iMac 2010 No display on internal lcd only black screen

I have a 2010 imac

It had a faulty connector, connector has been replaced

But there is no display

The screen lights up black but no image

So backlights are working

Tried the lcd on another imac lcd works fine

As does the gpu

All 4 leds light up too.

It outputs to an external lcd fine

At a bit of a loss here.

somethign on the logc board does not seem right.

But what