top half of screen dark

Dear all,

Can anyone give advice on how to fix the following? I have a Apple Cinema Display M8149 connected with and ADC-DVI adapter to a Mac Pro or MacBook Pro. Some time in the past the top half of the screen suddenly turned low in luminosity, right trough the middle of the screen. It still show an images but darker than the bottom half. So the top-half has half the luminosity of the bottom half. Feels like some fuse issue? Or maybe something else? Can anyone identify this problem and advice how to fix it? I ruled out the adapter (same problem with a new one) and the graphics card (same problem with different computer setup ). All help is appreciated!

Kind regards,

Marcel