welcome to Just answer
Please tell me its complete model number
and how old is it ?
so the problem is there even when you connect a DVD player to the TV ?
OK and what about the sound ?
Is it completely fine ?
Is there a glow to the screen or is it completely dark ?
I mean if you look at the screen in a dark room
OK the problem is most likely with the Inverter board of the unit that is bad and will need replacement
the power supply seems to be working fine
best is to contact Samsung for the part