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Fan shorted and now motherboard will not turn on

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September 19, 2009 9:33:28 PM

Hey hardware wizards,

Apologies for the repost, but my original post was under a vague title and wasn't particularly descriptive...

I've been assembling a new build with the following spec:

intel i7 920
6gb OCZ gold RAM
ASUS P6T Deluxe v2
ATI Radeon HD 4790 1GB
WD Caviar Black 1TB
Zalman CNPS10X Extreme
OCZ ModXtreme 600w PSU

After having some initial problems with the build, I bread-boarded it, and removed everything except the CPU and heatsink. Everything lit up and started working, so I added RAM and the graphics card, and it POSTed successfully.

Then, I tried attaching the case fans, and on power up, something appeared to short (there was a flash of light and everything cut out). Since then, I've been unable to turn the thing back on, and the power and reset buttons on the motherboard itself are flashing (before they were on solidly).

Can you suggest what the problem might be? I suspect possibly a problem with the PSU, but I've used the paperclip test suggested in the sticky and the fan starts spinning. Any ideas?

Thanks in advance.
September 19, 2009 9:51:20 PM

How did you have your fans wired when the short was caused? Was it just connected to the motherboard and which fan was it?
September 19, 2009 10:01:26 PM

The fan was wired to the PSU. Not sure what the name of the connection type is (i think they have 4 pins, and you can connect them in serial)
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September 19, 2009 10:18:32 PM

twbaker said:
The fan was wired to the PSU. Not sure what the name of the connection type is (i think they have 4 pins, and you can connect them in serial)


I believe that is molex. Also, give better details about your situation. Pictures would be nice too. Does the motherboard light up (there's a green light i believe) when you connect the PSU (24pin)?
September 19, 2009 10:29:06 PM

I can't get any pictures right now, but will post some in the morning (i'm in the UK)... Not sure how much help they will be though...

At the moment, all I have installed is the CPU and the heat sink. The 8 pin cpu connector is plugged in and so is the 24 pin motherboard connector. The heat sink fan is connected to the CPU fan connector. I've disconnected the case fans and all the other components.

There are no other lights on on the motherboard. The power switch flashes orange and reset switch flashes green. Also, they continue to flash after I've switched the PSU off which I guess means that the motherboard battery is what's powering the lights and making them flash.
September 19, 2009 10:37:24 PM


Quote : "Then, I tried attaching the case fans, and on power up, something appeared to short (there was a flash of light and everything cut out). Since then, I've been unable to turn the thing back on, and the power and reset buttons on the motherboard itself are flashing (before they were on solidly). "

So you were saying everything worked BEFORE the attachment of the "case fans". Correct?

Does the mobo light flash now? And for how long?

Quote: "There are no other lights on on the motherboard. The power switch flashes orange and reset switch flashes green."

There is a light on the mobo. The power switch can't flash..neither can the reset switch..
September 19, 2009 10:43:07 PM

As far as I know everything was working before attaching the case fans. I hadn't attached a monitor before this happened, but prior to the case fans, All the lights on the mobo/hsf etc came on and the psu fan, gpu fan and heat sink fan were both spinning. During post I had a single beep, followed by 4 beeps (according to the mobo manual that just indicates that there's no monitor attached), and then everything turned off automatically.

The motherboard power and reset lights flash when the PSU is switched on. When the PSU is switched off, the lights continue to flash for a further 10-20 seconds or so.
September 19, 2009 10:46:58 PM

Nothing turns on now? Not even fans spinning? Any beeps? Lights?
September 19, 2009 10:49:47 PM

Nothing turns on. No fans spinning, no beeps, only the lights in the power switch and reset switch are on.
September 19, 2009 11:21:25 PM

Have you tried removing ram, video card and booting it? what solutions have you tried?

the least likely to occur, try another power outlet or test the power outlet you are connected to with a charger for a phone?
September 20, 2009 2:06:09 AM

I would unplug the PS from the outlet until the lights go off on the MB and then plug it back in and try again.
September 20, 2009 7:41:39 AM

I've tried with no video card or RAM and that still happens. I've tried a different power outlet, still the same result. And I've tried waiting until the lights go off, and plugging it back in to try again, always the same result.
September 20, 2009 2:57:47 PM

If you are really lucky, something in the PSU died.

The following is cut & pasted from a previous thread that I replied to:

Try to verify (as well as you can) that the PSU works. If you have a multimeter, you can do a rough checkout of a PSU using the "paper clip trick". You plug the bare PSU into the wall. Insert a paper clip into the green wire pin and one of the black wire pins beside it. That's how the case power switch works. It applies a ground to the green wire. Turn on the PSU and the fan should spin up. If it doesn't, the PSU is dead.

If you have a multimeter, you can check all the outputs. Yellow wires should be 12 volts, red 5 volts, orange 3.3 volts, blue wire -12 volts, purple wire is the 5 volt standby.

The gray wire is really important. It sends a control signal called something like "PowerOK" from the PSU to the motherboard. It should go from 0 volts to about 5 volts within a half second of pressing the case power switch. If you do not have this signal, your computer will not boot. The tolerances should be +/- 5%. If not, the PSU is bad.

Unfortunately (yes, there's a "gotcha"), passing all the above does not mean that the PSU is good. It's not being tested under any kind of load. But if the fan doesn't turn on, the PSU is dead.
--------End cut&paste-------

The voltages can be checked from the back of the main power plug also.

If it turns out to be the PSU, I recommend Corsair, Antec, PC P&C, or Seasonic.
September 20, 2009 6:21:50 PM

And if I'm unlucky?

I've done the paper clip test and the fan spins... will see if I can get my hands on a multimeter...
!