Burn another Coil and fuse. Don't understand everything - Cobrapin

[leeoneil]

Hello.

I have burn another flipper dual wound coil, and another fuse on the cobrapin.

I understand just a part of the problem, so maybe you can help me.

I found this wiring schematic just today... But it's too late.

Look what i did :

Black wire to the high voltage coil, blue wire to the small coil (on dual wound coil FL11629).

I was thinking the "key" plug was in the middle everywhere....

So when I put high voltage, the left flipper coil burn instantaneously (and the fuse blow).
I understand it's not wired correctly, but I don't understand why it melted down !
In MPF and with the LED it's ok, when i push the button, the "high voltage LED" flash and then the "low voltage LED" appears.

In MPF 0-0-10 is high voltage / 0-0-11 is hold flipper.

Why did the coil burn this way ?

Do you have an idea ?

Thank's for your help !

[leeoneil]

I tried with 0-0-13 and 0-0-14

It's very weird.

The high power LED are flashing !!!!

So the high power coil is regularly taking some power (multiple times in a second).

[Ryan HoltKamp]

Explain what you mean with the coil burning?

At this point, you should remove the diode and test the resistance across the three coil lugs, make sure it matches the specs for that coil.  Then check the diode with a  diode tester of your meter.  The diodes are a few cents anyway, so may be easier just to replace it.

That said, are you sure the diode on the coil is pointing toward J13 plug?  Like this image?

https://pinballmakers.com/wiki/images/c/c6/CobraPinConnectionDiagram.jpg

In my case, the diodes had a white band on one side, and the wire connected to that side had to go to J13.  The diodes are important, and will blow fuses and burn up MOSFETs on the board if it's going the wrong direction.

My coils are single wound, so my code will differ from yours, but you can see below default_pulse_ms: 10.  That only pulses the coil a very short time so you can test without blowing anything.  Look at mpf services also for an easy way to test coils.

coils:
  c_flipper_left:
    allow_enable: true
    number: 0-0-9
    default_hold_power: 0.125
    default_pulse_ms: 10

[cobra18t]

Ryan is on to something with trying to understand your definition of burning and confirming your diode directions. If you had a diode backward at some point, it would have easily blown a fuse and the transistor could have failed.

Could you share your whole config? Do you have any videos of the strange behavior? I am assuming you are talking about the yellow LEDs when you said they are flashing multiple times per second on 0-0-13 and 0-0-14?

Also, you had a picture of your coil wiring, could you re-post that?

What voltage are you running for coils? 48V? Do you have a diagram of how you are powering everything?

[leeoneil]

Hello, thank's for trying to understand something !
I'll take some photo of my cobra and my wiring, and I will share it with my config
- the diode are all oriented correctly
- yes i'm talking about the yellow LED for the flashing.
- yes I'm using a 48V for my coils
- I know that the coil is burned because it made a beautiful smoke, like If we were in a cartoon, and the fuse on the Cobra blow at the same time.

Actually, everything is working fine.... But I don't know why so it "scares" me !
I think i did just one thing : I disconnect and reconnect the wires of the "burning" coil on the Cobra.
Could a bad connection can make this "LED flashing" on the Cobra ?

And it doesn't answer my initial interrogation : why the hell did the coil burn ?
Is it possible that the "key" wiring on the Cobra send 48V ?

I'll take some photos and i'll come back, thank you !

[cobra18t]

Ah, that is probably it. Yes, the spare pin has 48V on it so people have the option to use that to power the coils (this is not generally recommended because the current capacity of that connection is not as high as the connections on J13).

With the way it sounds like you connected it, you had 48V on both sides of the hold coil. Since there is a diode from hold coil to the power coil, the 48V on the hold coil shorted through the diode when the power coil was pulsed. That diode is probably what smoked. The coil may be fine if you replace the diode. Check the resistance of both coils to be sure.

[CW Goss]

I think I just did this myself.  Didn't pay attention to the * on J6, J7, and J8 and was wiring J8 with my 2nd flipper when I did a test.  Coil blown and I lost an output channel.  Down sized my fuse.  Made sure to skip the * pin.

[cobra18t]

Are you using single or dual wound flippers?

[CW Goss]

It was a dual coil.  I have three flippers.  The other two work fine.   All HV-A, B, and C 48VDC Power connects to band side of the coil diodes.  On J8 I hooked up flipper one on 1.0.1 (main coil) and 1.0.2 (hold coil) tested SAT.  Flipper 2 on 1.0.3 (main coil) and 1.0.4 (hold coil).  This is where I think I went wrong, I connected to J8 PIN #4.  I notice now that this has the * label.  From what I'm reading this is always hot?  Tested - Hot coil, diode 1 got really hot.  Issue now with transistor 3.  J8 Blue LED only comes on when I connect the other coils.  Flipper 3 on 1.0.6 (main coil) and 1.0.7 (hold coil) tested SAT.  Hooked up the rest of my coils on J6 and J7 making sure to skip the * pin on each.  All tested SAT.

[cobra18t]

Connecting a coil to the * pin should not cause any problems by itself. The * pin is connected to one of the the HV_x pins, so yes, it should be a fused 48V. The full pin label for the * pin is on the underside of the board. So, if you have a coil by itself connected to * and 48V, nothing should happen. 

The problem comes when you forget about the * pin and get the rest of your pinout wrong and accidentally assign a hold coil in MPF to a power coil in hardware for example. The other problem that can happen is that you can have a diode bridging two coils on certain flipper coils, so miswiring can lead to shorting through that diode. Then when you try to fire that coil, you are trying to short 48V to GND through a diode. This last problem seems most likely based on your description.

"J8 Blue LED only comes on when I connect the other coils." This is concerning and points to another wiring error. The blue LED being off means your bank C fuse is blown. If it turns on when other coils are connected, it means you are supplying that bank through another coil, rather than through the fuse. Remember, coils on bank C should only be powered by the HV_C pin from J13. It sounds like one of the coils you are connecting to bank C is powered by HV_A or HV_B or maybe even an unfused 48V.

So, which is the hot coil? Which one is diode "1?" Which transistor is "3?" When a transistor fails, it usually shorts to GND which leads to the coil getting stuck on. 

Do you have any rough diagrams/pictures of your connections and the issues you see?

[CW Goss]

In general, why have the *?

Since I didn't skip the * and I was assigned the flippers in MPF as FLPR1 Main, FLPR1 Hold, FLPR2 Main, FLPR2 Hold, and FLPR3 Main, FLPR3 Hold that would mean that flipper 3 got their main and hold swapped.  I caught this the next day as I was hearing alot of buzzing from that coil when testing.  I didn't look at the underside of the board much and since it was mounted with all my DI already landed, it wasn't something I wanted to remove.  The fuse did not blow the first time I hooked this up.  I'm assuming I was overrated.  I lowered the fuse rating, and the fuse is good.  

Next day I measured voltage from PIN C to each J8 pin and it shoes 48 VDC which is not the case for J6 and J7.  The shorted transistor is Q20.  The burned diode is D52 but still checks out at 5 VDC one way on a FLUKE.  Despite this my two still good dual coil flippers still work.  I'm confused by that but they seem fully functional.

The wiring for all three flipper coils is HV -C to banded side of the first coil diode.  Main Coil lead on middle point (where the two diodes meet) and Hold Coil lead on non-banded outside point.  I tripled checked this wiring before ever attaching my 48 VDC power to avoid just this sort of thing.

Is there documentation in a diagram that shows the exact pinout of J6, J7, and J8?  I normally deal with PLC's and refer to my documentation often.  I did not learn much from the documentation on the Pinball Maker website.  It's generalized for a reason, and I understand but in order to verify correct pin assignment to MPF registers or even the board labelling something with pin to address might be helpful.  Again, once the board is mounted and becoming populated it's hard to flip it over.  I honestly didn't even realize I had a 9 pin connector til I saw the *.

My new flipper coil is ordered, and I will assign it to 1.0.6 and 1.0.7.

[cobra18t]

" In general, why have the *?"  

It is a Williams influence. They used 9 pin connectors for coils with a key pin so you did not mix up connectors. You could always snip that pin off if you want. 

"or even the board labelling something with pin to address might be helpful"

The output order is labeled in silkscreen on the board (1-0-0, 1-0-7, 1-0-6,...). The asterisk marked on the board is the only pin that interrupts that order.

From: https://pinballmakers.com/wiki/index.php?title=CobraPin#Coil_Outputs

"The 24 coils are broken up into 3 banks of 8 outputs. The 3 9-pin 3.96mm connectors are JST VH style. There is a ninth pin on the connector that can be used as a key. That pin is marked by an asterisk in silkscreen. The coil outputs are labeled in silkscreen with the MPF compatible numbers."

I will add a coil pinout table to Pinball Makers to make it clearer. If you find other things that you wish were on the page, please let me know. There have been a number of contributions from other people.

Are you saying that with the J8 connector unplugged, the blue LED is off? If that is true and the fuse is good, I can only guess that you blew the HV_C trace under the board. That is likely why you still have two working coils. Can you check? It goes from J13 and wraps around the outside of the board to J8. Pictures of electronic destruction are always appreciated. If it is blown, you should add a jumper wire between HV_C on J13 to HV_C on J8. That connection is required for the diode protection to work. I can provide repair instructions if you need.

[cobra18t]

In the meantime, here is a pinout mapping that you can use...

[CW Goss]

So here is the backside and yes it appears there is an open trace.  Not positive if it's just HV-C or maybe GND too?  What do you recommend for repair?

[cobra18t]

Solder a wire between HV_C on J13 and HV_C on J8 on the bottom of the board as shown:

[CW Goss]

Thank You for your assistance!  Solder job complete and everything appears to be normal.  I feel like a smuck for missing the detail about the key pin.

[Stefan Zeller]

Regarding to the enhancement to pinballmakers. I also burned a coil, thus I proposed an additional sentence:

Coil Outputs

The 24 coils are broken up into 3 banks of 8 outputs. The 3 9-pin 3.96mm connectors are JST VH style. There is a ninth pin on the connector that can be used as a key. That pin is marked by an asterisk in silkscreen. Be careful: This pin is not connected and using it by mistake can lead to a wrong pulse on a coil and thus can burn the fuse. The coil outputs are labeled in silkscreen with the MPF compatible numbers.

But I didn't get an answer.

BTW: You could by default cut the pin with asterisk at the coprabin board. People would at least start wondering and maybe get the point with the "key pin" :-)

[cobra18t]

I added a similar sentence yesterday. Check it out to see if it is acceptable. The pinout PDF is also there now.

[Stefan Zeller]

Thanks, perfect

[CW Goss]

Thanks!