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

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Strange power on issue, blinking LED #4

iMac powers on irregularly when pressing power button.

With iMac powered off, Led #4 blinks. If I press the power button when Led #4 is in the off state, nothing happens. If I press the power button when Led #4 is in the on state, the machine will power up, and operate properly.

I have changed the power supply and power button.

Any ideas why this may occur?

Answer this question I have this problem too

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LED #4 is indicating the LCD is connected and working properly. Check both ends of the LCD connection. Check the pins and cable for damage. If the cable looks fine, disconnect the LCD and try with an external display. See if the machine powers on with it disconnected.

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The LCD connections look good. I tested with an external display and have the same results.

LED#4 is still flashing.

The machine can be powered on, but only when I press the power button when LED#4 is in the on position. If LED#4 is off when I press the power button, the machine will not power on.

If LED#4 is in the off position and I hold down the power button, it will no longer flash and it remains off.

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Im having the same issue ive ordered a new power supply, backlight board and internal power cable ill let you know if any of them work

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Chris D will be eternally grateful.
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