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Need expert help on new computer build - no power

Last response: in Motherboards
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July 1, 2009 12:32:43 AM

Hello all. I am building my first PC from scratch and am having a hell of a time with it.

Here is what is happening.

I have 2 motherboards and 2 power supplies. Both power supplies test ok with an ultra power supply tester and when they are plugged into the tester.. the psu fan spins and lights up.

When I plug the psu into the mobo via the 24pin connector and the 4 pin connect I get a led light on the Asus mobo but the psu fan does not light up. I press the on button which is connected according to the instructions that came with the mobo but nothing happens.

So basically 2 mobos and 2 psu's later.. still no power to the case/psu.

For troubleshooting I have...

- tried a brand new psu
- tried a brand new mobo
- tried brand new mobo with brand new psu
- removed power switch from pc and installed it into known good pc and it worked fine in that one but does not work in the new build.
-tried to connect new psu to mobo out of case on top of anti static bag and psu fan did not spin after I click the power switch.
- cleared the cmos settings and removed/replaced cmos battery.

What am I doing wrong? Is there something that I missed? Could I have fried 2 mobos? If so, how do I prevent frying a third?

When I installed the screws and standoffs I did not use washers because non were supplied with the kit. I did however use an anti-static strap.

Thank you for your help.
a b Ĉ ASUS
a b ) Power supply
a c 435 V Motherboard
July 1, 2009 1:35:28 AM

Be sure the power supply toggle switch is in the "on position" in the back of the power supply. Double check the power switch pins; I've sometimes used the wrong pin cluster when connecting those case leads. If your power supply 24 pin and 4 pin (or 8) are connected to the board, then you should get some startup noise when you touch the power switch pins with a screwdriver. I just move the screwdriver around the whole cluster until it fires up; touching the wrong pins won't hurt anything; all the pins in this cluster are low voltage. Finally, be sure your board bios supports your cpu; some boards require a bios flash and won't post with certain cpus until this is done. You can use an older cpu and maybe asus "crashfree bios" software which comes on some of it's motherboard cds. I've never tried it. Consult your board manual to see if your board came with it, if you have asus. Another point is to always post your system specs before asking any question.
a b Ĉ ASUS
a b ) Power supply
a b V Motherboard
July 1, 2009 1:37:15 AM

Instead of using the power switch . . . remove its connector from the mobo, and simultaneously touch the two pins you *think* are correct with a screwdriver. This does what a working power switch does, ie, makes a momentary contact.

If the board fires up, your switch is bad.

If not, the board is shorted somewhere, bad, or you have the wrong two pins.

Short: Remove the mobo from the case, place on a non-conductive surface, like the box it came in. Hook up the psu, and do the screwdriver thing again. if it works, reassemble board in case more carefully :) 

Pins: Try putting the screwdriver on the right pins :) 

Still no go, some kind of mobo problem.
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a b V Motherboard
July 1, 2009 2:30:53 AM

Do not rely totally on whether or not the CPU fan spins. Make sure you have the heatsink fan connected to the correct plug on the board. Start with 1 stick of memory, and the video card and see if you can get the board to post. My old DFI socket 939 board would not spin up the CPU fan for a full minute or so after you first powered-on. Most fans will spin at first, but not always!
July 2, 2009 7:30:10 PM

Thank you all for your help. I took it all out and found a missing standoff. Everything works now.
!