I have problem when i connect my Arduino UNO r3 I got the message"usb device not recornized". I tried
1.change usb cable
2.install driver in folder drivers(not work)
3. Press reset button
4. Change Pc
5.Change OS-use ubuntu(have same problem)
6.Change IDE
Before problem my arduino dropped from a height of 20 sm.Led power work. Сan be the cause of the crystal oscillator? 