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I shut the computer down and then when I go to turn it on it powers off

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August 21, 2010 2:44:03 AM

Hello,
this morning I shut down my pc after using it to give it a break for the day. When I tried to use it later it wouldn't stay powered on. It turns on and then off before it boots. What's wrong, it was working just fine in the morning before I gave it a break and shut it down
August 21, 2010 3:03:35 AM

I had this a couple of days ago.
Try these:
Remove ram and put it back in
The atx cable( the one coming from power supply straight to motherboard and long and rectangular) try pushing it in more, it may have slipped out(worked for me)

Take out any USB storage devices( for some reason can screw up boot)
Ensure graphics card is inserted properly and the power for graphics card

Make sure the CPU fan power is plugged in, usually in top right corner of motherboard( not the 3 pin one)( it comes straight from the power supply)

And yeh try those and get back to me
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a c 144 ) Power supply
August 21, 2010 6:23:54 PM

axxeon said:

Take out any USB storage devices( for some reason can screw up boot)

Make sure the CPU fan power is plugged in, usually in top right corner of motherboard( not the 3 pin one)( it comes straight from the power supply)

USB - some motherboards will refuse to boot with a flash drive inserted. Some don't.

OP's system was working, then not. It's probably not because of the fan header. OTOH, it doesn't cost anything to check.

kathy, your motherboard or PSU could have died. System specifications?

Anyway, it's time to start troubleshooting.

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.

Breadboard - that will eliminate 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. You do have a case speaker installed, right? If not, you really, really need one. If your case or motherboard didn't come with a system speaker, you can buy one here:
http://www.cwc-group.com/casp.html

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:
At this point, you can sort of check the PSU. Try to borrow a known good PSU. 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...

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.

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.
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