Model A1311 / Mid 2010 / 3.06 & 3.2 GHz Core i3 or 3.6 GHz Core i5 Processor

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iMac doesn't Power ON / No power, no fans...noting


I have an iMac 21.5" 2010 with an i3 3.06ghz processor. Currently when pressing the power button it does not do anything at all no sign of life. I have already verified the power outlet works and tried a known working power cable still noting.

So i opened it up and looked for the LED diagnostic lights, while the power is plugged in all 4 LED lights are off. So i unplugged the power cable and plugged it back in again. LED #1 turned on for about 1/2 of a second then turned OFF.

I looked up the power pin out and found a link to a website that shows the power pin out so i tested PIN #4 which i got a reading of 12V and according to the apple service manual this LED light is supposed to stay ON all the time as long as the power cable is plugged in.

So what could be the issue? Im getting 12V but the LED light is still OFF and only comes on for 1/2 of a second. Is it possible the power is bad if so why do i still get a 12V reading? Or is the logic board bad?

Anybody have any tips what else I can test to determine exactly what the issue is?

Thank you

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Replace the power supply, it has failed. Here's how:

iMac Intel 21.5" EMC 2389 Power Supply Replacement

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If the power supply is bad why would pin #4 still give me a steady 12V reading?

Isnt it possible the power supply is good but the logic board has a short/issue which is why LED #1 doesn't stay ON?

Thank you for your help


blmikek no. LED #1 is only an indicator for the check on the power supply. No other part of the system use LED 1 as indicator.

LED #1

Indicates that the trickle voltage from the power supply has been detected by the main • logic board. This LED will remain ON whenever the iMac is connected to a working AC power source. The LED will remain on even when the computer has been shut down or put to sleep. The LED will turn off only if the AC power source is disconnected or the power supply is faulty.


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