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Computer won't power on. Help!

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June 22, 2010 10:51:59 PM

I built my own system two or so years ago and just started having problems not too long ago. I was playing a game one day, and my computer turned off without warning. This kept happening over a period of a week until the computer stopped powering on. I smelt a burning smell and figured it was just my power supply, so I went and bought a new power supply, same specs: 500 watt, and to no avail. So I went out and purchased a new motherboard and voila, it worked.

A few months down the road--yesterday--my computer started to lag a bit when playing a game and then shut down without warning. I manually tested the power supply with the paperclip test, it works. I tried disconnecting everything and attempted to power the pc. Now, after connecting the power supply and all of the little odds and ends it connects to, I get a quick, quarter of a second jolt of power and the case lights come to life, but only for a quarter of a second before it powers off again, at which point I have to turn the power supply's |/O switch to off, wait a ten seconds, and try again only to arrive at the same result. ch ma

I figured the power switch may be the problem and attempted to jump the power by removing the switch and touching the two pins of the power switch mother board connectors together only to arrive at the same result of a quarter of a second of life.

So, what could be the problem? Any tips and/or ideas to help me arrive at identifying the problem?

I would list all of my computer stats here, but I can't turn it on. A friend helped me build it and I therefore don't know all of the parts:
It's an am2 processor of some sort, dual core
1024mb egeforce 8800GT
2 gb of ddr2 ram
500 W power supply
dvd drive

More about : computer power

June 22, 2010 11:38:36 PM

Which power supply are you using? It could also be overheating somewhere...
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June 22, 2010 11:45:06 PM

most electronics and or products in general these days have a big old piece of writing on dem called brand name.

Let us know what the brand and models are just by looking at most any part.

I recently had a problem like yours that could involve virtually any hardware piece on my pc. This is one neato article i googled.

http://pcsupport.about.com/od/findbysymptom/ht/pconthen...
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Related resources
a b B Homebuilt system
a b ) Power supply
June 23, 2010 12:09:52 AM

Well, it could be either the PSU or the mobo again. If it's the mobo, surely it is still under warranty.

But check this first. Open the case and watch the CPU cooler fan when you power on. Does it start up OK? If not, or even if it does, try this. Disconnect it from the mobo pinout that powers it, then plug it back in. Repeat a couple of times. Leave it properly connected and try starting again.

I'm hoping for a small miracle here. Most mobos have a system that checks the CPU cooling fan speed. But some go further. If they see no speed they will shut down the whole system right away to protect the CPU from overheating, rather than wait for the CPU temperature sensor to detect real overheating. So if that fan is not getting power, OR if the fan's speed signal line is not making good contact with the mobo pinout, just MAYBE that is what's happening.

I gotta admit, though, this does not really sound like your problem. When it's this fan speed thing, the power usually stays on for several seconds - say, 4 to 10 anyway - before shutting down. The VERY brief power pulse you describe is more like a failed PSU or a short in the mobo.
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June 23, 2010 12:24:55 AM

My PSU is an Apevia Switching Power Supply Model No: Win-500XSPX
Dc Ouput: 500 W

Thank you all for the quick and helpful replies! I will try what you suggested, Paperdoc, and relay the results. I am also taking a look at the article suggested.
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June 23, 2010 1:04:12 AM

Update: It seems that the fan isn't the issue as I tried what Paperdoc said :(  . If it is, in fact, the motherboard, and if it is under warranty, what would be the next step? The place I bought it from went out of business.
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June 23, 2010 1:44:16 AM

arg if company has failed then tech support has also failed obviously.

u will have to purchase a mobo of similar performance if ur sure thats the piece.

I am also really interested in what this could be. Keep the replies coming.

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June 23, 2010 5:52:31 AM

I will for sure. I ordered a new case and power supply on new egg, which may or may not solve the problem. Of course if it is a deeper rooted problem, I don't know hopefully i can figure this out.
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a b B Homebuilt system
a b ) Power supply
June 24, 2010 6:01:42 PM

"The place I bought it from went out of business." I presume you mean the retailer. What about the mobo manufacturer? Are they not the source of service and replacement for a bad mobo?
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a c 122 B Homebuilt system
a c 144 ) Power supply
June 25, 2010 7:29:05 AM

feldwebel said:
I manually tested the power supply with the paperclip test, it works.

By"works", I assume that you mean that the PSU fan spins up.

Unfortunately, that just doesn't mean much. All that tells you is that the PSU can provide some small (very small :) ) amount of 12 volt power. It doesn't test the 3.3 or 5 volt outputs and it doesn't test the "PowerOK" control signal. And it puts no significant load on the PSU.

The best way to test the 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. 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. Tolerances are +/- 5% except for the
-12 volts which is +/- 10%.

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=yout...

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.

Try breadboarding the system:
http://www.tomshardware.com/forum/262730-31-breadboardi...

I have a paragraph there explaining how to build and test the PC in stages.


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June 25, 2010 7:38:04 AM

Update: Well, my new case an PSU arrived today, and neither solved anything as I 50% suspected. Here's an interesting but of info, however: after trying to turn the power on for the second time today with the new power supply, I heard a crack as I was almost hit by a spark. After this, I smelt the familiar burning smell I had smelled when my previous mobo blew. Upon further inspection of the mobo, I noticed that one of the little black squares, that serve some important purpose, was chipped, which I suspect happened because of the spark. It has occurred to me that I now need a new motherboard.

What really bothers me, though, is the fact that this has happened before--possible under different circumstances--and now I wonder what caused two of my mobos to be rendered kaput? I don't know if the reason for the mobo blowing this time has any link and/or relation to my previous mobo blowing. Maybe there is a faulty piece of hardware that has caused both mobos to blow? Perhaps this is a coincidence and I happened upon a faulty board? I have more questions than answers, which is frustrating.

By the way, my current motherboard, the one that I believe has just blown, is a MSi K9N6PGM2-V2 Model no. Ms-7309. My previous mother board was a similar, but older, board. My processor is an AMD Athlon 64 X2

Any ideas?
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June 26, 2010 3:00:39 AM

Any ideas, people? Sorry for bumping.
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