PS Vita 2000 board issue

Hi folks,
I’ve got a PSV2000 and the screen is black but in bright light you can see its working.
It’s like the LCD light isn’t working, so to trouble shoot I’ve plugged a new LCD into it and still the same and I’ve put the motherboard into a known working unit and it’s still the same so the issue is on the motherboard.
Any ideas what it could be and what part I should be looking at???

Thanks for your time👍