Chosen Solution
IMAC 2011 21.5 EMC 2428 It was working perfectly. It was opened to change thermal paste. Now it turns on but the screen goes black after a few seconds the fans accelerate. The diagnostic LEDs light up the 4. Apparently there was no error in the assembly or damage to any cable or board. the machine had no problem with the video card before After reassembly, he presents this symptom. Only the thermal paste of the processor was changed. The video card has not been tampered with. Do you have any tips or details that I may be missing?
More often than not, you likely didn’t mount the CPU correctly. You’ll need to pop is off again to make sure the socket pins are not damaged and when you remount the heat sink make sure you slowly tighten the screws in a cross pattern like you do for changing a tire rim, tighten each screw in a star, or criss cross, pattern.
