Arduino Uno not working

Hello!
I was constructing the lightmusic using this plan.

I applied 12V from the power supply and connected the board to PC in order to see the Serial data, but I got an error saying that the COM port wasn't found.
I disconnected all the cables from Arduino. After that it doesn't appear on the PC by any means, COM port doesn't appear in the IDE. I tried using other USB ports but there was no result. However, after connecting Mega, everything started to work again. Tell me please, did I "burn" Arduino Uno completely?

did I "burn" Arduino Uno completely?

Well maybe not completely but perhaps just the processor that does the USB to serial conversion.

Grumpy_Mike:
Well maybe not completely but perhaps just the processor that does the USB to serial conversion.

That is, can throw away and buy a new one?

Suggestion: throw away the Uno and buy a new Uno.

In theory, you can replace "just the processor that does the USB to serial conversion" but:

  1. You have to be good at desoldering and soldering surface mount devices, AND
  2. It is an assumption that the only thing "burned" is the processor that does the USB to serial conversion.

Good Luck!