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Motherboard won't turn on. Expert needed, please help.

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January 20, 2009 7:46:51 PM

I just hooked everything up, the motherboard LED goes on but when I flick power switch nothing happens no fan. Power switch is hooked up properly, not even graphics card fan will work. The power supply should work 465 watts. It isn't shorting out either, im sure of it. I put 1gb ddr2 ram stick 667 and a am2 athlon x2 5200 cpu Brisbane. It is a M2V motherboard, it isn't mine and im depressed now I need it back by tommorow. Please help :( 
a b Ĉ ASUS
a c 229 V Motherboard
January 20, 2009 8:32:11 PM

Just to make sure, in addition to the 24-pin power connector, you didn't forget to connect the 4-pin or 8-pin CPU connector?
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January 25, 2009 8:26:53 PM

Yeah, I have a 24pin powersupply + a 4pin connector and they are both hooked up. I noticed it is pretty warm by the ite
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a b Ĉ ASUS
a c 229 V Motherboard
January 25, 2009 9:15:13 PM

If you connected the 20+4 (24-pin) ATX connector as well as the 4-pin ATX CPU connector (the small 4-pin socket closer to the CPU) and it won't start, then connect a speaker (if you haven't already done so), remove everything but the CPU and power up again. Does it beep to indicate that memory is missing? Is the CPU installed properly, i.e., are you there are no bent or broken pins (if it's possible with that CPU)?
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April 26, 2009 3:48:09 PM

If you have a motherboard that won't do anything when the power button is hit and everything else looks normal, try replacing the CMOS battery.

I just had a ASUS board which showed the green LED for power, but did nothing when turned on (shorting the pins on the board also). The CMOS battery was showing less than .5 volts and replacing it restored the startup. I assume the battery voltage is used as a reference so when it drops below a certain level, the power cannot be verified and therefore not allowed.
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April 22, 2011 11:19:59 PM

Hi Saltgrass

I bought the Asus P5N32-E SLI about a month ago and installed it with a 400 watt PSU and it worked fine. In fact the PSU is an old one without the full set of power pins on the connector and also only has one 12v plug so I had to leave the other without a connection. According to the manual though this would still work, and it did.
The other day I went to plug my headphones into the front audio jack and the machine just died, powered off. I know the computer was wired correctly as I do this for a living and have double checked it and found no problem.
I did as you suggested and tested the CMOS battery and found it to be as dead as a dead Dodo! I have replaced it and other than the green light illuminating, it will do nothing.
I have put it on a more modern PSU with the full set of power pins although I still only have one 12v plug and now the green LED flashes instead but it still will not power up any further.
I dont really want to buy a new PSU as I know this should work with the ones I have. I have also tested them with my PSU tester and they are showing as working correctly.
Any other ideas?
Thanks alot

Phill.
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a b Ĉ ASUS
a c 156 V Motherboard
April 24, 2011 12:04:38 PM

You need to be aware that PSU testers put only a minimal load on the PSU.

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 not, continue.
The following is an expansion of my troubleshooting tips in the breadboarding link in the "Cannot boot" thread.

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: 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, 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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Anonymous
a b V Motherboard
April 25, 2011 9:23:42 AM

Hi just read your post it sounds like the power supply is not giving enough juice to components u need to get a new power supply but before u do is there anychance u could borrow one from your friends to try first ,plus if it is psu i would recommend buying minimum 500 watt
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May 3, 2011 10:57:18 AM

I agree with the previous poster. I cant tell you how many repairs I have administred just by replacing a power supply that either is very poorly made or just not enough power to the system board. Most of your multi-core processor require no less than 500watts. I would advise no less than that. If your running multi hard drives, and multi video card 700-1000watts.

Hope this help.
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February 21, 2013 1:00:03 AM

In case anyone else reads this post. I had the same problem. I discovered that I had put the male side of the CPU power cord incorrectly into the mobo. If you look closely you'll see that some of the sides on the male end (the PSU cord) have curved edges, these should be matched up with the curved edges on the female side on the mobo, if they aren't then it's as if the cord isn't plugged in and the machine won't power up.
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