My pc shorted out and now it doesn't boot up

Question

My PC was working fine. One day, I plugged in my USB printer and shorted out the PC.

I restarted and it worked until today. Now the PC won't turn on.

I tested the power supply on its own with a PSU tester and seems to work fine. I also installed a brand new power supply and nothing.

I have noticed that when I have the PSU plugged into the tester on its own, it works fine. As soon as I plug in the auxillary 2x2 pin on the MOBO, it shorts out.

Would appreciate any advice.

Solution

as soon as I plug in the auxillary 2x2 pin on the MOBO it shorts out.

This strongly suggests that the power regulation/conditioning circuitry for the CPU (that's what the aux connector is for) is "blown". The same circuitry may sometimes also be used to regulate/route USB power, which may have caused the problem.

Hopefully your CPU/RAM/add-in cards are OK (like PSUs, such circuitry is usually designed to sacrifice itself before letting a short, overcurrent, etc. affect devices downstream.

Unfortunately, yes, you need a new motherboard. (or if under warranty, get this one repaired -- it's a manufacturing defect -- I've had USB shorts happen numerous times when doing embedded device development and while the port may shut down, on a well-designed motherboard a cold reboot will usually bring it back up)

Comments

[David Schwartz]

Umm, are you saying you had the PSU's mobo connector plugged into a tester while the 2x2 was plugged into the mobo?! Also, can you describe the problem in more detail? What happens when you press the power button? Do the fans spin?

[Mokubai]

If the tester says your psu is fine then it may well be that some of the components on your motherboard are dead. Try removing components such as graphics card and hard drives, leaving just CPU and memory and see if it boots or at least powers up.

[psusi]

@Darius, NO! Applying power while the motherboard has numerous points shorted out via foil is a surefire way to blow stuff up!

[Darius]

@psusi Maybe my choice of words was bad, I meant the plasticky pouch the motherboards usually come in. Other then that my claim still stands.

[psusi]

@Darius, no, it doesn't. Again, shorting out points on the bottom of the board and applying power is BAD.

[Mario Garcia]

Yes, i would plug in the 24 pin to the tester (fans and drives would go on) and as soon as I plugged in the 2x2 all would turn off. When I press the power button nothing happes (no fans, drives, nothing) I have pulled the mobo out, placed on a box and plugged in the psu and nothing.

[psusi]

@MarioGarcia, plugging in power to a board that is already partially powered is also a good way to blow it up.

[Mario Garcia]

I have tried two PSUs, do you think i need a new mobo?

[Logman]

You probably do need a new mobo, though I have seen a psu tester plugged in like that and the mobo was fine -> yes I did it, when I got my first tester =)

[David Schwartz]

@MarioGarcia: Yeah, so long as he doesn't tell them what he did. Partially powering a motherboard is not good for its health.

[ish]

@DavidSchwartz: "One day i plugged in my printer on the usb and shorted the pc out" is a manufacturing defect. He can't be blamed for testing things out after his motherboard stopped booting up.

[ish]

And then it just stopped working one fine day...before he tried to troubleshoot it. In any case, all partially powering up a properly-designed motherboard should do is not let it turn on, not blow it up.

[psusi]

@izx, it's the plugging in of the second connector while the motherboard is already on that is the problem.