Model A1311 / Mid 2011 / 2.5 & 2.7 GHz Core i5 or 2.8 GHz Core i7 Processor

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Sometimes screen goes black upon startup, looks like going in sleep mode

Hi there,

The problem:

Sometimes upon startup the screen lights up normally, but after one or two seconds the screen goes totally black, but the iMac still starts ok. I can hear the bong sound and the hard drive working.

Sometimes just before the screen goes black, it very slightly blinks, then goes black.

The workaround:

Wait that start up process is finished, then press the power button once, wait 10 seconds, and press it again, as to put it to sleep mode and back. Then the iMac works perfectly.

I suspect the power button, as it doesn't have a frank feeling when pressed, it feels a bit sticky, as compared to other iMac.

So I was wondering if there is a way to replace the power button ?

Many thanks,

Regards from Montpellier (France).

Cyril.

Answered! View the answer I have this problem too

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Chosen Solution

Apple uses a soft power button approach. Basically the power button is a low voltage momentary on and within the power supply the signal is used to control the power supply.

From your description I suspect the real issue is the power supply not the button. In any case you will need to remove it to even get to the button.

  • Power supply, 204W 661-5299

No P/N for the button as its part of the read housing. You'll need to find a junker or someone who has one to strip the part from.

But before you do that... Use a flashlight to shine at the display at an angle do you see your desktop (it will be faint) after you first start it up? If you do then the real problem is a bad backlight unit which is the first thing I would check.

  • LED Backlight board 661-5976

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Comments:

Thanks Dan, I will do the flashlight test prior to think about replacing the power supply or finding the button from a broken iMac.

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Cyril Eybert will be eternally grateful.
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