Quick follow up for anyone who's interested. On Friday I installed a replacement logic board. The iMac came back to live and for the first time I heared it chime. Right after that, the fans started spinning at full speed and the display didn't came on. I asked the seller of the replacement logic board about this and it appears that he gave me a logic board for the middle range model, which needs a dedicated graphics card I don't have.
I am now looking to buy another replacement board with the integrated NVIDIA graphics card. Hopefully the machine runs fine then!
I am now looking to buy another replacement board with the integrated NVIDIA graphics card. Hopefully the machine runs fine then!