Samsung LA40C530 LCD Backlight problem

[provider10]

Hi All

Hope you can help . Got this Samsung LCD TV LA40C530
Problem is with the backlights that intermittently switch off. They can be ok for more than 8hours, then next day only stay on for a few minutes.
When they are off all voltages seem to be ok on Psu the BLu-on is OK.

Any Ideas

Thanks

James