My leonardo was working fine until today, when I plug it to my computer all led (RX/TX/L/ON) stays on (Green for on, amber for others) and my computer no longer see a com port. (by the way, do you know what the L led mean ?) If I add external power, TX goes off then after few seconds RX goes off too then back on. With external power, the atmega goes very hot (I can't touch it). RESET button do nothing.

Is my Leonardo dead ? Any idea what could have cause that ? The fact that the atmega is so hot when the board is powered up with 12V let me think that the voltage regulators is no longer working. Good guess ?

1 Answer 1


By your description, I'd say:

Quite Probably.

You should check what the 5V and 3.3V voltages are using a DMM.

  • Confirmed, i have 12V on 5V pin when I put external power. I guess it would be safer to have something which can limit the input current on the external power supply. Any idea how I could do that ?
    – radius
    Commented Jun 2, 2015 at 21:35

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