Computer powering on then off then on then off ect

Spiz

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This morning my desktop was locked up I had left it on overnight. I used a hard reset and when it started to power back on it powered off again about 3 seconds later. It continued doing this in a loop until I switched off the power supply. I've never ran into this problem before so I am stumped. I've tried several things and removed most of the hardware. video cards, Hard drive, Disk drives and the memory 1 stick at a time. Each time the same problem continues. I've tried clearing the cmos by removing the battery on the motherboard for about 5 min then replacing it to no avail. I've ordered another power supply from newegg but I decided to tool around with it again a few minutes ago and noticed a clr cmos button on the back of the case. I've yet to replace the hardware and try this but I've found out if I hold this clr cmos button down and power the pc on it will stay on. Releasing the cmos button shuts the pc down again though and restarts the on off cycle. I've done this twice but with having no experience in this area I didn't want to experiment further for fear of damaging something. My computer specs are as follows feel free to request any information you feel would be helpful.

Processor- Intel core I7 960 3.2 GHz 8M L3 Cache
HDD- 500GB SATA-II 3.0GB/S 16MB Cache 7200RPM
MOBO- (3-Way SLI Support) GigaByte GA-EX58-UD5 Intel X58 Chipset
Memory- Kingston HyperX (2GBx3) DDR3/1600MHz Triple Channel Memory
Power Supply- 950 Watts CyberPowerPC Power supply
Video 1- ATI Radeon HD 5770 1GB DDR5 16x PCIe
Video 2- ATI Radeon HD 5750 1GB DDR5 16x PCIe

 

Spiz

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I did this but the problem continues. Do you think the new power supply could fix the problem?
 

d_kuhn

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I've had it happen and it wasn't the PS... I ended up replacing the mobo. You might also try reseating your memory... or trying different memory, a buddy of mine had the same thing happen and it was a bad memory stick.

 

Spiz

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Thanks thats what I've decided as well that its either the mobo or the Power supply. I've tried each memory stick individually. the only reason I'm leaning towards power supply over mobo is that it does not stay on long enough for any beeps.
 

Spiz

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If the problem does end up being the mobo, does anyone have some advice on a good replacement for the GA-EX58-UD5 I have in there now? it seems to be out of production.
 

Spiz

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I hooked up the new power supply today and now it doesnt even go the the on off cycle. I used the paperclip test on the new power supply and it will turn on. so I am assuming that this has to be the motherboard. I would just like some second opinions before I sink the money and time into a new one.
 
Work systematically through our standard checklist and troubleshooting thread:
http://www.tomshardware.com/forum/261145-31-read-posting-boot-problems
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.
The following is an expansion of my troubleshooting tips in the breadboarding link in the "Cannot boot" thread.

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-breadboarding

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=youtube_gdata

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.