Personally tbtkdz,
I wouldn't get mucking around inside a modern TV set.
They run at half-mains voltage these days, on the chassis itself, the un-wary can get a very nasty surprise, not to mention the risk of the EHT (14kV+) side of things!. [Linked Image]
My advice would be take it to a TV repair person, they are in the "know" and can locate the fault simply and a lot quicker than what you possibly could, they have a lot of specialised test gear for this sort of thing.
I guess it's just one more reason why I'd never buy a thing like that without seeing it operating properly before I handed over the cash.
Just my $0.02 worth. [Linked Image]