Mainboard or PSU dead?

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Arancaytar
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Mainboard or PSU dead?

Postby Arancaytar » Mon Feb 02, 2015 9:43 am UTC

I seem to have bricked my desktop simply by opening the case to look at something. Since then, not only will it not power up, but even the power LED on the mainboard remains dark when the PSU is switched on.

Since I didn't intentionally touch anything, my main suspects were nudging and disconnecting a cable (checked those), or brushing something and frying it with a static discharge. But I'm stumped by this effect - in the past, even the most severe mainboard fault I've had just caused it not to reach POST, while the LED and the CPU fan worked normally.

What checklist should I follow here? I'll probably end up replacing parts until it works again, but I don't know where to start, or what to test for faults (and how).
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Re: Mainboard or PSU dead?

Postby bachaddict » Mon Feb 02, 2015 9:58 am UTC

I would use a multimeter to check that the PSU is delivering the voltages it should. Very unlikely that it isn't, but it's one thing to eliminate.

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Re: Mainboard or PSU dead?

Postby Xenomortis » Mon Feb 02, 2015 10:36 am UTC

Possibly there's a short-circuit? Can't remember the exact symptoms of the last one I saw.
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Re: Mainboard or PSU dead?

Postby Arancaytar » Mon Feb 02, 2015 3:41 pm UTC

Thanks for the tip! I guess I'll find a voltmeter.

Since the board and CPU are about five years old now, I expected to have to replace the system sooner or later; this is just a bit sooner than I'd planned. If it does turn out to be dead, I hope I can salvage most of the other hardware (GPU and memory) at least.

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English is fine; also wow that is seven years out of date. :D
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Re: Mainboard or PSU dead?

Postby Arancaytar » Tue Feb 03, 2015 4:29 pm UTC

Update: Haven't acquired a voltmeter yet, but apparently I might not need to:

Unplug the power supply from any of the components inside the computer (or just remove it from the computer completely). Find the big 24-ish pin connector that connects to the motherboard. Connect the GREEN wire with the adjacent BLACK wire. The power supply's fan should start up.Oct 17, 2013


Guess I'll try that next.
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Re: Mainboard or PSU dead?

Postby AndyG314 » Mon Feb 16, 2015 9:13 pm UTC

If a desktop suddenly stopped working after popping the top, my first advice would be to re seat every connector, especially those which you might have disturbed. A loose connector will sometimes cause this sort of problem especially if it's after you were just messing around in there. Check this carefully before moving on, I have spent hours debugging problems just to find it was one loose cable that I missed.

The next thing I would look at is the psu. First make sure that the fan comes on when it should. This doesn't mean that the PSU is good, it's just the first step. Secondly you should meter out each of the rails to make sure that it is giving the right voltage. Even this can't ensure that the PSU is good, as it could be drooping the voltage when under load (the meter is essentially no load).

Assuming that it meters OK and the system still won't boot, and I didn't have a spare psu to try, I would unplug everything from the mother board except the cpu. You should be able to get to the bios in this state if it doesn't then you know the problem is the psu, motherboard or chip. The pus is probably cheapest to replace, so start with that, if it still doesn't work, then I would decide that it's time for a new computer. As finding a new mobo or chip for a 5 year old computer is probably not worth it.
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