I replaced the NVIDIA 130GT w/ a 4850 AMD Radeon card from a 27" imac, same year (late 2009). Computer boots, all 4 LEDs go on, computer accessible from remote screensharing on the LAN so is obviously up and running. No picture on the screen (backlighting working).
I think it's an EFI/firmware problem w/ the new card. Any ideas as to a work-around? Edit the BIOS in the GPU to match the 24 inch screen or the Logic board ID? Thoughts? Thanks!