Replace the power input cable. May help, can't hurt. Look for any signs of being burnt.
The cable that goes from the wall socket to the power supply.
Make sure it is a cable designed for a power supply and not a video screen. They have the same ends.
My power supply cords are either 14 or 16 AWG. This is found on the cable.
The smaller cables are not rated for the proper amps.
American wire gauge - Wikipedia, the free encyclopedia
My 2cents worth take a look at this and then test the volts at pin 8 (grey) on the 24 pin if this voltage fluctuates lower than 2.4 or higher than 6.0 volts then the PSU self test is failing and the PSU is faulty.
http://www.tomshardware.com/reviews/power-supply-specifications-atx-reference,3061-2.html
see Power_Good in section 2.
PS Use a digital multimeter not the analogue type RED lead pin 8 BLACK lead any black pin or even the board fixing screws.
It might even be worth testing the resistance between a black 24 pin lead and the board fixing screw. So set to resistance (OHMS) and touch across the machine ideally should be shut down and should read zero ohms.
Unplug all PSU cables except the 24 pin and 4 pin atx mobo cables. If it still powers on for just a few seconds it's probably a short in the mobo.
The green motherboard light means it's getting power, but doesn't mean the motherboard is working.
Pull out the RAM sticks, then try one stick at a time. See if it will start.
You can also, take the CPU to a shop and have it tested.
Perhaps, some of our others members will have more suggestions.
Mate try leaving the 24 pin in and just test the cables to the CPU and GPU etc etc if there is no volts coming through then that may indicate that the CPU (or the GPU) is getting no supply.
Do you get any beeps at all on power up? Maybe the RAM is shot might be worth trying this.
MEMTEST
https://www.sevenforums.com/tutorials/105647-ram-test-memtest86.htmlthis one you will need to make a bootable disk set the BIOSto optical (or USB if preferred) boot the machine and let it run for at LEAST 8 passesunless the errors come upstraight away. Takes a fair time to complete and some leave it runningovernight.
If you do get errors and have morethan one stick then you will need to test each one separately and maybe even inthe separate slots.
Not sure this will help, but I would try it before I replaced the Mobo. Shutdown and disconnect the power cord. Wait for about 20 seconds.
Remove and replace the CMOS battery and restart your computer. This will start you off fresh as with a new build.
It is a lot of work, but not so much if it works. Hope this helps.
For what it is worth I had the same thing happen a couple of years back. First thought was PSU. Didn't help but needed better on anyway. We were travelling around the Yukon and Alaska at the time and really needed the computer. Desperation says WTF can't do any worse,(maybe) so I tried removing all the cards on mobo, tuners, video etc. Obviously with video out nothing is visible but lo and behold, a miracle. When powered on the HDD active light is keeping its flash a second seek light going. Put cards in one at a time and it was the video card killing it. Found new video card (this part hurt) $125 for a cheapie that cost $37 in Calgary but beggars can't be choosers and it worked perfectly for the rest of the summer.
This may or may not help you but the price is free. Good luck,
Art.
I just dealt with a power switch problem on one of my computers. To test if the motherboard headers were working correctly you can jump the circuit without the power switch (carefully with a screwdriver). I fixed the issue by going to radioshack and buying a momentary power switch. Any momentary power switch should do because all your doing in connecting a circuit. I cut off the old switch and wired on the new one. Computer works great now.
It's been a few months but I'm back! I've finally purchased a new motherboard and CPU. My problem now is the hard drive isn't booting. "reboot and select proper boot device. I've tried everything to get into BIOS but no luck. Would I need to purchase a new hard drive to work with a new mobo/cpu?
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