I recently purchased an Arduino Uno. I've been having a ton of fun fiddling with it -- that is until I pushed +12V to the Vin without any kind of voltage step-down. The smoke was violently released from the Atmega chip and the chip socket itself even melted somewhat.
I purchased a replacement ATMega328P-PU for the unit which was pre-loaded with the Arduino firmware, however when I energize the board from the USB port the status LED stays a solid orange rather than the fast-3-blinks that indicates the firmware is ready. I'm not sure if this is a case of "the chip really wasn't loaded with the Uno bootblock" or if there's another component on my Arduino board that is fried.
I have access to a multimeter and a 10MHz oscilloscope, can anyone give me some ideas on how I can diagnose where the fault may be?