Chosen Solution
I have never seen something like this in many years of repairing, diagnosing and building computers. Just had finished taking the mac apart, to clean the fans clogged with dust. Put everything back in place, pram battery as well, now the system won’t boot. It will turn on, the fans are starting, 3 out of 4 leds on, but no chime or image on the screen and no image on an external screen either. I have tried pram and smc reset and it beeps if I will take the ram out. Please advise or it’s going out the window.
Based on the diagnostic LEDs, the display may not be connected properly, or the display or inverter might be broken. For more, look here: Where can I find the diagnostic LEDs on first iMac Intel?
