Just finished fixing a broken 20" iMac from 2008. Swapped a faulty videocard for a working one and put the whole thing back together. At first, the display wouldn't come up, suggesting the LCD wasn't properly connected. I fixed this issue by reconnecting the display cables to the logic board. Then, on restart, the display comes up, but the image looks very distorted or some sort. I thought this could be a videocard issue as well, but when I connected the iMac to an external screen, I didn't notice any graphical problems or glitches. The internal display of the iMac did work absolutely fine before swapping the videocard. It does have the curtain effect though, but that doesn't really bother me. Any ideas what this problem could might be? And how I can fix it? I've included two photos down below to illustrate the problem. Thanks in advance for your help!