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Comp wont turn on !

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December 22, 2010 6:50:07 AM

Hi there I have a problem my computer that i just built today (22 december 2010) .. I pretty sure I put everything together properly...wen I try to turn on the computer it doesnt turn on. I connected all the power cables accept for the one that says power LED which is for the power button light not the actual power switch... i dont know wat else to do ! any help/suggestions will be much appreciated .Thanks

Specs:
CPU : AM3 x4 640

MOBO : ASRock 880GMH-LE-USB3 880G USB3 DDR3 Motherboard(on board graphics)

RAM : 2GB PQI 1333Mhz

HDD: Hitachi 3.5" Deskstar 500GB SATA HDD

CASE: Thermaltake V3

PSU: Came with case all it says 450w


EDIT : i forgot to say that when i press the power button the case fan starts up( it LED lit so the light comes on) and the heat sink fan starts up but only (literally) for a second then stops.

but when i try to start it up again nothing happens :(  :( 

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a b B Homebuilt system
December 22, 2010 10:45:03 AM

First, disconnect everything (including ribbons, SATA cables, all power inputs to drives)internally except:

CPU (make sure cpu aux power input is connected to mainboard)
one stick of mem
video card (enure video card's supplemental power input is connected to card)

If still won't post, PSU is usually a viable suspect...
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December 22, 2010 11:28:37 AM

thanks dude. ok did that but still doesnt do anythin! ......i only have one stick of RAM ....and im not sure wat u mean bout the video card ...i dont actually hav one ...its onboard graphics ( HD 4250) ??

oh and the hard drive LED lights up wen i turn the power on but the PSU fan doesnt start to spin or anythin...
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Related resources
a c 122 B Homebuilt system
December 22, 2010 12:14:10 PM

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.
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December 23, 2010 10:40:43 AM

THANKS guys .. i hav very gd news ...computer is workin !!! it turns out that the PSU was the cause....wen i turned on the comp the PSU made a loud POP sort of sound & i saw sparks ( i think) and then somethin smelt like it was burnin.....so i took it back to the store where i got it from which they did with no hesitation after they tested it which had just tripped the electricity !!! lol so thanks again guys
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December 23, 2010 10:41:12 AM

Best answer selected by chocobaby.
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