Motors lose steps when heater is on

  • hello,

    for some days, I am unable to use my CORE XY C-Bot anymore. I experience huge voltage drops from 12V nominal to 9V or even 8V, with alarms appearing on the console. The power supply has been changed to no avail. My bed is powered by the main, so the only current sinks are the 5 motors (X, Y, 2x Z & E) and the hotend (12v E3D v6), plus a fan and a led strip that currently stay off.
    The last days here where very hot and I noticed that before the problem arose, the board temperature sensor went to 50°C. Immediately removed the board cover but the problem is still here even if the temp is now reported to be 32°C in operation.

    I am at a loss to fix that. I don't know if the board is suddendly faulty or if the hotend needs to be changed.

    What can I check to assess the problem ?

    Thank you

  • administrators

    Check that the screws in the VIN terminal block are still tight, and that the ferrules/wires going into them are not charred.

  • Thank you David.

    Do you think it's fixable ? I didn't really realized it was so severe. It looks like the connector is affected and maybe a capacitor according to the fine white powder around.




  • administrators

    The VIN terminal block can be replaced, but it will need quite a powerful soldering iron to desolder the old one because of the amount of copper connected to those pins on the PCB.

    Alternatively, as it is the + terminal that is charred and VIN+ is connected to bed heater+, you could connect the positive wire from the PSU to the bed heater + terminal instead of to the charred terminal.

  • Do you have the reference for the connector and where I can buy a replacement ?

  • administrators

    The part number isn't critical. Look for a 2-way terminal block with 6.35mm pitch and 32A rated current. These are available from the usual electronic component distributors and also on eBay.

    EDIT: the actual part number we use is listed at

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