Power not comming

[aravinda]

i've a gigabyte z77 dh3 m/b. some times when i try to turn on the cpu, power not working. that means power not comming via m/b. power supply working correctly. after i reset bios( remove the m/b battery) then power comes. please if you help me i would appreciate it very much

 

[aravinda]

How do you know that the PSU is working correctly?[/quotemsg
becouse when i reset bios, power comes.
but i'm not sure
can u plz tell me what should be the main cause of this problem.