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Resolved: Prusa 3D Printer damaged fan wire short circuit

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  • Resolved: Prusa 3D Printer damaged fan wire short circuit

    I've been having problems with the 3D printer all day. Every time I go to start a print the machines blinks off and on again. It happens when the nozzle moves all the way left and hits the limit switch. I've tried jiggling wires and moving the motors and nothing seems to cause it to stop. I've pushed the x-axis limit switch and that didn't cause a problem. I've even blocked the carriage from moving all the way left and that didn't recreate the problem. When the printer was still heating a moved the carriage all the way left, hard, like the printer does as its finding home and I heard the fuse blow.
    We need to replace the fuse wherever its hiding and we need to find the short and fix it. I'm out of time for now. I have other things I need to do.

  • #2
    Sounds like a strange problem.
    I'd suspect the power connection at the print bed, those wires get a lot of repeated strain and its possible for some bridging to occur if they've came loose. I did a hasty repair job on that connection this summer when the soldered connection broke off. But you said you jiggled all the wires and didn't encounter problems, so maybe not that?

    Here is a write up on the fuses on the MK2/MMU:
    https://help.prusa3d.com/l/en/articl...use-mini-rambo


    EDIT: If it does turn out to be an issue with the print bed wiring, we can look at some different support methods. The printer enclosure actually requires a new cable clamp at that location, so it could be an opportunity to address it then.
    Last edited by Garret H; 10-04-2018, 05:56 PM.

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    • #3
      The short turned out to be a pinched fan wire and carefully aligning the wires at the back of the print head solved this. When we went to do a test print we encountered a filament jam. I had to dismantle the print head to get it out. This isn't in any manual. Jammed print heads are considered a perminent problem. This is what a jam looks like:

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      • #4
        The printer is all tuned up. New nozzle is installed.

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        • #5
          Dang good job! Thanks for all you hard work getting it back up and running Grant!

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          • #6
            Some friendly thread maintenance: now that the issue has been diagnosed and resolved the thread has been renamed for future use.
            Attached is a completed Problem & Repair log to be appended to the physical Log Book that will accompany the 3D printer.
            Attached Files

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            • #7
              It was still being twitchy so I redid the XYZ calibration, Z calibration, first layer calibration. The little test square looks like cellophane tape. I also reorientated the printer and drilled holes in the shelf far enough back to keep the filament from being tangled in the cables and built a more complete enclosure. Maybe now it will behave

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              • #8
                Great job on the fix up Grant!

                I just want to mention to those that use the printer, the optimal "Live Z-Axis Adjust" setting is no longer what it used to be (-0.720).

                When you start your print, press the Select Knob to go to the Menus.
                The second option will be "Live Z-Axis Adjust".
                Select it an press the Select Knob.
                With the latest adjustments, new nozzle, etc, the "Live Z-Axis Adjust" should be set at about 0.450 to 0.500.

                I have not done enough prints to narrow it down further but these numbers do work.
                Every time there is a new mechanical repair, adjustment or add-on, this number will probably change.

                **IMPORTANT**
                I'm not sure how many people know this but if the print bed is moved TOO FAST BY HAND, it can blow a fuse!
                If the printer is off and the bed is moved quickly, it will actually power up the front display panel !!!
                The z-axis stepper will produce power and feed it back into the controller board. Bad mojo.
                PLEASE DO NOT TEST THIS !!!! Thank you ;-)

                Jason

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                • #9
                  Thanks for the advice Jason H, the more advice we can get on operating equipment from experienced members such as yourself the better! I took the liberty of quoting your write up and adding it to the general Manuals and (now) Operations post that is stickied here. That way this type of information doesn't get lost in a thread specific to an unrelated problem.
                  Last edited by Garret H; 10-11-2018, 10:52 AM.

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