Genuine Uno R3 - problem with 16U2 MCU ?

Using Arduino Avrdude, stk500, Bootloader issues
1

Hope this is the right place to ask about this.

I have had this Uno R3 for a few years and it worked fine until recently - though I can't remember now when the problem actually arose.

Now when I plug it into my Linux laptop with the regular USB cable it does not appear - it's as if nothing is connected. The cable works with other Arduinos and when I tried a different cable with the faulty Uno it did not work either. So I don't think it is a cable problem. Though I guess it may be a fault in the Uno's USB socket - although everything looks normal.

I am able to upload a program to the Uno using a USB-TTL cable connected to Rx Tx and GND so clearly the Atmega 328 is working fine.

So it seems as if the 16U2 has gone on strike.

Are there any diagnostic tests I can run to check out the 16U2, or maybe someone has experienced this themselves and can offer a solution.

...R

2

It can be 16U2 or something around like burned ferrite bead. You can check some things with just simple DMM. First of all check the voltages.
Power circuit, works on USB cable? 328P?
You can check the oscillator on 16U2. It should be seemingly DC voltage approximately VCC/2.
Eventual replacement is not easy. You will need hot air and there is high risk of damaging plastic headers.