I have an Arduino UNO R3. I was working on this excercise and I could not get the servo working. I thought the USB port may not provide enough power, so I plugged a 9V/1A adapter into the barrel jack as well. I also pressed the reset button. I noticed the edge of the PCB between the USB port and the barrel jack getting hot, and I unplugged the Arduino.

When I plug the USB cable in now, the "L" and "ON" LEDs light up, but there is no activity on the RX/TX LEDs and my computer does not recognize the Arduino (no /dev/ttyACM0 shows up). Looking at the edge of the PCB, I see a bit of a white powdery residue where it was heating up, although I am not sure if that was there before.

I'm worried that I may have burned something out in the PCB. I may have had the 3 pin header for the servo misaligned. Can anyone offer me some insight into what may have happened?

EDIT: Here is the edge of the board:


Sorry, I've already scraped off a bit of the powdery stuff, so it is harder to see now.

  • \$\begingroup\$ What do you mean the edge of the PCB? Can you show a picture of your board? \$\endgroup\$ Sep 28, 2013 at 19:27
  • 2
    \$\begingroup\$ If you cooked something it is likely the fuse, a trace, or a the regulator so potentially fixable. Next time don't try to power a servo or other motor through the arduino, but rather use a separate supply for motors vs logic. \$\endgroup\$ Sep 28, 2013 at 19:33
  • \$\begingroup\$ The board as a PTC, which should have helped somewhat but might need replacement. \$\endgroup\$ Sep 28, 2013 at 19:34
  • \$\begingroup\$ Gustavo, what is a PTC? \$\endgroup\$
    – ajduff574
    Sep 28, 2013 at 19:37
  • \$\begingroup\$ Also, the Arduino does still power on over USB, it just no longer presents an interface to the computer (if that makes sense). \$\endgroup\$
    – ajduff574
    Sep 28, 2013 at 19:42

1 Answer 1


It might be possible that you fried the fuse or the regulator on it. To verify that you can use a multimeter. There is a regulator which looks like this:

enter image description here

You can see if the pins are short(which means it might be busted). You should never power a servo as mentioned above by Chris, as it can draw too much current. If the regulator is fried, you should give it a shot to replace it, instead of spending money for another one. ALso try connecting it to another laptop to see if it is detectable.

  • \$\begingroup\$ If I fried the regulator, would the Arduino still turn on? It seems to work normally in every way except that it can no longer be programmed by my computer. I have also tried another laptop with the same results. \$\endgroup\$
    – ajduff574
    Sep 28, 2013 at 19:48
  • \$\begingroup\$ To Check if the Regulator is fried, take a multimeter, and see what output voltage you get GND and Vout. You can see the datasheet of that regulator here: pdf1.alldatasheet.com/datasheet-pdf/view/12048/ONSEMI/… . If you are getting a 5V output, then it might be your current surge protector. Since you see the led turning on it might be something else. \$\endgroup\$
    – Sherby
    Sep 28, 2013 at 19:55
  • \$\begingroup\$ @ajduff574: Just buy a few parts and fix it. It can't be programmed so its not that useful \$\endgroup\$ Sep 28, 2013 at 19:57
  • \$\begingroup\$ But before that, definitely know what part is not working. \$\endgroup\$
    – Sherby
    Sep 28, 2013 at 19:58
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    \$\begingroup\$ I don't believe that regulator is involved when the arduino is powered from USB. \$\endgroup\$ Sep 28, 2013 at 20:03

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