Sometimes you may do something stupid, other times it is totally inexplicable but as a result of whatever events, the green power light on your Arduino stopped coming on. In my case it turned out to be a burned out voltage regulator.
This inscrutable is a explanation on how to replace it and identify the problem. I couldnt find anything online that explained how to fix a dead Arduino so this may help some people.
(keep in mind that your Arduino could have something else fried, so this wont work in every case)
But also this may work on a regular arduino, if in fact you did burn out the voltage regulator, since they both use the same part.
Step 1: Looking for the problem
When plugged in, the big overcurrent inductor (in the image below) on the board would quickly heat up, the board wasn’t recognized by the pc and no lights came on.
After thinking what could possible be wrong, the voltage regulator came to mind. It takes whatever voltages go into the power supply and brings it down to 5 volts that is needed for the ATmega chip. The regulator on the board is the: MC33269D-5.0
Go here for the datasheet:http://pdf1.alldatasheet.com/datasheet-pdf/view/12048/ONSEMI/MC33269D-5.0.html
it comes in two packages that do the same thing but look a little different, your arduino may have either one.