Backlight wont work Sony Vaio SVE1512C6EW?

Hi there!

I have changed the screen and lvds cable on a Sony Vaio which had a broken screen. But still the backlight wont turn on.

It works on an external monitor, and you can see the screen is working but with no backlight.

Both old and new screen is almost completely black, so its not likely that the screens are broken. And yeah, two different cables and still no positive result.

Is it the motherboard, or something else?

Any Ideas?

Help is much appreciated