Losing picture constantly?

If you can see a faint (but dark) picture - you may need to hunt for the best angle - that could point to a failed backlight inverter. As the other contributor said: It will certainly be repairable but only you can judge the likely cost of repair versus the cost of a new TV - with a warranty.

Alternatively, if you are up against it - why not look in charity shops? The British Heart Foundation do electricals

Such is our throw-away society
February 2016

Clearly your TV has a fault in the circuitry that delivers the picture - it seems to be dependant on how long the set has been on for - a heat related fault - it might be a failing component or a poor joint (which amounts to the same thing).

Sometimes a confident amateur can track down a fault like this with controlled tapping and/or freezer spray. But it really needs test equipment - circuit schematics and experience.

It will certainly be repairable but only you can judge the likely cost of repair versus the cost of a new TV

Amazon offer a 19" TV with built in DVD for under £90

Good Luck...
February 2016