Chosen Solution
I have a mid 2007 intel iMac 20" that won’t power on. When I plug the ac adapter in the first led comes on. When I press the power button led’s 2 and 3 come on and the fan spins at regular speed and the optical drive starts up. Led 4 never comes on so I think its an LCD or video card problem. Do I need to test the Psu or is it the logic board or the video card? Thanks in advance!
Try plugging in an external monitor, it could be the inverter… if nothing shows up, its the logic board. It would be unlikely that the problem is the PSU as your computer does start up and shows LEDs (which means it can process.. to an extent)
