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  Computer powers on for 2 seconds then dies. 
 
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Chad Smith Jul 12, 2006, 06:12am EDT Reply - Quote - Report Abuse
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I've searched quite a few forums on power supply issues, hoping that someone would somehow have had the same problem that I've had for the past few hours.

My PC is around a year old. It was custom built, including the 560W Thermaltake power supply. Even though I'm running SLI (dual graphics cards), 3 hard drives, 2 CD drives and a pretty big cooling system, I'd still think that 560W can handle all of that pretty well. So I'm playing a game, and suddenly everything powers off. I try to restart, but nothing. I swap out the power cord, and this is where it gets interesting. I power on, and it runs for two seconds then shuts down. I try to power on again... and nothing. I swap out the cord yet again (I've got 10 just lying around), and again, power for 2 seconds then dead. Apparently it wouldn't power on with the same cord twice, but WOULD power on if I used a new one each time. After leaving it alone for 30 minutes, those old cords worked again, but only once, yet again.

Seems like a pretty open-and-shut case for a new power supply, but it's only around a year old and is supposed to be a pretty darn good brand. I don't leave this computer on all the time, and I have another computer that's 2-3 years old that's still powering just fine. Nothing just "came unplugged" inside the case, and I'd like to make certain before I get a new (more expensive) power supply. The whole thing with it not working with the same power cord twice in a row makes it almost certainly a power-supply issue, as anything beyond the supply itself would've at least had nothing to do with the cord-to-computer connection (or so I'd assume). Any help is appreciated.


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Chris McNally Jul 12, 2006, 12:05pm EDT Reply - Quote - Report Abuse
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>> Re: Computer powers on for 2 seconds then dies.
I think your power supply is overheating. Swapping out the power cord gives it a chance to cool down slightly, but only enough to allow for a brief period of operation. Check the fan is turning, but basically, it's time for a new PSU.

Regards,

Chris McNally

Moderator - Hardware Analysis
E-mail: chris@hardwareanalysis.com
john albrich Jul 12, 2006, 12:24pm EDT Reply - Quote - Report Abuse
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Edited: Jul 12, 2006, 12:31pm EDT

 
>> Re: Computer powers on for 2 seconds then dies.
Swapping out the cord also reset the PSU control system. Modern PSUs usually still have power and produce some internal power output even when the computer power switch is pushed to the "off" state. This is for the control subsystem which lets the PSU respond to things like the front "power" button. All taht button is really doing is telling the control subsystem to "wake-up" the rest of the PSU and produce high power output.

Detaching the AC power cord resets the subsystem. You should get the same effect even using the same cord over and over again.

The 2 second delay is telling us that the PSU's internal diagnostics failed, or there is an external condition forcing the PSU back into shutdown mode. It could also be as simple as a fan that isn't running as fast as it should.

Swapping out the cables also may be giving an internal solid-state "fuse" just the time needed to phase-change and reset...thereby allowing the PSU to power-up again, then trip the fuse again, etc.

Try disconnecting most of your devices, and see if the PSU will power up ok.

Try a PSU tester (US$8 to $15) from various vendors such as tigerdirect.com. They are usually designed to provide a minimum load to the PSU and then check the voltage outputs.

And lastly, even a 580W PSU may be insufficiently designed depending on how your computer distributes the power loads on the power rails. For example, I have a 430W PSU that actually provides LESS +5/+3.3V power capacity than a 300W PSU that I have. It can only provide 150Watts of +5/+3.3V power, whereas teh 300W PSU can provide 180Watts on those two rails. Other PSUs can supply as little as 120Watts to the +5/3.3V rails. So, if I've loaded my PC up with a lot of +5/+3.3V heavy devices, even the higher output PSU may be unable to meet the power demands. That's why selecting a PSU ONLY on the total wattage capacity can cause problems. You really need to know what your computer requires from each power rail, and whether the PSU can deliver that power as needed from each output plug.


edited to correct typo

Chad Smith Jul 12, 2006, 02:30pm EDT Reply - Quote - Report Abuse
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>> Re: Computer powers on for 2 seconds then dies.
I've removed all cards and devices, still no go. All fans seem to be working fine, except for the chip fan. I've never really looked at it so I'm not sure if it's supposed to turn this slowly or not, but for those brief 2 seconds that the computer turns on, the chip fan turns extremely slow (hardly budging at all rather), and doesn't pick up speed like the other fans. Is it supposed to do this, or is supposed to always be turning rapidly like the other fans?

john albrich Jul 13, 2006, 12:17am EDT Reply - Quote - Report Abuse
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Edited: Jul 13, 2006, 12:20am EDT

 
>> Re: Computer powers on for 2 seconds then dies.
The fan should be spinning quite a bit faster than that.

The following can depend on the actual mobo design, but you might look into...

Can you temporarily plug the fan power cable into a different fan, or plug a different fan into the fan power jack? (one with speed sensor and make sure it doesn't draw too much power).

If it then powers up ok, then you found a bad fan or connector or something in-between. It's also possible that you have a bad speed sensor/wiring telling the system the wrong info, and that could have an unpredictable effect on operations depending on the precise design.

If it did power up ok, do not keep it powered on for more than a very short amount of time without a properly mounted cooling fan. Just long enough to verify that it stays reliably powered-up for more than the "2 seconds" you mentioned.


If it still did not power up ok, then the problem lies elsewhere. Here are a few more ideas:

Fan speed controller circuitry
Output voltage from the PSU to the fan or fan controller (if you're using a separate fan power cable)
Bad PSU
Under-rated fan wiring or damaged wiring/connectors. Some of these CPU fans take a LOT of power.... especially after-market fans...sometimes much more than the standard mobo design can handle.

If you're using an after-market fan, it may have an integrated controller that has failed. Or, it may have caused your external control unit to fail if that's what you're using. Try another fan control port if possible.

Chad Smith Jul 13, 2006, 03:00am EDT Reply - Quote - Report Abuse
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>> Re: Computer powers on for 2 seconds then dies.
The motherboard is the ASUS A8N-SLI Deluxe. Unfortunately the small cord for the CPU fan doesn't reach all the way down to the chip fan power plug and vice versa, so there's no way for me to test them opposite each other. I've read that the chip fans have had a problem on this motherboard in terms of them being too loud, and that ASUS has replaced them for free at no cost. So now that a new chip fan is in the mail, I can only hope that does the trick. The CPU and the other 9 billion cooling fans inside the case work fine. If you define an "aftermarket" fan as one not made by the motherboard manufacturer, then I guess my CPU fan is aftermarket, though I'm still unsure why the the computer would decide that anything inside the case is suddenly "too much" after having run flawlessly for so long now. So whatever "broke", I only hope I can eventually narrow it down. Thanks for the tips.

john albrich Jul 13, 2006, 06:30am EDT Reply - Quote - Report Abuse
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Edited: Jul 13, 2006, 06:41am EDT

 
>> Re: Computer powers on for 2 seconds then dies.
"...though I'm still unsure why the the computer would decide that anything inside the case is suddenly "too much" after having run flawlessly for so long now"

If it's been operating near or above the maximum power capability of the fan controller, wiring, or connectors, then the overheating of components over time could eventually cause a failure.

Some of the aftermarket fans (like Zalman) consume a lot of power. I think many Zalmans consume in the region of 5Watts or so. There are Zalmans that consume 9.6Watts and higher. I don't have the figures handy, but I recall researching this some months ago and there are even 12V fans out there that consume over 15Watts (Vantec, Tornado). Motherboards cannot handle those fan power requirements.

The motherboard fan connectors, wires, circuit board traces, control electronics, etc. were not designed to handle those high wattage requirements. I recall reading one recommendation to never plug into a motherboard any fan that requires more than 4Watts of power. (that's means keep it to less than 0.33 Amps) Any more than that, and you risk damaging your motherboard. I'd personally add a safety margin to that and say don't use any fan more than 0.25 Amps connected directly to the mobo, but read the mobo specs regardless.

Use a separate properly rated fan controller as needed. (e.g.the "VANTEC NXP-205-BK Black Fan Controller Panel" provides up to 18Watts fan control per channel...not promoting Vantec, it was just a handy reference)

Chad Smith Jul 15, 2006, 04:05pm EDT Reply - Quote - Report Abuse
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Edited: Jul 15, 2006, 04:10pm EDT

 
>> Re: Computer powers on for 2 seconds then dies.
Well, long story short, it was the power supply. Good thing I guess, I'd rather spend $160 on a new power supply than the same amount just to have someone look at it and then tell me how much more I'll need to spend to get it fixed. 650W should be enough, plus a lifetime warranty isn't too bad either. My only question is, this new PSU has "dual rails", I guess that's why there's a second 4x4 12v pin. Only thing, my motherboard only has one input. Does the motherboard need two inputs, do you just couple them (provided that wouldn't blow anything up...), or what? I'm a "dual rail" n00b.

Chris McNally Jul 15, 2006, 04:46pm EDT Reply - Quote - Report Abuse
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>> Re: Computer powers on for 2 seconds then dies.
If your mobo only has one input, then one is all you need.

Regards,

Chris McNally

Moderator - Hardware Analysis
E-mail: chris@hardwareanalysis.com

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