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PC wont turn on

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  • Homebuilt
  • Power Supplies
  • Systems
Last response: in Systems
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August 20, 2010 6:12:57 AM

I just finished building my new computer and it wont turn on. The LED fans blink and the fan moves for a few mili-seconds, the CPU fan and graphics card's fan jerk for a milisecond. I think it is the power supply because when i plug in my cold cathode lights which just plug into the power supply with no mobo plug in they do not work. I was wondering if the case could be the problem as well, I double checked to make sure the power, hdd, power switch were all plugged into the right spots on the mobo. I am very frusctrated, any help would be much appreciated.

Thank You

More about : wont turn

a b B Homebuilt system
a c 104 ) Power supply
August 20, 2010 6:23:29 AM

Have you got another psu you could test the rest of the system with?
or a multimeter to test the psu?
if you post full system specs, people can help a bit more too,
Thanks
Moto
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August 20, 2010 2:28:32 PM

CPU-i5-760
MoBo-p55-ud3
CASE-Modtek Cassini
PSU- SilverStone SAtrider Essential Series 500w
GRAPHICS- Engt220
HD:1 TB Western Digital, Caviar black 7200rpm, 3gb
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a b B Homebuilt system
a c 104 ) Power supply
August 20, 2010 2:31:15 PM

Ok, when you built it, did you install the standoffs correctly?
if so, proceed to checking the psu out,
must sleep, back later :p 
Moto
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August 20, 2010 2:37:33 PM

Standoffs all in correctly
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a c 122 B Homebuilt system
a c 144 ) Power supply
August 21, 2010 3:45:24 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.

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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