arduino uno R3 green (made in italy)

Hi all Can you please tell me if i can purchase the Atmege16U2-mu(R) and where? I have found Atmega16U2-AU at RS Electronics and if this compatible to replace the chip on my R3, I have 3 boards that are blown and cannot connect to my computer. Computer does not see them. Every time i must buy another R3 and they are not cheap as repair is my best option. If I can use the U2-AU chip is it just a matter of fitting them or is their more involved. The cause of blowing the boards is accidentally applying 12v instead of 5v to the boards. Thanking you for feedback in advance. John

First of all, are you sure with damaged ATmega16U2? It is not -AU but -MU, it is different package - QFN32. Provide a photo or link to be sure because it can differ if it is not genuine Arduino. The second thing is that it is not so easy to replace. Rework soldering station is needed. And finally, there is firmware loaded in ATmega16U2 so some programmer or another working Arduino is needed for upload via ISP. You can buy ATmega16U2-MU in each shop for electronic components also on the internet. I don't see a problem with chip purchasing but I am not sure if it worth.

Hi. Here is the link to the Atmeg16AU chip i can get from RS Electrinics.

http://za.rs-online.com/web/p/microcontrollers/8149100/

Why could the developers not just place a 5.1V zener across the power in, to offer some sort of protection to the Arduino? or am I stupid?

The link you've posted is to ATmega16M1-AU. It is wrong MCU type. I thought link or picture of your Arduino if it is not original because non original Arduinos can differ.

Arduino has diode on barrel jack input which protects against changed polarity and 5V regulator has built in protections but accepts 12V on input. If you applied 12V directly to +5V pin you bypass everything and probably not only 16U2 is damaged.