Chosen Solution
I replaced the thermal paste of my iMac as it has been getting very hot lately. Once mounted, the computer no longer turns on: no sound, no fan … dead. Diagnostic LED # 1 is on, all others are off. I replaced the power supply but nothing has changed. I tried to remove the Ram, the button battery, reset SMC but nothing, it doesn’t want to turn on. Logic board dead, CPU dead? How can I understand what’s wrong?
You’ll need to go back to your CPU. I’m suspecting its not properly mounted and/or the pins in the socket are damaged. Make sure you have the chip correctly placed and when you tighten the screws you follow the proper technique to tighten them. Think how you mount a spare tire going back and forth across the lug nuts so you mount the rim evenly. We need to follow this same approach! once the screws are snug you need to torque them evenly as well and to the correct value.
