LED 2 lights won't stay on at 2011 iMac 27", what could be wrong?

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Level 1

14 points

LED 2 lights won't stay on at 2011 iMac 27", what could be wrong?

Recently add SSD installed on my iMac and did dust cleaning, however, after putting everything back, it won’t start, remove the display panel and found the followings:

Connect the power cable, LED 1 lights up.
Press power button, LED 2 lights up very shortly, then lights off quickly, 2 seconds later, LED2 lights up again, but off quickly, it then goes into this loop.
I can see fans are spinning for a short of time when LED 2 lights up, but stop spinning when LED2 goes off.

I double checked everything, can’t see any cable connected wrongly.

Does anyone know what could be wrong here?

Many thanks,

Posted on Feb 1, 2022 10:44 AM

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Answer 1

Top-ranking reply

HWTech

Level 9

68,708 points

Mar 4, 2022 12:37 PM in response to lovecd

The second LED should remain lit for as long as the Mac is powered on and not asleep. A problem here indicates a power supply issue or voltage regulator issue. Perhaps a cable from the power supply to Logic Board is disconnected or not fully seated. Make sure the iMac is unplugged, then press & hold the power button to help drain power from the iMac. It is best to wait at least several hours before working inside the iMac especially around the power supply since the power supply can retain a very nasty & dangerous charge for hours.

As for what may have happened....who knows. Maybe you accidentally did something during the upgrade or perhaps the failure is coincidental especially since the iMac is over 10 years old. Double-check all the cables are connected and fully seated. Make sure the power button cable is connected and is not damaged. Make sure the power button is functioning correctly. Next after that would be a power supply followed by the Logic Board.

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