It is the 2nd time that an Arduino UNO board is crashed. No upload is possible anymore between the IDE and the board, although many times before all went OK. Only the green LED is on and the yellow LED was flashing 3 times after plugging in the USB cable.
There is one circuit connected to the +5 V power pin of the Arduino UNO and it is drawing 30 mA.
During the upload a message in red appeared:
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x4a etc.
It has the right Com port number, baudrate setting etc.
During Upload the TX and RX leds of the board does not flash or are ON. They stay OFF.
On the first Arduino board that crashed I just could see a component around the RX/TX leds overheated. After that the same failure as described above for my second UNO.
I connected an Arduino NANO to the same USB cable and now uploading of the same sketch was no problem. During upload RX- and TX LEDs were flashing. So the communication with the pc and IDE is OK.
Sometimes when I do not need the Arduino, then I unplug the USB cable from the PC or plug in when needed again. I do not suppose that this action can cause overheating on the board.
I have done the loop-back test Instructions as posted here:
https://forum.arduino.cc/index.php?topic=553853.0
Sending "test com port" in the serial monitor returned "?;????⸮;⸮??⸮" at 9600 Baud. With other Baudrates nothing was returned.
With the tool "Board Info" I get the right info of the Board.
Perhaps somebody any idea?