(Topic ID: 329980)

Coil replacement now blowing F4 fuse

By Mikenindy

2 days ago



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  • 31 posts
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  • Latest reply 11 hours ago by Mikenindy
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    #1 2 days ago

    I have a 1986 Road Kings good working condition except for one pop-bumper would operate by hand on occasion… Ordered a new coil it turned out to be bad so I put the old one back in now it immediately blows a fuse when the machine is turned on… Can’t find any pinched wires… The wires were put back in the proper position… My solder joints aren’t perfect but they seem to be adequate to me… Any suggestions guys? Thanks for any help this is my first pinball game

    #2 2 days ago

    So coils aren't bad. You can't get a new coil and it's bad, its just copper wire wound around. Define what bad means.

    Likely when you put one or both of them in, you didn't do it the proper way. Make sure the diode painted side is connected to +48V or whatever voltage your game runs at. If you don't own a multimeter, buy one for $20. The resistance setting will let you know if a coil were burned out (the copper wire itself melted). Pinball Repair Help on Facebook is another good group to join.

    #3 2 days ago

    The new coil had .08 ohms… All my others have 4.. including the one I thought was bad.. I was told the new coil was no good Because of that reading

    #4 2 days ago

    If the old coil worked before, are you 100% sure you didn't solder the wires backwords, causing it the short (bypass the coil and go straight through the diode).

    Where did you buy that coil from? Sounds supsicious.

    #5 2 days ago

    The vendor on eBay is called money machines… And yes there is something not right… The coil they had pictured is not what they sent me ..all over the numbers match up though .. So will it cause any damage if I reverse these leads and give it a try? Although I’m pretty certain I did it right… Red wires go on right… As how I remembered it not too complicated lol

    #6 2 days ago

    Right now neither wire is soldered could I just use two jumper wires just to try it out?

    #7 2 days ago

    Yea don't buy coils off Ebay. You can always use the multimeter with the coil not in circuit to verify which wire is the high voltage. I don't like to suggest this, but if you have NO fuses on hand, you can tap a jumper wire temporarily across the fuse legs to see if the coil shorts or not.

    #8 2 days ago
    Quoted from Mikenindy:

    The vendor on eBay is called money machines… And yes there is something not right… The coil they had pictured is not what they sent me ..all over the numbers match up though .. So will it cause any damage if I reverse these leads and give it a try? Although I’m pretty certain I did it right… Red wires go on right… As how I remembered it not too complicated lol

    The wire orientation does not stay the same on all coils. You MUST look at the Diodes on the coil to determine which side the power wire and ground go on. If you do not understand, STOP before doing anything else. Take a picture of how you had the wires. Compare to other Coils. Do not focus on which side of the coil the wires are, but rather their orientation in relation to the diode

    #9 2 days ago

    I’m positive I had the leads in the proper position because As on all my coils the red wire supplying voltage is on the same side as the silver stripe… I had several more coils delivered after the first one that shows only .08 homes… And all the others I received show four ohms.. I even tried disconnecting the bracket completely from the play field and setting it on something non-conductive and it still blew the fuse.. just wanted to rule out one of the insulators being bad that separates the contact points

    #10 2 days ago

    "except for one pop-bumper would operate by hand on occasion"

    Can you explain what that means. Elaborate. In solving your original problem if the coil was good it was good. May have 2 problems now. Sounds like you may have a switch contact that is super close that a small wiggle or something triggered the pop bumper. Post a YT video of your problem and post on pinball repair help group on facebook or here.

    #11 2 days ago

    Well if I took and put a finger on each side of the skirt and pushed down on occasion it would pop but not with much force.. As you can see in the photo the red wire was on the correct side

    image (resized).jpg
    #12 2 days ago

    Did you check the activating switch? Its the switch near the spoon that is activated by the skirt.
    If that switch got stuck closed, or shorted by solder that could blow the f4

    #13 2 days ago

    Well that’s what I was thinking that’s why I disconnected the entire bracket from the play field… Could that still be the issue even if the bracket is disconnected altogether from the popper legs?.. It’s got to be something simple like that clearly there is power going to the coil in my mind anyway… Can I eliminate there being anything wrong in a board?

    #14 2 days ago

    Well when I first took that apart I saw that one of the copper contacts… Not one with the little contact point on it…a”blank” one Seem to have a twist in it so I bent it Back into a flat position

    #15 2 days ago

    If you cant tell if the switch is closed, you can put something like a cut piece of cardboard between the two contact points. That might help determine if it was stuck closed..

    #16 2 days ago

    I just looked at the contacts just under the spoon They are not stuck together by any means.. Visually compared everything to the other three operating poppers they all look exactly the same to me.. i’m 60 years old… This is not all entirely new to me I have been fixing things since I was 15 years old.. This was to me a very easy straightforward repair… I can find absolutely no reason why this is happening unless it’s in a board

    #17 2 days ago
    Quoted from Mikenindy:

    I just looked at the contacts just under the spoon They are not stuck together by any means.. Visually compared everything to the other three operating poppers they all look exactly the same to me.. i’m 60 years old… This is not all entirely new to me I have been fixing things since I was 15 years old.. This was to me a very easy straightforward repair… I can find absolutely no reason why this is happening unless it’s in a board

    Easy to tell if it’s the board. Remove switch inputs, turn game on. If coil still activates/blows fuse. You likely have a bad transistor. Is the coil activating at all before fuse blows or is fuse blowing instantly?

    #18 2 days ago

    Honestly I don’t know if it was activating or not before the fuse blew… I don’t recall it doing anything… How do I remove the switch inputs?… Thanks for jumping in

    #19 2 days ago

    He's suggesting unplugging the switch that goes to the spoon however you can but it sounds like the switch is not in contact as you said. Pretty obvious either the two metal leafs are touching or they aren't so probably not the issue.

    So the original issue was that one pop bumper seemed weak? Right? I'd set it back up how you had it if possible. You can un-solder two pop bumper and switch their second legs. Tap on the other skirt input and see if the pop bumper is what you want. That tells you if there is any electronics before hand not working. Otherwise, it may just need a new coil sleeve or its a mechanical issue slowing it down.

    #20 2 days ago

    not meaning to interfere, just trying to understand what has happened.....possibly help?

    1. so the original coil, the lower pop bumper coil, seemed sluggish so you replaced it? I assume lower pop bumper by the blue/black wire not connected.

    2. the coil you replaced it with was faulty, taking out a fuse and confirmed to have a minimal resistance reading on the 'kick/flip' winding?

    3. you then replaced the faulty new coil with the original coil that was sluggish and it's now blowing the solenoid fuse although wired correctly?

    if this is the case i'd personally replace the original coils diode 1N4004 or higher like 1N4007. You may have a direct short across the diode?
    also check/test the driver transistor Q79 as it may be shorted, also check/test the pre-driver transistor Q78 (2N4401) and after doing all this and the fuse keeps blowing (if i've understood correctly) it then may be the logic IC 7402?

    #21 1 day ago

    I appreciate your help and everybody else’s… Got a snow day off from work… So without having an extra new diode on hand I just installed the coil with .08 ohms resistance as a way of eliminating a bad diode on the one that is in now… It also immediately blew the fuse… funny I can’t find Q 78 or 79 on this board or anywhere else this is what I see

    image (resized).jpg
    #22 1 day ago

    No regular coil with a resistance of 0.8 ohms is going to work, that's a dead short.

    If you disconnect the input connector and output connectors to the special solenoids (this is what your pop is in that game) you can use your meter and measure the output pin - if it's connected to ground, it's shorted on the board.

    J18 is input, J19 is output, which hopefully are labeled the same on the rottendog board.

    This does end up being a pretty simple circuit, the input gets grounded, which directly fires the solenoid. On the original board it's a logic chip to a predriver transistor to a driver transistor.... RD looks like they leave out the predriver.

    #23 1 day ago

    They are not labeled input or output but you can see the double white rectangles on J 18 and a single one on Jay 19

    image (resized).jpg
    #24 1 day ago
    Quoted from Mikenindy:

    They are not labeled input or output but you can see the double white rectangles on J 18 and a single one on Jay 19

    they wouldn't be labeled as inputs or outputs, but that's good that the labels otherwise would be the same

    #25 1 day ago

    OK… Not sure what I’m supposed to do from here… I just have had a desire to learn to fix things on my own… Let me ask you this can the diode be tested while still attached to the coil or does it need to be separated

    #26 1 day ago

    No, you can't test the diode in situ. Have to lift one side. Since you have to do that anyway, just replace it. They're cheap. 1n4004.

    You need to test the input side to the output side. If you put the meter on the output pin and it's shorted to ground, you have to either go back to the next component up and test it or just shotgun it.

    The easiest way to test it is with a logic probe, you put the probe on the input then the output - the first time you get a result you don't expect, the component in the middle is bad.

    You can compare the readings from one circuit to another to help.

    #27 1 day ago

    OK I was pretty sure that you couldn’t ..my knowledge is basic and just a little above.. . I had a friend that worked on the avionics in F 16s and Apache helicopters… I went and bought a new diode that was not the issue.. however I pulled J 18 ..and left J 19 plugged in and it blew the fuse.. But not vice versa

    #28 1 day ago

    I should have asked what board set you had, I assumed it was original.

    1J 19 is the output for the 6 'special solenoids' and the flippers, hence the plugs being 6 & 2.

    Not knowing Rottendog boards, but reckon the 6 transistors next to 1J 19 will be for your special solenoids.

    Assuming you have a multi meter, if you set it to continuity/beep and have the probes either way around and with one probe on any ground, if you touch the metal tab on any transistor and you have continuity/hear a tone, then that transistor is shorted internally and needs changing.

    #29 19 hours ago

    Yes I have a multimeter sounds like something I can manage thanks!!!

    #30 19 hours ago

    And according to the person I bought them from that board has been replaced

    #31 11 hours ago

    Thanks for your help I believe with your knowledge I found out what’s wrong… The first resistor beeped that I touched and none of the other five

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