I have had my Arduino Uno for many years now, and it continued to work until just recently. I had it connected to both my computer via USB and a 12V wall wart at the same time (which I read is safe). After a little bit of using it this way, it stopped working as it's supposed to. When I try uploading a program, I get the following error:
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x00
I think what happened is that I must have put more than 5 volts into one of the analog input pins. The lights are still on when it's plugged in via USB, and it works as a 5-volt power supply, but not as a microcontroller. Can I just replace the ATMEGA238P-PV, and it will work again? From looking at the PCB design, it appears that the analog input pins are directly connected to this chip, and not anything else on the board.
You can try replacing the ATmega328 chip, but it is possible that the USB chip was also damaged. If the ATmega328 chip is socketed, take it out and see if the board is recognized by the PC (that is, a COM port appears).
In response to @jremington , I would recommend replacing the chip first as the USB port can most likely handle up to 15V with no issue. If the chip IS fried, as is most likely since you said it still worked as a power module, there are many cheap replacement microchips available for less than $3 like the one listed below:
You can try loopback test to find out if the rest of the board is working properly. Just remove chip before the test.
ATMEGA238P-PV you probably mean ATmega328P-PU. 328P will need the bootloader. You can buy it with the bootloader uploaded in some shop specialized for Arduino or you can upload it by yourself.
All info about loopback test and bootloader uploading is here on the forum and arduino.cc.
You are wasting time and money trying to repair a uno.
Why not take the opportunity to buy a more modern and powerful "arduino"
such as a nano or micro - that are cheap as chips?
or a NodeMCU or ESP32 module?
Nowadays almost everything around hobby electronics is "waste of time and money" if you can buy final product.
I would take this as opportunity to learn something.
Same. If this guy learns nothing and buys another arduino, there's a higher chance of him frying it again because he didn't take the time to learn how to fix it the first time.
Not knowing your skill set or tool box I would say the best is to replace it and frame the old one and label it old reliable as it has lasted through many iterations. The parts to repair it will cost more then the replacement.