Arduino Nano clone does not power up via USB anymore

My Arduino Nano clone initially was booting from USB and recognized by the arduino IDE. I mounted it on a breadboard, made a circuit with a led and a resistor and uploaded a sketch. Since the program didn't work as expected (to blink the led) I kept trying new things (either changing the program or tweaking the IDE) and then suddenly it powered off and wouldn't boot anymore (all lights off, even reconnecting usb and pressing reset). I'm not sure what happened but maybe I overwrote the bootloader. I bought another usb cable but nothing, still dead.

I then verified that the nano still boots from external power source, but even with external power I keep getting "unable to enumerate USB device on port 1". I then read that pre-2009 nanos have a problem that requires shorting two pins on the USB chip; but I'm not sure if this applies to me since mine is revision 3 (with atmega328) and it is an arduino-compatible clone.

Or actually. The salesman said it's revision 3 but maybe it actually had an atmega168 and that's why my program didn't work.

But anyway, usb isn't working at all - when I connect the usb cable, there is nothing at the "5V" and "3.3V" pins.

Could my problem be bootloader-related? The odd thing would be, I think that even without bootloader it should receive power from usb. And, the other odd thing is that when I power from Vin, it doesn't light only the power led; it also blinks a red and a green led, and only bootloader-capable arduinos should do that.

Also, does this description seem to be consistent with the pre-2009 usb chip failure? If unclear, what could I do to investigate this? (ps: I don't know any soldering)

And finally, Is it likely that I can still program the nano with another arduino?

I am waiting a leonardo (this time original..) and maybe I could use it to program the nano.

I don't think you quite understand what the bootloader does. All it does it assist in loading new code from the PC. It has absolutely no control over the board's power or the power LED.

Okay, thank you.

I'm wondering why there is no voltage on the 5V pin when I plug the USB. The schematics point that it is regulated by a MBR0520 Schottky diode. Hmm, apparently someone had a similar problem..

Two more questions:

  • Where is the "polyfuse" in the board?
  • If just this component (MBR0520) died, would USB stop working when I power via Vin? Could maybe the problem be on the FT232RL chip instead?

Wow, I manually shorted the two pins of the MBR0520 and plugged to the USB and the lights were up again!

I suppose I will have to learn soldering.