Shorted Maestro

  • My cable on the heatbed broke. I came to completed print but LCD was blank. I switched printer of and on and moved the bed to get my prints of when i saw sparking on bed wires discovering they were broken. I switched it off and resoldered wires back on but the bed does not heat up. What could went on the maestro? How can i fix this, perhaps a burned mosfet ? Any way to diagnose with multimeter?

  • Most common failure mode of the mosfet is a short, so just measure continuity across the bed output when the board is off. if its a short when the board is unpowered then fet is fried.

  • @bearer great, thanks. Hopefully its nothing more and fets are easily available

  • administrators

    With the bed heater disconnected from the Maestro, if the bed heat LED does not light up when you command bed heat (before the firmware detects a heater fault and shuts off the heater), then it's likely that the mosfet has gone open circuit. Or if it it lights up even when you don't command bed heat, then the mosfet has failed short-circuit.

    In theory the mosfet can be replaced, but it's not easy because it's close to the VIN connector, and the PCB acts as a heatsink; so it's difficult to get the mosfet hot enough to remove without burning the VIN connector. If your E1 heater output is free then it might be easier to use that to drive an external mosfet board instead.

  • @dc42 Is it this one i marked?

    I do have some soldering skills so i might try that to save me extra wires. Could you share what mosfet to look for? Would appreciate the info as the text is tiny and i would probably not find the exact one

  • administrators

    Yes, that's the one. The part number is IPD036N04L. If you do attempt to remove it, here are some suggestions:

    • Use a few layers of Kapton tape to shield the VIN/bed heat connector and other components in the area from the hot air that you use to melt the solder under the mosfet

    • Put the board (or at least that corner of it) on a hotplate heated to around 125C. That will make it easier to desolder the mosfet. Remove the SD card first.

  • @dc42 thanks. Good advice. Will report back when done

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