Bringing a UNO R2 back from the dead.

I recently tried a buck convertor using arduino, which ended up sending a 12v dc to the A2 Pin from a lead acid battery, through a potential divider.

I assumed that port gone,so replaced the atmega 328p with another with arduino boot loader .But the UNO is still not working.

Can any one tell me how to solve this issue.I have some emotional attachment towards this board. I want to fix it.

My hardware is UNO R2, original board from Italy.