: 1.0
default_pulse_ms: 50

to:

allow_enable: true

default_pulse_ms: 22

default_pulse_power: 1

default_hold_power: 0.25

I also adjusted the switch on the left flipper again.

fired up the game and the arcing on eos switch much better but the ball play was definitely weaker on first strike of flipper and the left flipper would not hold very well at all.

The left coil did not appear to get hot (my original problem).

I then modifed settings as follows

allow_enable: true

default_pulse_ms: 30

default_pulse_power: 1

default_hold_power: 0.5

better ball play and left coil did not heat up. Arcing on eos switch good but ... now the right flipper is getting hot!

I then put it back  to 

allow_enable: true

default_pulse_ms: 22

default_pulse_power: 1

default_hold_power: 0.25

the right flipper coil now has a noticeable hum when i engage it 

This is really driving me crazy

[cobra18t]

Ah, OK. Yes, that previous way of wiring the right flipper completely bypasses the hold coil. You would burn up your coil or driver if you held that for too long.

There will be a hum any time you use a hold power <1.0. Once the game is under glass and music is on, you won't notice it.

[Bob]

But now that coil (right) not only hums (very noticeable when hold in on) but is getting hot. How could it work fine before but now?

[CrazyBite2007]

I am by far an expert on coils....

But excessive heat in your cois seems not a good thing. Must be something wrong.

I can't help but notice, on the pictures the poor quality of solder work to wire the coils.

I don't know if there is difference between coil manufacturing, I would guess it's pretty universal? (could be wrong....)

From seeing the pictures the three terminal coils should have 4 wire ends.

2 thick ones, 2 thin ones.

1 thick wire and 1 thin wire both on 1 terminal (usually the left or rightmost terminal) (this is the positive terminal end.)

1 thick wire on the middle terminal (the common or negative of the high power coil)

1 thin wire on the outer terminal (the common or negative of the hold power coil)

The diodes should have the white stripe facing to the positive terminal.

MPF can handle the EOS so you can bypass that. or use it. your choice.

The suggestion to start with lower pulse and hold values is exactly to save your coils from overheating if you made any mistakes. (once you determine everything is working fine, you can tweak your values to suit your needs.)

Good luck getting it resolved!

Op zondag 29 juni 2025 om 23:53:38 UTC+2 schreef bobp...@rogers.com:

[Bob]

  Success!!! I think this is finally solved! 

To summarize this for others, this started with a my left flipper coil that was overheating and had strong arcing across the eos switch when the flipper was activated. Right flipper was fine. Both coils and diodes tested good.

My initial coil settings for both flippers were:  

allow_enable: true

default_hold_power: 1.0
default_pulse_ms: 50

Fix:

1. The left flipper was actually a 24v coil and I'm running a 48V system 

     (just a note here: while it is fairly easy to find resistance ratings for various coils, it's not so easy to identify the voltage)

2. I adjusted the flipper settings to:

allow_enable: true

default_pulse_ms: 22

default_pulse_power: 1

default_hold_power: 0.25

This seemed to fix arcing but coil was stil getting hot and now humming when on held.

3. Adjusted the default hold power to 1 and tinkered with the default pulse power until now it works good and has good power

Also found out my right flipper coil (that has worked all along) was wired incorrectly. now fixed and have had several games of 8 Ball since with no issues (knock on wood) .

Thanks to everyone who chipped in to help on this, it is truly appreciated!!!