Need Help! Bridgeport Series 1 CNC Mill Z axis stopped working, followed by X-axis


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Thread: Bridgeport Series 1 CNC Mill Z axis stopped working, followed by X-axis

  1. #1
    Member Microtest's Avatar
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    Default Bridgeport Series 1 CNC Mill Z axis stopped working, followed by X-axis

    Hi all,

    Seen plenty of other posts on this, but figured I'd throw my situation out there to make sure I'm not under any false assumptions.

    Recently took over my father's little machine shop in southern California. I'm not well versed in machining, so I have a machinist that works the machine for the time being.

    A couple weeks ago, he had to hit the emergency stop on the machine as it seemed to skip some programming and tried to go to a different spot on the board.

    Ever since, the z axis stepper motor no longer works, but x and Y still work. It sounds like it's trying to move, but it only rotates a tiny bit whenever a step is attempted.

    I hooked the motor up to the x-axis control wiring, and the motor worked fine. So it seems to be isolated to the z control...until I had a dumb idea.

    Some folks I knew looked at it for me and said they weren't getting power to the z wires, which seemed odd to me. Regardless, I figured I'd see if I could pin down the bad wire by trying to recreate the issue on x-controls by disconnecting a single wire, X5 yellow-white. Tried moving a d to my surprise the motor rotated for the step, then stopped. Tried again...same behavior as the z-axis. Even afterchooking the wires back up to the x-motor, same behavior. So now I only have a working y-axis.

    Fuses seem okay, the have continuity and seem around the 0.5k ohm resistance.

    Looks like this bridgeport has the SMS board and diodes across the power transistors, so I'm guessing later model of the series 1 to help avoid blown transistors when E-Stop is hit.

    I swapped the X and Z SMD boards into the Y slot, and the Y axis worked fine on all of them, so I don't think its the X and Z SMD boards themselves. My only other leads are maybe the ACC board, or power transistors for the X and Z axis.

    I actually have a series 1 manual on hand,so I've been digging into that, but would rather get some other info, lest I goof this up more than it already has been.

    How best to check my transistors? Where can I get replacements? These are fairly old, so not sure if I should look for originals or identify a valid alternative for these components.

    Is there anything else I should be looking for?

    Thanks for any info or help. I've called around to various technicians, and it looks like this machine is a wee bit....aged, as there doesn't seem to be anyone who can work on these things.

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  2. #2
    Member mactec54's Avatar
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    Default Re: Bridgeport Series 1 CNC Mill Z axis stopped working, followed by X-axis

    Quote Originally Posted by Microtest View Post
    Hi all,

    Seen plenty of other posts on this, but figured I'd throw my situation out there to make sure I'm not under any false assumptions.

    Recently took over my father's little machine shop in southern California. I'm not well versed in machining, so I have a machinist that works the machine for the time being.

    A couple weeks ago, he had to hit the emergency stop on the machine as it seemed to skip some programming and tried to go to a different spot on the board.

    Ever since, the z axis stepper motor no longer works, but x and Y still work. It sounds like it's trying to move, but it only rotates a tiny bit whenever a step is attempted.

    I hooked the motor up to the x-axis control wiring, and the motor worked fine. So it seems to be isolated to the z control...until I had a dumb idea.

    Some folks I knew looked at it for me and said they weren't getting power to the z wires, which seemed odd to me. Regardless, I figured I'd see if I could pin down the bad wire by trying to recreate the issue on x-controls by disconnecting a single wire, X5 yellow-white. Tried moving a d to my surprise the motor rotated for the step, then stopped. Tried again...same behavior as the z-axis. Even afterchooking the wires back up to the x-motor, same behavior. So now I only have a working y-axis.

    Fuses seem okay, the have continuity and seem around the 0.5k ohm resistance.

    Looks like this bridgeport has the SMS board and diodes across the power transistors, so I'm guessing later model of the series 1 to help avoid blown transistors when E-Stop is hit.

    I swapped the X and Z SMD boards into the Y slot, and the Y axis worked fine on all of them, so I don't think its the X and Z SMD boards themselves. My only other leads are maybe the ACC board, or power transistors for the X and Z axis.

    I actually have a series 1 manual on hand,so I've been digging into that, but would rather get some other info, lest I goof this up more than it already has been.

    How best to check my transistors? Where can I get replacements? These are fairly old, so not sure if I should look for originals or identify a valid alternative for these components.

    Is there anything else I should be looking for?

    Thanks for any info or help. I've called around to various technicians, and it looks like this machine is a wee bit....aged, as there doesn't seem to be anyone who can work on these things.
    It will most likely be the transistors they are available as well as others that will do the job, sometimes the boards fail but mostly the transistors go, I would not mess with the Boards as this could end up with a damaged board as for finding someone to repair it for you good luck with that, there is a lot of post on here related to changing the transistors so do some searching on here under Bridgeport and you will find what you are looking for, most today have scraped the old controls are have installed new more up to date systems

    Mactec54


  3. #3
    Member mactec54's Avatar
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    Default Re: Bridgeport Series 1 CNC Mill Z axis stopped working, followed by X-axis

    Quote Originally Posted by Microtest View Post
    Hi all,

    Seen plenty of other posts on this, but figured I'd throw my situation out there to make sure I'm not under any false assumptions.

    Recently took over my father's little machine shop in southern California. I'm not well versed in machining, so I have a machinist that works the machine for the time being.

    A couple weeks ago, he had to hit the emergency stop on the machine as it seemed to skip some programming and tried to go to a different spot on the board.

    Ever since, the z axis stepper motor no longer works, but x and Y still work. It sounds like it's trying to move, but it only rotates a tiny bit whenever a step is attempted.

    I hooked the motor up to the x-axis control wiring, and the motor worked fine. So it seems to be isolated to the z control...until I had a dumb idea.

    Some folks I knew looked at it for me and said they weren't getting power to the z wires, which seemed odd to me. Regardless, I figured I'd see if I could pin down the bad wire by trying to recreate the issue on x-controls by disconnecting a single wire, X5 yellow-white. Tried moving a d to my surprise the motor rotated for the step, then stopped. Tried again...same behavior as the z-axis. Even afterchooking the wires back up to the x-motor, same behavior. So now I only have a working y-axis.

    Fuses seem okay, the have continuity and seem around the 0.5k ohm resistance.

    Looks like this bridgeport has the SMS board and diodes across the power transistors, so I'm guessing later model of the series 1 to help avoid blown transistors when E-Stop is hit.

    I swapped the X and Z SMD boards into the Y slot, and the Y axis worked fine on all of them, so I don't think its the X and Z SMD boards themselves. My only other leads are maybe the ACC board, or power transistors for the X and Z axis.

    I actually have a series 1 manual on hand,so I've been digging into that, but would rather get some other info, lest I goof this up more than it already has been.

    How best to check my transistors? Where can I get replacements? These are fairly old, so not sure if I should look for originals or identify a valid alternative for these components.

    Is there anything else I should be looking for?

    Thanks for any info or help. I've called around to various technicians, and it looks like this machine is a wee bit....aged, as there doesn't seem to be anyone who can work on these things.
    Another thing to check seeing you have the manual is that all the voltages are correct

    Mactec54


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    Default Re: Bridgeport Series 1 CNC Mill Z axis stopped working, followed by X-axis

    Just an update.
    I ordered some MJ16012 Transistors off of ebay: https://www.ebay.com/itm/MJ16012-NPN...53.m2749.l2649
    However, these were giving me odd behavior and burned out a lot. Some searching leads me to believe these may possibly be counterfiets: https://www.eevblog.com/forum/repair...stors-on-ebay/
    After finding some equivalent transistors from NTE from a local electronics shop, I replaced them with these and saw much better results.

    I've put in an order of 2N6547 Transistors from Newark to have on hand as backups: https://www.newark.com/multicomp-pro...15a/dp/35C0741
    Although not the most robust for the application, I noticed that there were still some of these in the machine and they haven't bit the dust yet.

    I'm going to look into putting sockets into the power transistor banks to help ease replacement later on, in case things fail before I can start looking into another machine in the future.
    I wonder if anyone knows exactly what kind of diodes are across the power transistors. I've heard I should replace them with schotky diodes, but no mention of which diodes or the specs of said diode. I'd imagine most any schotky might be better than the tiny things that are currently in this thing.



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Bridgeport Series 1 CNC Mill Z axis stopped working, followed by X-axis

Bridgeport Series 1 CNC Mill Z axis stopped working, followed by X-axis