4th LED on logicboard is not on
I am experiencing the same issue, at first the iMac froze and then i proceeded to shut it off. Then, I turned it back on and there was no chime, picture, or even a back light from the LCD but I could hear the fans and drive spin up. I took the iMac apart and checked out the LED's the first LED lit up after plugging it in, the second lit up after turning it on and then the third one turned on shortly afterwards, then they all turned off and then came back on again.... but the fourth never lit up at all during this process. I would assume the logicboard is at fault due to the nature of it not giving me any visuals and or post chime. I know that sometimes when PSU's go bad the internal fans and drives can still turn on if they are operating on a separate rail. It's either of the two I just cant figure out which one.
Is this a good question?