Chosen Solution
Hi everybody, My 2017 21.5” iMac 4K has serious logic board problems for about an year now. At the beginning things were tolerable but now the freezes, the inability to turn on the computer except after doing about 10 on/off cycles are making it almost unusable. I’ve diagnosed it and it seems I have to replace the logic board. I don’t want to spend more than the computer cost on the new logic board and they are difficult to find anyway. But I’ve found a logic board from the non-4K version of this iMac for a pretty good price and locally. Having in mind that as per the ifixit video the processor and the graphics chip are modular, is it possible to just use this logic board on my iMac and just move the CPU and GPU to it? Looking forward to your answers. Cheers!
You can’t use the non-4K logic board with your 4K display ;-{ Basically the 4K board uses a different display cable than the non-4K models as it needs more signal lines to push the display as you can see here:
So basically you need to replace your logic board with the correct one. Sorry ;-{
