Gigabyte K8NPRO-SLI and instant power failure

[grtmoby]

I have a very strange problem and think it is a defective mobo and ask for your advice. I have a system consisting of the Gigabyte GA-K8NPRO-SLI, Aspire 550 Watt, 2GB Corsair XMS, Maxtor 100GB SATA, BFG 6200 and an LG DVD-RW.
All was working fine till suddenly i needed to press the start button 2 or 3 times till the system catch up and start, when it does everything is more than perfect. Today the system won't start, i press the start button and the processor fan start to turn but suddenly the system will shut down. I have no extra cards or devices connected to the mobo but still no luck.
I tried the power supply on my other computer and it worked fine with no issues but the other computer is an AthlonXP and so it uses the 20 pin power connector not the 24 as the new one. Will this has any influence or not.
Any help guys if this is a defective mobo or another way to test the power supply. please help me.

Thanks in advance

 

[fishmahn]

First thing I thought of was see if just shorting the power jumpers on the mobo works. Maybe its just the case's switch. (long shot, but easy test and cheap replacement if it is).

A 20-pin will work on a 24-pin socket as long as there's not too much load - you have a low-end video card and an A64, so I would think for testing its' not a problem. If it makes you feel better get a 20-24 pin adapter for a couple bucks.

Your description about the error (fan starts but doesn't continue) points to the mobo's cpu fan header. It may not be getting a signal from the fan that the fan exists, so it doesn't let the system start. I would make sure its plugged in there and reconnect it in case it got a bad connection.

Mike.

 

[smeghead4269]

I've never heard of a Gigabyte board (or at least not a recent model) not starting up because it doesn't find a CPU fan. It might give you a warning during the POST, but it should still start up.

Since you tried swapping out the PSU and the problems went away, I'm thinking that's the most likely culprit here.