My first experience with Arduino ended in a tragedy. I bought a Leonardo from ebay and upon arrival, attached it to my laptop. Programmed a simple blink demo with the onboard LED. It started working. Then detached it from USB and plugged in a 9v adapter. The board started smoking and it doesn't work anymore. I measured the voltage of the adapter and it reads 9.7v. So, what is the reason of this tragedy?
I think that the smoke was from a component close to the processor. Right now, when I attach a 9v battery to the board, both the ON LED and the L LED remains on. The processor also warm.