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Computer turns on for a split second then shuts off

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January 7, 2011 9:40:31 PM

I have looked at a bunch of forums trying to figure out what the issue is here but it seems that no one is has quite the exact same problem..

What's happening is when I try to start the computer it turns on and shuts off immediately. Case fans, CPU fan, GCard fan, case LEDs and PSU fan all turn on for that half second. If I press the power button again, nothing happens.. The only way I can get it to attempt to startup again is if I flip the power supply off and on again, but it still does the same thing. Oddly, if I try it over and over again enough times, it will eventually boot and run. I can restart the computer from windows and it restarts fine, but if I shut it on and off it still has that same issue. It has come down to flipping my power supply on/off a hundred times trying to get it to start with it eventually working.

This happened randomly after owning my computer for about 5 months, nothing changed whatsoever, I just tried turning it on one day and it happened. I'm not sure if it's just me but it seems to be getting worse and worse. I have tried different outlets, cleaning out everything, and unplugging all other cords except the power cord. It's not the power button itself either..

A strange thing that happens is if I turn my PSU off, unplug it, turn it on, and push the power button it will do the split-second turn on.. If i turn the PSU off and on again after that, when I push the power button it will run everything for about three times longer than usual.. (about a second)

AMD Phenom 965 @ 3.4 ghz
2 x 2gb Gkill
XFX Radeon 5770
OCZ 700w PSU
Asrock 790gx mobo
Sunbeam Transformer Case
Anonymous
a b B Homebuilt system
January 7, 2011 9:48:15 PM

Just putting it out there, did you try turning it on with the PSU switched the other way?
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January 7, 2011 9:53:23 PM

Quote:
Just putting it out there, did you try turning it on with the PSU switched the other way?


Yes.
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a b B Homebuilt system
January 7, 2011 10:37:46 PM

Do you ever push the power button, let it turn on and off, and then wait for about 10 seconds? If you keep turning off the PSU (i.e. draining all of the capacitors), it has to recharge them, so the computer will shut off momentarily to charge, and then continue booting up.
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January 7, 2011 11:12:34 PM

boiler1990 said:
Do you ever push the power button, let it turn on and off, and then wait for about 10 seconds? If you keep turning off the PSU (i.e. draining all of the capacitors), it has to recharge them, so the computer will shut off momentarily to charge, and then continue booting up.


Just tried it and nothing
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a c 122 B Homebuilt system
January 7, 2011 11:38:35 PM

When you have problems, you need to post complete system specs.

boiler1990 said:
Do you ever push the power button, let it turn on and off, and then wait for about 10 seconds? If you keep turning off the PSU (i.e. draining all of the capacitors), it has to recharge them, so the computer will shut off momentarily to charge, and then continue booting up.

Not true. When you turn a PSU on, only the small 5 volt standby power supply is working. The main power section is off with discharged capacitors. When you turn on the PSU with the case switch, the PSU starts to cycle up. When the main voltages reach operating levels, the PSU sends a control signal to the CPU telling it that the PSU is fully on and it is OK to boot.

Work systematically through our standard checklist and troubleshooting thread:
http://www.tomshardware.com/forum/261145-31-read-postin...
I mean work through, not just read over it. We spent a lot of time on this. It should find most of the problems.

If not, continue.

I have tested the following beep patterns on Gigabyte, eVGA, and ECS motherboards. Other BIOS' may be different, but they all use a single short beep for a successful POST.

Breadboard - that will help isolate any kind of case problem you might have.
http://www.tomshardware.com/forum/262730-31-breadboardi...

Breadboard with just motherboard, CPU & HSF, case speaker, and PSU.

Make sure you plug the CPU power cable in. The system will not boot without it.

I always breadboard a new build. It takes only a few minutes, and you know you are putting good parts in the case once you are finished.

You can turn on the PC by momentarily shorting the two pins that the case power switch goes to. You should hear a series of long, single beeps indicating memory problems. Silence indicates a problem with (in most likely order) the PSU, motherboard, or CPU. Remember, at this time, you do not have a graphics card installed so the load on your PSU will be reduced.

If no beeps:
Running fans and drives and motherboard LED's do not necessarily indicate a good PSU. In the absence of a single short beep, they also do not indicate that the system is booting.

At this point, you can sort of check the PSU. Try to borrow a known good PSU of around 550 - 600 watts. That will power just about any system with a single GPU. If you cannot do that, use a DMM to measure the voltages. Measure between the colored wires and either chassis ground or the 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. 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...

A way that might be easier is to use the main power plug. Working from the back of the plug where the wires come out, use a bare paperclip to short between the green wire and one of the neighboring black wires. That will do the same thing with an installed PSU. It is also an easy way to bypass a questionable case power switch.

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.

If the system beeps:
If it looks like the PSU is good, install a memory stick. Boot. Beep pattern should change to one long and several short beeps indicating a missing graphics card.

Silence, long single beeps, or series of short beeps indicate a problem with the memory. If you get short beeps verify that the memory is in the appropriate motherboard slots.

Insert the video card and connect any necessary PCIe power connectors. Boot. At this point, the system should POST successfully (a single short beep). Notice that you do not need keyboard, mouse, monitor, or drives to successfully POST.
At this point, if the system doesn't work, it's either the video card or an inadequate PSU. Or rarely - the motherboard's PCIe interface.

Now start connecting the rest of the devices starting with the monitor, then keyboard and mouse, then the rest of the devices, testing after each step. It's possible that you can pass the POST with a defective video card. The POST routines can only check the video interface. It cannot check the internal parts of the video card.
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a b B Homebuilt system
January 7, 2011 11:52:43 PM

Even OCZ power supplies occasionally fail......
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January 8, 2011 1:48:58 AM

Thank you so much! I'll try everything you said until I get some indication on what's going on.
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January 9, 2011 10:26:13 PM

I did the PSU test with the paperclip and it turned out to be the culprit. The weird thing was that after trying about 8 times and watching it fail, it decided to start working. I tried it over and over again trying to get it to fail and it wouldn't.. I have it in my system right now and it's working fine. Beats me..
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a b B Homebuilt system
January 9, 2011 10:41:32 PM

It must be the PSU god
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January 20, 2011 11:01:54 AM

Best answer selected by Zack199.
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November 26, 2011 12:38:58 PM

Mine did exactly the same thing and it was the video card
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December 27, 2011 10:18:23 AM

I fought w/this for a week. Finally figured out the problem. Think about it: turn it on and shuts right down, the computer is protecting itself from a short circuit. Took the screws out of mobo and cut a piece of thin cardboard same size as mobo. slid it under mobo between case and mobo.viola it worked.
took out cardboard and retightened screws, same problem occurred. loosened srews half turn and worked again. problem is the mobo is shorting out on the case because it was tightened to tight to the case. Back off your srews in the mobo to the case a half turn and you should be good. worst case keep the thin piece of cardboard under the mobo and srew mobo back down therefore iliminating short. have fun!!!no stress
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February 15, 2012 4:22:00 AM

Hi Zack199
I had the same problem with my computer. I got some advice from an IT expert....well my situation was exactly like yours i.e turn on comp, all lights and fans turn on and turns off 1 second later.

Solution:
1. Disconnect all power cables and monitor cables
2. Pull out all the ram from each of their ram slots (n.b make sure you put it back in the same order aswell)
3. There is a button type battery located somewhere on the motherboard, have a look for it and simply pull or pop it out.
4. Flip the battery upside down and put it back into the motherboard
5. Put all the ram back into their slots in the same order you took them out
6. Push the power button and keep pushing the power button continuously until you hear the hdd and other stuff kick it (push it maybe 5-10 or so times)
7. The cpu should hold out and you should hear the beep and the computer should load something where it prompts you to continue or setup (the usual stuff)
8. Press the button that says continue. In my case i have an AMD and it said "press F1 to continue"

Let me know how it goes :)  goodluck
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February 15, 2012 1:59:35 PM

This topic has been closed by Mousemonkey
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