Duet 3 6HC - Short to ground issue.


  • administrators

    We have discovered that there is an issue that affects a proportion of Duet 3 mainboard 6HCs with serial numbers starting with WD41xxx. This issue occurred part way through the production run and was not picked up by our test equipment. I am very sorry for the inconvenience, wasted time and frustration this has caused our customers, we are going to put it right.

    We are investigating the issue now, as well as determining the range of serial numbers that this affects.

    If you have a Duet 3 6HC board that gives "short-to-ground reported by driver(s) x" please can you email info@duet3d.com with the board serial number and an M122 printout that shows the short to ground issue on the affected drivers. You do not need to open a separate thread about this at this time.

    Once we know the cause of the issue we will arrange replacement hardware if necessary.

    We are contacting our resellers and asking them to pause sales of Duet 3 6HCs until we know the range of boards this affects.



  • I would like to buy Duet 3 Main Board 6HC, Duet 3 Toolboard 1LC - 3 pieces, Duet 3 Tool Distribution Board and PanelDue 7i. This is not available on your site.

    Where i can buy these boards? On the site of your resellers, I do not find the entire set of boards.

    As for the error in the 6HC board, I can fix it if you tell me where to cut the tracks.


  • administrators

    @Dep drop me a line, info@duet3d.com and i will get back to you once we have confirmed the issue with 6HC



  • @Dep All of those are available at Filastruder, aside from the Duet 3 which is being held during the investigation.



  • @T3P3Tony said in Duet 3 6HC - Short to ground issue.:

    @Dep drop me a line, info@duet3d.com and i will get back to you once we have confirmed the issue with 6HC

    Thank you, I'll write a letter.

    @elmoret said in Duet 3 6HC - Short to ground issue.:

    @Dep All of those are available at Filastruder, aside from the Duet 3 which is being held during the investigation.

    DUET 3 MAINBOARD 6HC - Sold Out



  • Right, as mentioned, Duet 3s are being held while an investigation is carried out. This is affecting all Duet 3s worldwide. Once the investigation is complete, we'll resume sales. I know for a fact some of the boards we have are good.



  • Do you know what the issue with these boards is? Wrong current sense resistor? Bad FETs? I would like to debug the board I have but don't want to void the replacement warranty.


  • administrators

    @TDK said in Duet 3 6HC - Short to ground issue.:

    Do you know what the issue with these boards is? Wrong current sense resistor? Bad FETs? I would like to debug the board I have but don't want to void the replacement warranty.

    It's looking like a bad batch of diodes, which should have been picked up by the ATE, but unfortunately the test procedure was abbreviated without my authorization. We expect to have a definite answer by Monday.

    [If Marvin is listening, it looks like we are going to be replacing a lot of diodes!]



  • Which diodes, out of curiosity? I'm not seeing anything relevant on the schematic, could be blind though.


  • administrators

    @elmoret said in Duet 3 6HC - Short to ground issue.:

    Which diodes, out of curiosity? I'm not seeing anything relevant on the schematic, could be blind though.

    Looks like the v1.01 MB6HC schematic is not yet on github.



  • Didn't even know there was a v1.01!


  • administrators

    I've just added the v1.01 schematic, https://github.com/Duet3D/Duet3-Mainboard-6HC/blob/master/Duet3_Mainboard_v1.01/Duet3_MB_Schematic_v1.01.pdf. The diodes concerned are in parallel with the driver output mosfet gate resistors.



  • I probed the 8 diodes on my non-working driver 1. All 8 show a diode drop of 0.225-0.230 V.

    All 8 on the working driver 0 show the exact same reading.

    Just a data point.



  • Ouch, been there done that .. feeling the pain!

    Weller WMRT<3


  • administrators

    @TDK said in Duet 3 6HC - Short to ground issue.:

    I probed the 8 diodes on my non-working driver 1. All 8 show a diode drop of 0.225-0.230 V.

    All 8 on the working driver 0 show the exact same reading.

    Just a data point.

    Thanks for the data point. Can you try probing the resistors that they are connected in parallel with instead? I have a suspicion that the diodes may not be making contact with some of the PCB pads due to oxidation on the leads. It takes only 1 of 16 pads to not make contact to get the S2G error.

    BTW I found that none of my multimeters can measure the diode because of the 150R resistor in parallel. It seems that my multimeters don't supply enough current for this test. So when I receive a faulty board later today I will test them using a 1.5V battery in series with a 100R resistor and a multimeter set to read mA.


  • administrators

    I've confirmed that the problem is caused by the soldering between the 6-pin dual diode packages and the board being bad. Here is an example.

    2020-08-07 13.04.53.jpg

    The front left pin is not soldered down.

    This only seems to be a problem when the diodes have manufacturing code KAXS4 engraved on them. I believe that the pins on one or more reels of diodes with this manufacturing code were oxidised or otherwise contaminated, so that proper soldered joints were not always obtained.



  • @dc42

    Hello everyone ! duet 3 6ch ordered and arrived about 3 days ago to this code (WD41xxx) and diodes (kaxs4) but are all defective or will some be good? i'm only trying movement without printing. what kind of problem should i see? thank you!



  • You would see a short to ground error, and the affected motor not moving.



  • @elmoret
    hi in case of future problems will they be under warranty for how long? or do they have to replace them? what will they do?



  • Yes of course, Duet's warranty information is publicly posted: https://www.duet3d.com/warranty



  • @dc42 said in Duet 3 6HC - Short to ground issue.:

    I've confirmed that the problem is caused by the soldering between the 6-pin dual diode packages and the board being bad.

    I can confirm this issue on my board as well. Probing across the resistor gives different results than across the diode pins.

    Interestingly, it looks like one of the diode packages on my board was reworked. Maybe the assembly house spotted the issue during inspection and tried to fix in some cases (but clearly not all).

    rework.jpg


  • administrators

    @elmoret said in Duet 3 6HC - Short to ground issue.:

    You would see a short to ground error, and the affected motor not moving.

    To clarify: if any of the 4 diode packages associated with each driver is not properly soldered, then if you are using 24V power, you will get a short-to-ground report and the motor concerned will vibrate or not move at all. But if you use 12V power, you will most likely not get a short-to-ground report and the motor will move normally.

    At this stage we do not know whether all boards with KAXS4 marked diodes are likely to be affected, however it does appear that the issue affects more than a single reel of diodes.



  • @dc42

    Hello everyone! as already said my duet 3 6ch card arrived a few days ago and one of those interested cod. (WD41xxx) diodes (kaxs4) I have tried all 24 volt drivers for now they all work no errors!


  • administrators

    Hi Tony, thanks for the info. That aligns with what we are seeing, not all diodes soldered badly.

    What is your board serial number?



  • @T3P3Tony

    Hello ! and this right?
    20200811_155337.jpg


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