Panasonic Quintrix 32 old tv, no display?

Hi
My panasonic Quintrix old tv has suddenly stopped and after that no display is coming up, only the black screen. what might be the problem.

Yesterday while watching we turned off the set top box but not the TV, so it ran for 15 mins with out any program just those white dots all over the screen, which is normal. after 15 mins it stopped, we thought it went to sleep mode or power save mode. But i could never turn it on again, always the black screen.

Thanks
Srini