Duet 2 Wifi - Only the Vin LED is lit

  • Configured as a 3-axis CNC, housed in a PVC utility box with two fans, and a filter on the intake. It has around 140 hours of milling on it. I shut it off on Thursday, now it won't power up. Only the Vin (24.16VDC) LED is lit, PanelDue 7i stays dark.

    Removing the board, plugging it into USB, only the Diag LED lights (dimly), and R23 (I think) gets very very hot. My fingers are too low-tech to say with confidence that the frying pork smell is coming from R23, but I think that's the one.

    Is there a common area to check first? A known weak link, like an underrated linear regulator, etc? There's probably a schematic for this somewhere, so maybe some nice person can share a link.

  • Moderator

    @Giblte535 said in Duet 2 Wifi - Only the Vin LED is lit:

    There's probably a schematic for this somewhere, so maybe some nice person can share a link.


    Photo of the board? Maybe we can spot a burnt up component. If no other LEDs are getting lit when connected to USB that's not a great sign, but try working through this to see how far you get.


  • Thanks for the schematic!

    My vision isn't that great, but I stuck it under a scope. Ahh HA!

    U3 appears to have a volcanic vent obscuring the label. I'll have to dig through the schematic to find out what U3 is, and what might cause it to fry like this. It looks to have done some smoking too, but there was none of the usual magic smoke aroma...


  • Moderator

    How old is the Duet? When and where was it purchased?

    U3 is the 5v regulator and has been known to melt down from time to time.

  • @Phaedrux Purchased from Filastruder in March of '19, but not put into service until March of '20.

    This A4403 buck converter is rated for 3 amps. That seems a little lightweight for all the 5V systems on this board. Is that really enough to power the PanelDue 7i, plus all the other 5V logic, plus the 3.3V drain of the controllers?

    A replacement is $1.78 from Digikey, and some nightmarish hot air work down in a deep, dark parts canyon.

    Maybe 1.10 could replace U3 with a bank of socketed T03 7805's on a big aluminum heat sink. 😐

    With thumb screws.

  • Looks like the 1.04 boards add a fuse to the A4403 supply circuit. Or, at least the circuit is powered from a fused supply.

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