I have an Arduino Duemilanove, and its 3 built in LEDs (rx, tx and L, the pin 13 LED) keep turned on everytime i power it up. The Serial chip right next to the USB heats up really fast, and pressing the Reset button has no effect. I cannot communicate to the board at all, because the Arduino IDE says it can't find the board at the COMPORT, and Windows' Device Manager does not recognize it.
The Arduino stopped working after I was using it with a 12VDC power source and the USB cable to my notebook. My computer was running on battery, and it run out of power. I'm not sure if this was the cause, but I just don't seem to be able to upload anything to the board anymore to test it.
Don't know if this is relevant, but I was trying to control a 12V DC Motor with a L298 H-Bridge and Arduino.
1,5A is enough to fry an Arduino? The power source was 12V / 18W
First a load such as a Arduino board determines how much current will be drawn from a DC power source, not the power source. One can wire a Arduino to a 12vdc power source (via the external power connector or the Vin pin only) rated at 1,000 amps but still only the current flow would be determined by the Arduino board and whatever external components you have wired to the Arduino. Ohms law states that current = voltage / resistance. The Arduino represents the resistance in this case.
A normal Arduino draws current on less then 100ma, plus any additional load you have wired to external devices if used. So an internal or external short circuit or miswiring could certainly cause high current draw from the power supply and damage components on the board, the how and what are hard to reconstruct.
So we don't have nearly enough information to speculate on what might have cause the damage to your board, but it's certainly not just caused by plugging in a 12vdc 1.5 amp power supply to the external power connector.
