Arduino UNO won't power on via USB

Hi I just got my Arduino UNO. When I plug in via USB, the board doesn't light up the power LED green and doesn't show up under the PORT>

Any idea why? If I power via a daughter board and 3.7v battery it does..

It could be caused by several things and it is little bit advanced for skills. Look at the schematics. Fuse on USB power input. It is reversible fuse so some problem (short circuit, overloading...) persists or the fuse is damaged. Next is MOSFET for switching between USB and jack power. Maybe it has gone or there is switching voltage problem from comparator. It compares 3.3V from onboard regulator against to Vin. With the multimeter would be able to detect problematic part.
What is a daughter board and how is the battery connected? Please be more specific.

Let's start at the beginning.

Have you tested the USB port on some other device?
Have you removed all other connections?
Have you done any voltage checks?


Did you try another USB cable?

It turns out that the board had a hardware mod from the class i am attending.. I think they removed the FET.

Only reason for that I can think of is they wanted to power the Uno with 5V (Uno is bad at that...) But yeay, without mosfet, no power.

Same happened to me on Arduino due. I had connected to my xbee and it wont power on when connected via USB but will power on if I use separate battery source. then I removed my xbee. Then it worked after that I connected my xbee !! Wierd

try adding arduino LLC FROM Device Manager/Action/Add Legacy...

Works for me...Had the same problem...