Problems with the Duet WiFi



  • Hello, I recently ordered your Duet WiFi control board, and I am having some issues with it. Upon receiving the board, I mounted it to the frame of my printer with four standoff screws, using the plastic washers on the bottom of the board. the screws I was using were very large and extended all the way to the white line on the PCB. The head of the bolt closest to the wifi module must have contacted one of the traces near the D flip-flop labeled 74HC74, because when i connected the board to power the flip flop blew and started smoking. the rest of the board still works fine and i can move the moters, but i cannot connect to the wifi module. I ordered a replacement for 74HC74, and replaced the part, but still the wifi shows no signs of life, besides the LED on the wifi chip lighting up. this makes the board very difficult to use with no wifi connection. another seemingly random flaw that i have experienced is that the board crashes and resets whenever i try to home any of the axis.
    I was recommended to buy your board by Joseph Podgorski from Project R3d, and we have tried everything to get the board working again, but to no avail. If you could help me resolve this issue and tell me what steps i should take for repairs / returns, it would be greatly appreciated.

    Thanks,
    Ben Vrakas


  • administrators

    I'm sorry to hear of your misfortune. The plastic washers are intended for use on the top surface of the board under the screw heads. If the board is mounted on standoff pillars, normally the pillars are smaller than the screw heads so no washers under the board are needed.

    My guess is that the screw head shorted one or both of the R82 pads to ground. Shorting one pad to ground would short the output of the 74HC74 to ground. Shorting the other pad to ground would short one of the microcontroller pins to ground. I would not expect either to cause smoke from the 74HC74. However, if the screw was not at the same ground potential as the board ground, then there would have been potential for much more damage, including to the WiFi module.

    So IMO the next steps would be to check whether there is a transition on pin 3 of the 74HC74 when an attempt is made to start the WiFi module, and if so to replace the WiFi module,

    Forum user W3DRK offers a Duet repair service in the US.

    The resets when you try to home an axis may be caused by incorrect endstop switch wiring. If you are using simple microswitches for as endstops, use the two outer pins on the endstop connector only.

    HTH David



  • I am troubleshooting the board. it would be helpful to know the expected resistance between 3.3v and ground. I only measure 53 ohms between 3.3 and gnd, which seems low, possibly a short. i have included an image. as for the end stops, i am using optical end stops, which i have wired correctly from instructions on the wiki. i can trigger the endsops manually and the board is not effected. when i run g28 however, the board seems to experience a software crash. it is very strange. it seems that it only crashes when the board is "looking" for an endstop input.
    Here is the link for the photo: https://photos.app.goo.gl/o4goUBbz8ZwnPlfh1


 

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