Burned component on Nano

Hi all,

I was experimenting with a PAM8403 and an 8-ohm speaker when my laptop stopped recognizing my Nano. After inspecting the board I suspect this got component got burned (bottom board): |500x281

About this component: - It's entirely black with 3 vertical lines 'engraved' on the left - The surface of this component got a little teared up making the marking partially unreadable, with the ending "2" still visible.

Before the nano stopped working: - Nano kept self resetting while plugged into laptop's usb, perhaps this is a sign it was pulling too much current?

This is the current situation: - PC doesn't recognize Nano (no plug-in sound by windows, can't select Port in Arduino IDE) - When plugged in to power with usb, 5V-GND reads only 2,6V - When using batteries to power the nano (VIN), steady 5V from 5V pin, so voltage regulator is OK. - Using an USBasp I can successfully upload sketch Blink

Considering all of above I suspect the burnt component belongs to the USB part of the nano. After reading this site I'm thinking it's a diode but there seems to be no diodes at the USB according to the nano v3 schematic.

Does anyone know what component this is? I'm hoping to replace the part myself. Thank you for your time.

Yes, diode. Here is an Instructable with info about that board layout and components, and it also includes a link to yet more info and schematic provided by forum member marpik: http://www.instructables.com/id/Arduino-Nano-ATmega238PCH340G-v30-PCB-layout/

Thanks for the link, so it seems to be a Schottky after all. Could I replace it with any smd schottky?

The official Nano schematic on this site (arduino.cc) shows it uses MBR0520 which is a 0.5A rated diode, so perhaps it would be best to stick with something with a similar rating. Marpik's schematic of the Chinese Nano shows the diode is SD101CWS, and that one is rated for 30mA, so I'm thinking that was a mistake on his schematic. My Chinese Nano has the marking B2; I'm thinking it is a diode in the MBR0520 family. Go for a Schottky Barrier Rectifier or Schottky Power Rectifier with 0.5A current rating.

You can also just remove the diode and leave it off, and power the Nano with regulated 5V on the 5V pin or 6 to 9V on the VIN pin, during programming via USB.

Or program it via ISP and don't use USB at all. If you remove the RX and TX resistors and remove the DTR capacitor, the board will essentially become an Arduino Mini clone.

I have a Pro Mini lying around as well but the usb is just too convenient without all the extra wiring :)

Would SS34 be a good substitute? It's rated 3A and the Vf seems to be comparable with the MBR0520.

I think so, if you have it on hand. I am not an engineer. But I'm not sure it will fit well, seems too big. You may need to do some trick with a piece of jumper wire. These Nanos are not worth spending money on to repair, because the whole thing is so cheap. When I have a problem with one of them, I throw it in a bag marked boneyard, and sometimes scavenge parts off of various boards to make another whole working one.