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PC won't power on

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June 5, 2009 2:18:56 AM

I have a problem with a computer that has important information stored on the hard drive, but not backed up on any other hard drive so I would really like to get it working. I cannot get it to boot up. When I hit the power switch, the motherboard lights flash on and the fans start to spin for about a split second like it's trying to boot, then they go off and everything goes silent. There are no POST beeps, the keyboard and mouse dont power on. It's like the system is dead. All this happened after I replaced my old power supply today which had been showing signs of dying the last couple weeks(I had to unplug the power cord from the wall for a minute before booting up the last couple weeks), and now my computer no longer powers on with either the new or old power supply. At first I thought the problem was a broken power switch, but I tried manually powering on the computer by shorting the positive and negative power switch pins on the motherboard and the result is the same as pressing the power switch button : nothing happens. I then thought maybe the new power supply, a Rosewill RD500, was incompatible with the motherboard, an Abit KN9 since the motherboard was designed years before the new power supply. To test that out, I put the old power supply back and tried to boot up, but still nothing happened.

I am trying to figure out what I can do about this since I really need to get to the information stored on the hard drive. Is the problem with the power supply or motherboard? It would seem since the computer totally lacks power that it's a power supply problem, but I have tried 2 power supplies today and neither works. Could a faulty power supply have destroyed the motherboard? To complicate matters, my Windows version is XP Media Center OEM. From I've read about it, OEM Windows won't let me use a computer after I get a new motherboard model. The thing is, Abit KN9 SLI motherboards are no longer for sale, so I cannot fix my computer by replacing my motherboard(if it's dead) with another Abit KN9 motherboard. If anyone has any ideas, I would appreciate it.

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June 5, 2009 2:41:01 AM

Yes, A bad power supply can cook any of your components not just the MB. If you've tried multiple power supplies then they're not the common denominator. I sometimes forget the CPU power after plugging the mainboard so double check that.

MS will give you a message in windows telling you that you need to contact support. Windows does not stop your machine from posting when it expires.



a b V Motherboard
June 5, 2009 2:05:24 PM

Did you try with just the motherboard, CPU, HSF, and ons stick RAM?
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a b V Motherboard
June 5, 2009 2:06:24 PM

If you can get the fans to spin for a second, it means the PSU wants to power on the motherboard but it runs into some type of a short circuit. When my videcard I had the same same symptons but I tested the PSU on a separate system and it was fine.
June 6, 2009 2:08:39 AM

I just tried a bare bones boot up with PSU, Motherboard, CPU, and RAM and got the same result- the power-on LED flickers and the fans start to turn for half a second before going to sleep again. So it could be either the power supply, the motherboard or the CPU that's disfunctional. Should I just replace all 3, or can I somehow rule out another part or 2 as needing replacement?
June 6, 2009 6:33:46 AM

Hi, I am having pretty much this exact same problem with my new machine. My first go-through, the thing worked fine for about a day or two. Then it suddenly shut down (I assume. It was on and I left the room and some time later I came back and it was shut down and wouldn't come back on.) Now you power it on and the LED lights on the case AND motherboard come on for a second, every fan spins for a split second and then it shuts off completely. I went through an RMA with my motherboard after about a week of troubleshooting. I determined it was the motherboard. Well, I got my replacement mobo today, and it's still busted. Completely. One thing I can say is that this does not appear to be an issue with the power supply. I swapped power supplies with my old computer. Neither the old or new power supply work on the new computer. Both work on the old computer. Right now, I'm typing this on my old computer which is being powered by my new Corsair 650W PSU.
This seems very similar to your situation doesn't it Hilbert? As far as I understand, this is not an issue with the GPU, because if it were, it would still power on, it just wouldn't boot. I tested the RAM with just one stick at a time in different slots, and that's no good either. The possibilities here that I see are that it is the motherboard, and newegg just sent a DOA replacement, it's the CPU, BOTH sticks of RAM died. The other thing I was thinking was that maybe the PSU is bad, and has damaged my parts in the new computer, but why is it still running fine on my old machine? I'm at my wit's end here. I'm leaning towards it being the CPU. The only possibilities with the PSU is that the PSU is incompatible with my Mobo, which I'm not sure how I would know that. The connectors match up perfectly, 24 pin and a 2x4. In my old computer which is running fine the mobo supports 24 pin and a 2x2. I'd think that the new mobo would be more suited to this PSU than the old computer's mobo is. This brings up another minute possibility that just some of the connectors in the one half of the 2x4 cord of the PSU are fried, so it works fine when only half is connected, but not when all 8 are. Seems very unlikely though.

I know I wrote a lot, but I've been through a lot and I thought the full picture might help the original poster out.

Hundred Island, what you say seems likely, that it is a short circuit somewhere in there, but I don't know how to check for that.

Anyways, here are the key parts of my rig:

GIGABYTE GA-EP45-UD3R LGA 775 Intel P45 ATX Intel Motherboard
CORSAIR CMPSU-650TX 650W ATX12V / EPS12V Power Supply
Intel Core 2 Duo E8500 Wolfdale 3.16GHz LGA 775 65W Dual-Core Processor Model BX80570E8500
G.SKILL 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 1066 RAM
SAPPHIRE 100245HDMI Radeon HD 4850 512MB 256-bit GDDR3 PCI Express 2.0 x16


a b V Motherboard
June 7, 2009 6:44:35 AM

You tried breadboarding? You should get beeps with just the CPU and HSF. It could be your RAM got fried. Look at each stick closely under a magnifying glass for bubbling or scorching.
June 7, 2009 10:40:28 AM

had a similar case in a friends machine the other day, we ended up removing the mobo from the case completely and redoing all the wiring outside of the case to test there wasnt any shortcircuits, i think eventually it was a loose connection because it did start working.

you can always remove the hard drive and put it into another machine to get the documents off it.
June 7, 2009 3:21:22 PM

You could have put the power pins in wrong, such as keyed off one pin or missed the +12 connector. Trto verify all connections on the old supply again. Unfortunately, the newer supply could have cooked something. Was there a smell?
During power up, do the keyboard lights quickly come on. You can try powering up with just external drives ( DVD, CD, Fan ( using older fan conn.) If you really are in a fix, get it off to me and I will back up your data.
June 7, 2009 8:02:08 PM

Right now, I already ordered a new power supply, motherboard, and CPU and I'm waiting for those to install them. I figured that my motherboard is dead and needs to be replaced. I recall plugging a floppy drive power connector into the system fan connector when I installed the power supply. Why did I do that? Because I'm inexperienced and thought something was supposed to go there, and the floppy drive connector fit. At this point, I'm hoping that my other parts - RAM, hard drive, video card, and sound card still work and can be used with the new motherboard I ordered. I am also hoping I can call Microsoft and they will let me use my Windows XP OEM key after I change motherboard, since I had to replace a dead motherboard. I had to switch to a completely different model of motherboard because my original motherboard- K9N SLI is out of production and not for sale.
June 13, 2009 1:03:28 AM

Hello again. Trying to solve this issue, I sent my CPU in for replacement. I received the new one today, and the problem seems to be solved. No issues turning it on. I haven't yet set it up on a monitor yet but the second i put the new CPU in and booted up, no issues it stayed on and all the fans, lights and beeps were fine. Hopefully Hibert this means that you will have fixed your problem as well. I suspect the CPU is what died or was fried in both of our machines. Good luck, and let us know if your new hardware works.
June 13, 2009 2:02:36 AM

Yes, thanks to all the respondents. After installing a new motherboard and CPU my system is up and running. I did not have to even call Microsoft to reactivate Windows. Internet activation worked for my once-used OEM XP MCE key. The biggest problem I had was I could not install Service Pack 3 after repairing Windows due to some .net framekwork files being missing or corrupted. And some basic windows functions like defrag wouldn't work. So I ended up backing up my important files and then reformatting and installing windows.
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