Chosen Solution
Hello, my imac 21.5 inches of 2010 emc 2389 does not start anymore after a repair of the graphics card, it is not the first time that I make a repair on an imac but I am stuck … When I press the power button nothing happens and more amazing no diode LED is lit! When I plug the cord the LED # 1 lights up briefly then goes out after 5 seconds it turns it on again then nothing. No fan turns, no sounds nothing is nothingness … I tested my power button with the multimeter and it works. I tried to reset the SMC several times but no change … I went around a lot of forums, and try a lot of things, I also have all disassemble and go back several times … I tested the multimeter the voltage output of the power supply, I have the tensions shown on the forums … I even tested on the card side of the motherboard so a priori there is good juice … Especially since the power supply worked perfectly well before the repair of the graphics card. I even try to remove all of the motherboard and plugged only the power supply but it is the same at the LEDs If anyone has ever had this problem please share your experiences …
Sounds like you have a bad AC connection or short as the onboard diagnostic LED#1 should be on when you have AC cord plugged in. I would start off making sure the AC outlet is OK using a outlet tester like this one Power Gear 3-Wire Receptacle Tester, next I would try another AC cord to eliminate the baseline. As you had serviced the system I would go back in and make sure you didn’t mis-connect a cable or damage something or pinched a wire. Once you’re sure I would get another power supply to see if that made a difference.
