UNO R3 Internal 5V Power Short Circuit

Hi,

I was using my Arduino UNO R3 from last few months, until one day i saw my Power Regulator AMS1117 5V was burned. I replaced with another AMS1117 5V and the same. Now i removed AMS1117 and when i measure 7 & 8 Number pin with Continuity tested i am getting short circuit between VCC and GND of Atmega328.

What could be wrong ? there were no modification made to original circuit. Which part is parallel to 5V Regulated output which can cause short circuit ?

Anyone has such experience in past ? please guide me which part should i desolder and check ?

Probably easier to buy a new one but there is a 100nF cap across these two pins

Edit: Wait, you mean Arduino pin 7 and 8? Or physical pins 7 and 8? Physical pins 7 and 8 are the Vcc and Gnd pins, so one should be connected to Vcc and the other to Gnd.

Often when people start replacing parts to fix Arduino’s that have been damaged like this, they wind up doing damage in many places. Probably the power supply switching opamp is blown, that normally fails to near short across power rails, and if it’s an official board, the 16u2 serial chip is probably blown too (and that one is very hard to replace) - on the clones with other serial chips, it’s more likely to still work.
I generally recommend just replacing boards after something like this happens to them.

What was connected to those pins? It sounds like you inflicted some serious abuse on those pins!

asking:
Hi,

I was using my Arduino UNO R3 from last few months, until one day i saw my Power Regulator AMS1117 5V was burned. I replaced with another AMS1117 5V and the same. Now i removed AMS1117 and when i measure 7 & 8 Number pin with Continuity tested i am getting short circuit between VCC and GND of Atmega328.

What could be wrong ? there were no modification made to original circuit. Which part is parallel to 5V Regulated output which can cause short circuit ?

Anyone has such experience in past ? please guide me which part should i desolder and check ?

it is not at all clear where you are taking your measurements.
Taking continuity reading on a PCB are very difficult.
With the Atmega328 installed the continuity readings are meaningless.

to short out the 5 volt regulator would have to be something in series with the output of the regulator.
The 5v regulators have thermal shutdown protection so that they do not burn up.

Did one of the capacitors on the output of the 5v regulator fail?
normally they fail open.

Can you post a photograph of the top of Arduino UNO?