Need help troubleshooting a 'dead' PC

[thatenglishdude]

Hello Tom heads!

So I've recently built a new system:

Intel i5 750
Geforce GTS 250 OC
4GB DDR3 Ram
HT Striker 7.1 sound card
Windows 7 64 Bit
Corsair 750w PSU

Very sweet system indeed and has been performing fine until today. I recently check the temperatures and to be honest - they were fine. Low - mid 40's.

I have to rush out, come back a few hours later to find my PC is off and will not power on!

I've tried unplugging the cord, trying a different cord in different outlet. Used canned air to remove dust, left it unplugged and plugged back in 30 minutes later - all with no luck. I don't get a single light on the motherboard come on. I don't know what caused this, and was just requesting assistance on what things I could try.
As of right now - everything is unplugged other than the monitor - which turns on just fine (just on standby waiting for PC)

Is it possible for PSUs to simply overheat and die this easily? I do have a rather popular unit and was recommended by many. I know not all are going to be perfect but the system has been just fine until today.

Any ideas would be much appreciated.

-ThatEnglishDude

 

[JohnnyLucky]

Here is a link to the "System won't boot" and "no video output" checklist:

http://www.tomshardware.com/forum/261145-31-perform-steps-posting-boot-video-problems

Please do the entire checklist and be sure to click on the links to additional help.

Good Luck!

 

[thatenglishdude]

I followed every step on that page to the best of my abilities and still - no luck.

What would make the power supply just fail like that?

Like I said - it was working fine, I went out for a few hours, come back and it's just not working. I just fail to see how this could happen to begin with. Anything else you can suggest?

 

[popatim]

If you have a voltage meter and a spare old working harddrive you can try the following.
Unplug all the power supply connectors inside the case and plug in 1 molex connector to an old working harddrive. Just the molex, do not plug in the hdd data cable (ide or sata).
Now you can force the power supply to turn on by jumpering the lone green wire to a black wire right next to it on the large power supply connector that goes to the motherboard. If this does not turnon the power supply then it indeed is bad.

If it turns on then you can test voltages on this big motherboard connector.
The following colors are for standard power supplies. Some system manufacturers use non-standard supplies and you need to look up those up but they should all use the same atx pinout.

Black is ground and should be 0v
Red is 5v DC
purple is 5v dc and always on if power supply is plugged in.
Yellow is 12v dc
Orange is 3.3v
white is -5v dc
blue is -12v dc

You may not have the negative voltage wires, these are legacy.

 

[pjmelect]

It sounds like the power supply has failed, check that you have good air flow though the computer and that the back of the power supply has at least two inches clearance from the wall.

 

[popatim]

As for what caused it, did it storm in your area? If it did a power spike may have taken it out. I've got a very expensive 100Kw ups behind me being worked on, right now in fact, for that very reason. LoL

 

[thatenglishdude]

Well the odd thing is - my fiancees pc is about 6 ft away. Albeit on a different outlet and hers is fine. Both monitor and pc. My monitor turns on just not the pc. And I don't think we've had any storms either. Its been really hot infact.

I don't have the box for it anymore but I do have the receipt from best buy...

 

[jsc]

The motherboard LED is powered by the standby power supply inside the PSU. If it is off, it's either something simple like wall outlet, switches, or cabling; or either the PSU or the motherboard is dead.

The best way to test a PSU is to replace the PSU with a known good one of similar power capacity. Brand new, out of the box, untested does not count as a known good PSU.

Next best thing is to get (or borrow) a digital multimeter and check the PSU. Measure from the colored wires to ground (black wires).

Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.

You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires.

http://www.youtube.com/watch?v=5FWXgQSokF4&feature=youtube_gdata

This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU. You can carefully probe the pins from the back of the main power connector.