Windows 7: monitor black screen problem

I am having a problem with my samsung tv/monitor.

in the middle of my usual work on computer my monitor went black screen, computer continued to work normally cos i was hearing it on speakers.
also red led on monitor stayed as it work normally.
i restarted monitor and picture came up for 2-3 seconds and monitor went black again.



before you get me answear that cable causing the problem
this happend also when i try to watch TV. when its not connected to Pc. via cable cos this monitor has a tv tuner also.
so i switch source to tv. picture came up for 2 seconds than went black...

I tried to search samsung troubleshoot page for solution but didnt find any simular problem