E0 always on



  • I have a strange problem with my duet 0.8.5 running 1.18 dc42 fork. The e0 is permanently on from the moment the board is powered on. This issue seemed to occur after messing with the source voltage (changing 12v to 24v and back) as well as erasing and reflashing the firmware (i managed to heat up the hotend and stop the heating fine before that). The weird part is that the e0 is on regardless of whether the SD card is in or not which makes me think that it is a wiring problem independent of the gcode. The e0 LED is also permanently on. I have tried to reflashing the firmware again and changing the Vin to 24V and back as well as changing the config.g (very new to gcode so probably didn't make a difference).

    Can someone advise me if this is a software/hardware fault and how i would go on about resolving it? At the moment I've changed the gcode so that I can use the second extruder but it's a messy solution as i have to set the temperature of the first one to heat it (using paneldue).


  • administrators

    If you disconnect the E0 heater wiring from the Duet, does the E0 led still stay on?

    Are you certain that the back of the board isn't shorting against anything?

    If the answers to the above are yes and yes then it sounds like a fault on the board, which could be diagnosed using a multimeter.



  • @dc42:

    If you disconnect the E0 heater wiring from the Duet, does the E0 led still stay on?

    Are you certain that the back of the board isn't shorting against anything?

    If the answers to the above are yes and yes then it sounds like a fault on the board, which could be diagnosed using a multimeter.

    I've disconnected everything from the board and taken the board of the mount and it still has the same issue. Could you help me diagnose it? I have a basic multimeter. Thanks

    Edit Quote Answer Delete Report


  • administrators

    I suggest you measure the voltage at the gate and at the drain of TR3. The part number for TR3 is BSH105. With the heater commanded off, the gate should be at +3.3V and the drain should be at 0V.

    • If that's how they are, then TR4 (the main E0 mosfet) is shorted

    • if TR3 gate is at 0V then either TR3 or the microcontroller is faulty, or the firmware is turning the heater pin on. Check that you don't have a M307 H1 A-1 C-1 D-1 command in config.g to free up the pin for another purpose.

    • if TR3 gate is at +3.3V but TR3 drain is at 5V instead of 0V, then TR3 is faulty.


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