Power supply not working in my new build

[Schooly]

Hi , I have got this components:
- intel core i5 2400
- Asus geforce gtx 550 ti
- gigabyte z68xp-ud3
- Gigabyte powerock 500 watt
- seagate 1 tb
- (2×4gb) kingston rams

after i assembled all the component in the case , it worked for i while and then stoped working at all
no power comes from the psu , so whats the problem ?
* sry 4 ma Eng

 

[l0v3rboi]

What do you mean by no power is coming from the psu? No boot? PSU does not light up when turned on?

 

[Schooly]

in the first time fans spin, lights come on for a sec and turned off then in the next times ther's no boot

 

[Schooly]

????