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I just finished assembling a desktop for the first time. The specs are:

  • Gigabyte GA-H55M-S2H motherboard
  • Core i3 530 CPU
  • 4 GB DDR3 RAM
  • 1 TB SATA hard drive
  • 500 Watt PSU

As soon as I plug in the computer, the "phase LED" starts blinking orange and the system fan LED blinks while the fan "twitches". This continues until about three seconds after I unplug the computer.

This worries me a lot because I haven't even turned the computer on and it continues even after there is no power.

I did make sure the PSU is on the proper power setting.

What is causing this and how can I fix it? Is the motherboard dead?

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About the 3 seconds after power bit. This is because the capacitors in the PSU keep discharging even after you unplug it for a few seconds... – Earlz Mar 21 '10 at 15:46
@earlz: Is that bad? Is something fried? – Zifre Mar 21 '10 at 15:48
no, that is normal. I have many computers that continue to have the LEDs and such lit about 5 seconds after being unplugged. So that much you don't have to worry about. I have no idea about the twitches and other issues though – Earlz Mar 21 '10 at 15:50
up vote 2 down vote accepted

I searched around the Internet some more and I found the problem. The connectors for the LEDs and buttons from the front of the case were connected backwards.

The motherboard clearly states which pins are positive and negative, but the connectors don't. They do, however, have a little arrow near one pin. Based on how some other connectors attached, I assumed that the arrow was for the negative pin. It turns out that is for the positive pin. I switched everything around and it works nicely.

My guess is that the actual problem was caused by the power and reset switches being plygged in backwards. I don't know how this actually caused the problem, but the computer essentially acted as if it were repeatedly being turned on for one tenth of a second and then off for half of a second. This leads me to believe that the power and/or reset buttons caused the problems.

So, the lesson to be learned is that when there are arrows on the connectors, they are for the positive pin. Ideally, they would just use plus signs, which would be a lot more obvious.

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Nice to hear you worked it out, but I doubt the polarity of the connectors was the problem. The power and reset buttons are momentary switches which have no polarity and the LEDs simply don't light up if connected backwards. Perhaps you had an LED cable on the power or reset header... :b – efotinis Mar 21 '10 at 22:08
I'm pretty sure it was the power and/or reset buttons. I took each connector out one at a time and reversed it, so I'm pretty sure that I had them in the right places, because it all works now. Also, the LEDs that were blinking were not the front panel LEDs that I plugged in backwards. (It was the motherboard LEDs.) – Zifre Mar 28 '10 at 23:54

I had an identical problem and I thought I would share my fix. I noticed that my 24-pin mainboard power connector wouldn't click in the motherboard slot when I was plugging everything in, but didn't think anything of it. When the power supply was plugged in and switched on, LEDs would flash and fans would spin up and stop over and over.

I replugged the front connectors although I had them in the correct orientation and location, and when that didn't work, I removed the 24-pin connector. When I plugged it back in with no small amount of force and switched the power supply on, none of the fans or LEDs flashed (my motherboard doesn't have a mboard status LED, just a CPU status LED) which nearly made me panic thinking I somehow cracked the board.

I took a deep breath and hit the power button for shiz' n' gigs. Worked.

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