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hey guys thanks for your help...but i still have the same problems.. well first of all my psu is an antec 420 watts, i got it at new egg, i decided to get that one because i wanted to plug a lot of stuff to it, but anyway i have only conected the motherboard to it, and still doesn't want to work, i cleared the cmos, tryied starting it up with no ram, no hd conected no cd unit, no fans, still the same problem motherboard lights up cpu fans spin for 3 seconds and then it shutsdown, i decided to get a whole new set up from a friend a gigabyte motherboard a northwood cpu different set of ram and i get the same problem!!!!i am thinking that it has got to be the psu, maybe it nees a lot of power to run and my apartment doesn't support it??? maybe it is a defective psu????? i don't know guys ,if somebody canget me a ny ideas , thanks!!!!!
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Is it the true power? Make sure you don't have something (besides a fan) hooked up to the "fan only connection". I didn't realize this till I was reading the manual last week but that connection will actually cycle down up to three case fans when not under load in order to run quieter. If you plug your optical drive or hdd in to that connection it wouldn't work properly. There is also a three pin connector with that power supply that will do the same for your other three pin fans plugged into mobo (cpu and otherwise I believe). Also if I am not mistaken it is possible (don't know about your specific mobo and all this is a shot in the dark) that the ps is cycling down your fans so low that they are tripping the threshold set in bios and shutting your comp down.
Actually, I think I know exactly what is wrong buddy....your psu isn't on. Make sure the switch on the back is turned on. Once you turn it on you shouldn't have to mess with it unless you have to do a cold boot and control-alt-delete or you case reset doesn't work. Don't ask me why it cycles up the fans at all if the switch is off but I had it happen to me in the past so I know it does....
If it isn't that double check your case to mobo connections maybe...
if that doesn't work maybe it is defective like you were thinking..
hope it helps
<font color=black>yippie ki ya, m..........<font color=black>