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Computer comes on then off

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December 21, 2010 2:59:01 AM

Hi,

I used ATI's Extreme utility to try and overclock my HD2600 slightly. The recommended settings were 600 for the clock core (normal speed) and 480 for the memory core.

As I was playing, artifacts showed (which I have read about) but my stubborn nature lead me to keep the settings recommended by the utility. The display froze completely and the computer switched off.

Now the computer comes on for fans to start spinning, very briefly, then goes off quickly.

I have replaced RAM sticks, took the video card out of course, and even replaced my processor thinking it was that. I have also replaced the main hard drive, taking out the slave-drive, with a back-up window installation (with nothing else on.) I took all other peripherals out.

My PSU is an Antec Earthwatts 380.

Do you think the motherboard has short circuited? What, in your experience, could the cause of this be? Would the removal of the battery (or the adequate jumper settings) help?

Thanks as usual boys an girls

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a c 156 V Motherboard
December 21, 2010 10:42:54 AM

Work 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.

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 or long single beeps indicate a problem with the memory.

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.
December 21, 2010 9:27:51 PM

Thank you for your very detailed answer. Forgot to say that my CPU socket is 478 pins and my motherboard is a GA-8S655FX Ultra.

I have tried almost all of what you have said, except for breadboarding as I don't really have the possibility to do it (no space.)

I have taken the CMOS battery out and put back in. The computer turns on without switching off this time, but it sounds like it's in a loop; the drive spins and clicks then after a while the system emits a long beep (Award Modular BIOS.)

All connections are firmly attached, CPU fan works, the computer has power. All card have been taken out, PCI audio-card, AGP video card. There is no onboard video chipset. RAM is firmly in place.

I will try a different PSU (the original PSU of an OEM system which has only the case of the original system, as all components have been replaced including Mo/bo)
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a b V Motherboard
December 22, 2010 1:37:30 PM

Do you have an additional video card you can try?
December 22, 2010 8:54:50 PM

Allright there, I've tried my Radeon 9250 but it has much the same result. Oddly, my monitor won't come on either (checked the plug fuse etc). I think something fried both the Mobo and the monitor, never happened to me before.
!