I have an Arduino Due (made in Italy) which suddenly (after working nicely for some time) started a new behavior: If I connect it to my computer via USB it is recognized and connects. The "On"-led is turned on but gets darker within seconds until it's off and the connection breaks. This happens with both USB ports. The area around the usb ports gets hot and especially the "504L" next to the reset buttons. (I just have my finger to measure the temperature, so it could also be something else in this corner).

What could have happened to the board? And is there anything I can try to revive it?

Update: @GuitarPicker: It's the object labelled "0105" in your image, so it's probably the F1 fuse. If I connect the top USB, F1 gets hot, if I use the lower usb, F2 is activated.

  • There is nothing connected to the board. Before that, I used it to send SPI commands where I might have connected some of the SPI pins in the 6 pin group.

  • The board is placed on wood, so there should be no external connection

  • No smoke or visible damage.

  • I'm having trouble locating your "504L" part. One sheet says it's a tiny resistor about 1mm x 0.5mm Perhaps it's a different revision. Near the reset button, I see a resettable fuse (F1), and a pair of capacitors (C25, C27). Please check the layout below and see which part number corresponds to the hot one. I suspect it may be the fuse. Links: Layout, Schematic, Photo Commented Nov 20, 2015 at 14:20
  • The board is using too much current. This will trip the polyfuse, which will gradually increase resistance. Which explains the power led fading out. Is there anything connected to the board?
    – Gerben
    Commented Nov 20, 2015 at 14:25

1 Answer 1


The "504L" is a 500mA polyfuse. If more than 500mA is attempted to be drawn through the USB port it will get hot which causes the fuse to "trip". When it cools down again it will "reset".

Why is too much current being drawn through the USB port? Well, that's what needs answering to know just why your board is misbehaving:

  1. Do you have lots of things plugged into the board - like LED strips, motors, etc?
  2. Is the board sat on something metal causing a short circuit? (I did that by having some loose change on my desk once).
  3. Have you physically damaged the board and caused some pins of one of the chips to short together?
  4. Has the Magic Smoke™ escaped from one of the chips rendering your board broken?

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