Arduino yun overheating SO19B


I’ve an Arduino YUN. As i connect it to a USB cable, the S019B on it quickly heats up. So hot that touching almost burnt my finger. I tried looking for this part on the schematic but couldn’t find it. Googling it lead me to datasheet of a “LM3668 1-A, High-Efficiency Dual-Mode Single-Inductor Buck-Boost DC-DC Converter”
What part is it?
What could be the reason for the overheating and
what is the possible solution.

P.S. The Arduino YUN is not detected on the PC (MAC). I’ve another YUN that’s working perfectly fine with same USB cable / PC. Attached is the image of the part.


Having this moved to the YUN section..

Did you do any recent painting near the YUN ? (just going by the picture)

Hi, The one in picture (with the spray paint) is working. The other YUN which I have is giving the problem.

Hmmm I had a think about this but would like a little more detail if you could..

What have you had connected to it and HOW... a schematic would be really nice even if its hand drawn.
What have you been using to power it Voltage / pins used etc.

If you have SMD ability and decent test equipment you could try replacing it but if not you may be in for a quite hard task.

The Arduino YUN is powered with USB connected to my macbook.

There's a buzzer connected to pin 8. (Buzzer Red to 8, Black to GND)

There's a Relay board, it has a separate power source. It uses pin 9 of Arduino, and a common ground connected to Arduino GND

And there's a Seeedstudio NFC shield (V2) stacked on top of YUN.

The yun is powered only through the micro USB connector. Only the NFC shield and buzzer draws power from it. The relay is given a separate power supply.

Replacing on own looks a little tough. I might damage other parts in the process. Also the faulty part has to be available.

Can you please tell me what's this part (s019B) doing on the board ? I could not find it on the schematic files.