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Mobo Has Power, Not Turning On Though?

Last response: in Components
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Anonymous
a b ) Power supply
a b V Motherboard
November 4, 2010 1:23:48 PM

my asus socket775 mother board got power but i can not switching on,not power up.what should i do?

More about : mobo power turning

a b Ĉ ASUS
November 5, 2010 7:12:03 AM

The title of this topic has been edited by Buwish
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a b Ĉ ASUS
November 5, 2010 7:12:28 AM

If this is a new build, ensure that the mobo is properly grounded.
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a b ) Power supply
a b V Motherboard
November 5, 2010 2:23:36 PM

I had this problem, and to make it worse the computer would randomly turn itself on a few minutes after I'd stopped touching it.

I'd checked all the buttons on the case, the connections to the motherboard and even tried shorting the pins with a screwdriver, but nothing worked.

It actually turned out to be the power supply itself - pretty much everything was fine to power the system, but the power on signal wasn't getting to the power supply (a PSU tester showed some of the rails were dead).

Swapped out the PSU, everything worked fine.


So, check your buttons, try shorting the power buttons pins directly and also try changing the PSU in addition to buwish's suggestion of checking the mobo is mounted properly and not shorting.
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November 5, 2010 2:36:16 PM

i smell power problems check our psu canyou tell us how old the psu is
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a c 144 ) Power supply
a b Ĉ ASUS
a c 156 V Motherboard
November 8, 2010 1:01:46 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 beeps 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. 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 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...

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. 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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November 9, 2010 3:48:03 AM

nice trouble shooting tips.... O^o
and wheres the OP is he even reading this thread which he started...
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a c 144 ) Power supply
a b Ĉ ASUS
a c 156 V Motherboard
November 9, 2010 10:31:11 PM

Thanks, vada.
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November 9, 2010 11:46:59 PM

I bet it's you PSU. Get a tester or install another PSU if you have one on hand.
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!