Moved printer, attempting print damaged board, blew another

  • I am not quite sure what happened. I am running a Duet 2 Maestro. My printer has been running flawlessly on 20hr prints for weeks. I moved it to another location, and after attempting a single print, the print would freeze after the first layer and my bed would not stop heating up. The bed heat light would turn on as soon as I power on my printer and stay on even with the SD card removed.

    I switched to a backup duet 2 maestro and it looked good when I powered up. When I tried another print, the same thing occurred. While troubleshooting, I attempted a different print file, which blew a chip on the board. No idea what changed that could cause such an issue!0_1559270124625_20190530_212441.jpg

  • I should also mention that nothing appears obviously shorted or damaged elsewhere on the printer.

  • From the photo, it looks like you're running the board naked on some kind of surface with some words running on the underside ... The stepper drivers require airflow for cooling on the underside and there might be enough heat to affect the cables. Both combined can lead to shorts across the solder points on the underside of the board. At that point, all bets are off, especially if you happen to cross voltages (the board has different parts running 3.3v, 5v, and your input voltage -- either 12 or 24v).

  • The board is on standoffs and the first one did not have the wires going behind, that was just a quick thing that happened for the second board. The stepper drivers have ran fine like this for months, and the second board blew in minutes. I double checked the wires behind the board and they are undamaged, and not creating any contacts that could short.

  • @bass4aj Looks like U3 has blown.

  • @stephen6309 What does U3 control, and what could cause it to blow? I have yet to test it, but I am wondering if maybe there is a short in the PCB bed? there is no visible burning or damage, but I did notice it was heating unevenly before I blew the board.

  • If it occurred twice with 2 boards that would indicate there is some fault with your hardware. Problem happens when you are trying to print, so lets narrow it down to heaters.

  • @arkadiusz good idea. do you know what I should look for with a multimeter? I agree its likely hardware but I am not sure how/what to look at.

  • check the resistance of the heater.
    then check the resistance of between the heater and the thermistor.

    do this with the bed and hotend.

    there should be a little bit of resistance for the heater and no resistance between heater and thermistor.
    do wiggle the wires while testing.

  • @veti resistance between heater and thermistor? The heater is a pcb bed and the thermistor is a cartridge style pt1000 attached by Kapton tape. Or are they linked through the board somehow?

  • they should not, but the there could be a short on the hotend. when you power the hotend that would send vin to the thermistor connector.

  • @veti Ah gotcha. I will get those checked and post back. Thanks

  • administrators

    What PSU are you using, and have you checked that it is outputting the correct voltage? Over-voltage at the input could cause U3 to fail.

  • @veti there is no resistance between either heater/thermistor. Both heaters have some resistance. Looks normal. @dc42 Its some generic supply that M3D put on the Promega printer. Its a 24V supply. DWC reads a constant 23.7V or so, and a check with the multimeter (after detaching from the board) shows 24.1V.

  • @dc42 I also just confirmed, its not U3 that blew. L2 blew. I was touching it with a pick and the whole part just fell off lol

  • @dc42, what kind of things could cause L2 to fail? I should also mention I saw a different thread in the forum with a similar bed issue (but not quite the same). In that post, you suggested to disconnect the bed ground and tape it to the frame. On the first board when I did that, the bed heat light stayed on, but the bed stopped heating up on start-up if that helps.

  • administrators

    L2 masy blow if either U3, C6 or C12 fails. Unless C6 or C12 looks damaged, my guess is U3.

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