Converting iMac to ext Monitor, Backlights seem not to be on fully.

Hello, this is my first project so bear with me. I‘m turning a late 2009 imac into a external monitor by replacing all internal hardware with a controller board from vsdisplay.

So far i have:

• Opened up the case and identified the lcd panel (it‘s a lm270wq1-SD(A2))
• Purchased the right controller board (sorry if that‘s not the correct terminology)
• Gutted the imac to make room for the cabling and controller board
• Connected the board to the lcd panel, tested it and for now closed the case back up

The image is clear and sharp as is to be expected from the panel. It takes the hdmi signal and the power supply (a 12V 5Ampere brick) seems to work fine.

There is only one issue in that the image is very dim. I‘d say it‘s about half as bright as it should be. I saw a different post on the forums that also had backlighting issues but that doesn‘t seem to be the same problem since my brightness appears to be homogeneous across the whole display.

Before proceeding i wanted to ask for help.

Here are some images of the cabling, the controller board and the display.