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Wont power on but case lights are on

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February 12, 2012 7:08:03 PM

i have a desktop that will not power on i have a msi p67a-g43-(b3) and a core i5 2500k it was working a day ago then i put a v6 gt cooler master 200+ watts i have a 512 graphics card and Intel pro 1000 nic and a 750 a-power power supply the only thing i get when i try to turn it on is two blue lights in the front of the case and it doesn't even power on i tested my power supply i am starting to wonder if my motherboard has gone bad can you please help me give me some information to help me out please? :( 

More about : wont power case lights

February 12, 2012 7:32:02 PM

i would first check to see that the cpu is seated properly. if you removed the motherboard, take it out of the case and try powering it on outside of it.
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February 12, 2012 7:42:25 PM

i built it over a few months ago and it started when i changed out the heat sink and fan i don't know if it messed anything up or not
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February 12, 2012 8:10:40 PM

sometimes overtightening the cpu cooler can bend the motherboard and/or the backplate can make it go crazy. try loosening up the cpu cooler just a little bit. otherwise take the motherboard out and try powering on the system outside of the case
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a c 122 B Homebuilt system
a c 144 ) Power supply
February 13, 2012 1:47:26 AM

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 no luck, continue.

The following is an expansion of my troubleshooting tips in the breadboarding link in the "Cannot boot" thread.
http://www.tomshardware.com/forum/261145-31-read-postin...

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 (standby power supply): 5 volts always on. The green wire should also have 5 volts on it. It should go to 0 volts when you press the case power button (this is also a good way to test the power switch and the associated wiring), then back to 5 volts when you release the case power switch. Tolerances are +/- 5% except for the -12 volts which is +/- 10%.

The green wire should be 5 volts whenever the PSU is plugged in and the PSU switch is on. It will drop to about 0 volts when the case switch is pressed and go back to 5 volts after it is released.This will also test the case power switch.

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 (unless you have on board graphics available). In that case, remove any card and connect the monitor cable to the motherboard connector.
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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February 13, 2012 2:06:10 AM

i did what you said and it worked it runs as good as new i can't believe i overtightened the back plate i won't make that mistake again thank you so much!!!!
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February 13, 2012 2:39:36 AM

no worries man. that's what were here for. i did the same thing a long time ago. and now YOU know. and knowing is half the battle. LOL. glad we could help
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