No 3.3V or 5V power with Vin, but...



  • ...Both LEDs illuminate when the USB is plugged in.

    The duet wifi receives 24V from the PSU. The blue Vin LED is illuminated when plugged into the wall, but nothing else. When I have the USB plugged in both the 3.3V and 5V LEDs are illuminated and the endstop LEDs function as expected. I can connect to the board using DWC (obviously only when the USB is plugged in).

    I have unplugged everything from the board except the Vin plugs, but the 3.3V LED and 5V LED still do not light up when using only 24V.

    What could be happening here?



  • @buffalo_maker said in No 3.3V or 5V power with Vin, but...:

    I have unplugged everything from the board except the Vin plugs

    Does that include the SD card? If not try removing it as well. Does anything get warm?

    And can you examine U3 closely; ref this https://forum.duet3d.com/topic/10383/u3-a4403-dead



  • Thanks for the suggestion. I just removed the SD card (along with everything else), but no luck: still only Vin from 24V. When I had it all wired up and under Vin nothing seemed to be getting hot. I specifically checked the steppers after it had been on for a while and they were room temperature.

    U3 is in good shape and I didn't notice any obvious defects elsewhere while searching for U3.



  • I think U3 is the likely suspect given the symptoms (it makes 5v, and 3.3v is made from 5v) even if it doesn't have visible damage, but at this point I think you'll have to wait for the Duet3d people if the board is under warranty. (If its not under warranty you'll probably be fine running off USB or external 5v)

    Maybe post the output from M122 (when powered by USB) while you wait, just in case there is anything of interest there.



  • Is this a recent fault or a new to you board? If new to you board check the positions of the jumpers on the board. The internal 5V regulator can be disabled when using an external 5V supply.



  • If I read the schematic correctly, the blue led is connected before the VIN fuse so theoretically the fuse can be blown and the blue light will still be on.

    https://github.com/T3P3/Duet/blob/master/Duet2/Duet2v1.04/DuetWifi_Schematic_v1.04.pdf



  • if that's the case with the fuse you could check it by measuring voltage between a heater positive terminal and a ground rather than removing the fuse.



  • @zapta said in No 3.3V or 5V power with Vin, but...:

    If I read the schematic correctly, the blue led is connected before the VIN fuse so theoretically the fuse can be blown and the blue light will still be on.

    https://github.com/T3P3/Duet/blob/master/Duet2/Duet2v1.04/DuetWifi_Schematic_v1.04.pdf

    true story!



  • @bearer said in No 3.3V or 5V power with Vin, but...:

    I think U3 is the likely suspect given the symptoms (it makes 5v, and 3.3v is made from 5v) even if it doesn't have visible damage, but at this point I think you'll have to wait for the Duet3d people if the board is under warranty. (If its not under warranty you'll probably be fine running off USB or external 5v)

    Maybe post the output from M122 (when powered by USB) while you wait, just in case there is anything of interest there.

    Running off external 5V or USB seems like the best path forward at the moment. I will post the M122 return when I have a chance later today or tomorrow.

    Unfortunately the Duet is probably not under warranty. I purchased it months ago anticipating faster progress with the rest of the printer lol.

    @DocTrucker said in No 3.3V or 5V power with Vin, but...:

    Is this a recent fault or a new to you board? If new to you board check the positions of the jumpers on the board. The internal 5V regulator can be disabled when using an external 5V supply.

    @DocTrucker said in No 3.3V or 5V power with Vin, but...:

    Is this a recent fault or a new to you board? If new to you board check the positions of the jumpers on the board. The internal 5V regulator can be disabled when using an external 5V supply.

    The board was purchased new but I will check this anyway. Can't hurt to rule out definitively.

    @zapta said in No 3.3V or 5V power with Vin, but...:

    If I read the schematic correctly, the blue led is connected before the VIN fuse so theoretically the fuse can be blown and the blue light will still be on.

    https://github.com/T3P3/Duet/blob/master/Duet2/Duet2v1.04/DuetWifi_Schematic_v1.04.pdf

    I will also check this out later today or tomorrow.

    Thanks for the suggestions everyone.



  • I was reading through M122 output and noticed that Vin is only 1.4V...

    Seems like this could be the problem...

    I currently have it wired with two 24V PSUs according the the duet guide found here. I checked and double checked that I had this connected correctly but clearly there is an issue with my approach.

    While dual PSUs is clearly supported, is this a recommended approach? The reason I am using it is my max power draw is right around 700W (350W 24Vdc bed heater, 50W heater block with the intent to do a second 50W heater for dual extrusion, plus 5 stepper motors) and 750W PSUs didn't provide much overhead, but 1000W 24V Mean Well PSUs were almost $250. I'm thinking it may be easier to just suck up that cost now and go for the single PSU approach.



  • How did you compute the total wattage of the 5 steppers? It seems too high if it brings you to 700w.



  • @zapta

    @zapta said in No 3.3V or 5V power with Vin, but...:

    How did you compute the total wattage of the 5 steppers? It seems too high if it brings you to 700w.

    You were right about my power estimate. Not sure what exactly I did before, but I checked the Duet documentation for PSU requirement estimating and I ended up with a much more reasonable total power requirement of 515W.

    Even in I go for a generous 25% oversized unit I could use a 650W PSU. Thanks for pointing that out.


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