But let's say you bought in in the USA and went to another country and there is no warranty for that. The following is fairly generic so I'll write it here:
Let me lead with this sort of work is going to have us getting into areas that can be dangerous to LETHAL. With this warning out of the way let's continue.
If this was mine I'd get the back cover off and try the most common free simple thing. Ready? With the power removed and waiting for voltages to drain and even then practicing safe electrical practices (which I will not write here as that is up to the tech or repair persons) I would:
1. Remove connections and power to the set.
2. Remove the back cover (see youtubes on how.)
3. Gently unplug and re-plug all connections.
If that doesn't help then it's one of the board or panel failures. Panels cost too much so if you find it's not fixed with the usual boards (TCON, main board) then you send the set to the recycle center and shop for a new set.