Why did I blew up my pc?

Hi every one.

As in my subject I blame myself for destroying my pc , but why did it happen.

I got my Arduino nano plugged in to the pc via the USB cable.

Then I connect my 12V supply to Vin , the amps shot up to around 2A then my pc switched to a light blue screen and printed "LOCKING" never came back on.

I suspect that one of the small FET supplies in the pc blew but I cant see anything burnt or any of the FETS
test short.

So why did the Amps go so high ?

Thanks for any reply.


'Then I connect my 12V supply to Vin'...would that be the 5 volt 'Vin' pin?


The Vin pin is marked on the Nano pcb so is the 5V pin , I did say I used the Vin PIN .

You have no clue anyway.

Just pushing up the Post count.

You have no clue anyway.

Just pushing up the Post count.


I may have no clue but I didn't just 'blew up my PC'.

It was a valid question as it's easy to get the pins confused with the writing so small.


I may have no clue but I didn't just 'blew up my PC'.

My thoughts exactly; not blewing up your pc trumps blewing it up, any day.

The nano with nothing else connected ( except the usb) would work fine when a 12v DC supply Is connected between Vin and Ov.

For it to destruct , you must have wired something wrong !

Never seen a PC screen say “ locking” - you sure it won’t restart ?

Hi Hammy.

The LOCKING of a pc is well documented in google , normally a hardware failure , no tried every thing suggested

from many google searches and pc does not switch on.

I have used many Nano's with an external 12V supply on Vin.

For the last week I used this specific nano with a red and black wire connected to Vin (red) and black (gnd), I

always put a 1n4007 diode in series in the positive feed line to prevent accidental reverse polarity.

I always disconnect the PSU then plug in the USB and program..but this one time I made a mistake and

had both PSU and USB connected.

There is a few posts on the internet where this also happen to other people but they blue up their Mega

and not their pc.

Hi, mikedb!

You did not provide the essential information like:

  1. Is your Nano still operational?
  2. Is the USB cable still operational?
  3. What max current your power supply is rated for? Does it have overcurrent protection?

So far my guess is that the voltage regulator circuit in your Nano was shorted and 12V power got to your PC USB and burned it. I guess that your PC USB is short circuited now, and that's why PC is not able to reboot.
I ask you about your power supply because I wonder why 2A.


Nano is still fine uploaded BLINK.

Obvious USB cable is also fine.

Power from USB ok…Disconnect USB… External power 12V on Vin also fine.(read 5.02V on 5Vpin)

Yes power supply is 0 to 30V and 0 to 3A.

Current was limited to + - 2A.


Ok, at least it explains 2A current surge. But let's try to think logically. We know that the power from the power supply somehow got to PC and fried it. The question is how? Because the Nano is still functional it should be some path to bypass it. And this path exist in small boards like Nano and Micro - the ground path. In Nano and Micro (not sure about other small boards) the board ground connected to Mirco(Mini) USB cases (unlike bigger boards like UNO and Mega). I advise you to check if on your USB cable cases of USB connectors on opposite sides of the cable are connected (on some cables they are connected, on some cables they are not). If they are in your case, it is possible that because negative power terminals on PC USB and on your Power Supply are at different potentials with respect to ground (floating voltages) the discharge of the output capacitor on your Power Supply could fry your PC USB port but did not affect your Nano. Just a possibility! By the way, I myself had fried just a few Megas when connecting external power and USB simultaneously!