OOPS!
Hooked up a 12v power supply to the 5v out pin and now it seems to be fried. TX/RX/L/ON LED's are steady on and does not do anything else. Computer doesnt show a USB connection either. Is this fixable? I could probably replace the SMD voltage regulator if anyone thinks its worth the trouble.
What I meant to do was power the arduino off a breadboard thru the VIN pin but forgot to switch it over from powering the breadboard off the 5v pin.
Could very well have destroyed the microcontrollers, both the main ATmega328P and the ATmega8U2 that does the USB-to-serial conversion. The former can be easily replaced assuming you have the DIP package. The latter will likely require a hot-air rework station, then the new chip will need to be programmed, etc. And of course other things might be dead as well.
Might be best to chalk it up to experience and get a new Uno. I might keep the old one around just in case I got bored on a rainy day or something.
Thanks. I figured it was probably beyond repair.
I noticed something interesting that supports your theory. I tried installing the AtMega on a breadboard and hooking up an LCD to try to run the sketch that was already loaded. Nothing.
I then tried to power an LED off the 5v pin and it works, along with the 3.3v. This works with both the power jack and USB, but the TX/RX LED's stay on when plugged into USB.
Could be that the regulator and other power supply components are still operational, or at least mostly so. They might be more tolerant to an over-voltage event.