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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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iMac Black Screen, No Chime. 1 LED.

Hi there,

The graphics card in our iMac Mid 2011 model packed in. Upon replacing the card, the Mac now has a black screen and does not chime.

On the logic board, only one LED comes on. If the computer is turned on, this led remains on then after roughly 10 seconds, the fans increase to their maximum speed.

I’ve tried testing the pin voltages.

Pin 3 has zero volts when I assume it should be 5V to power the Hard Drive?

Could anyone advise me on what steps to take? I’m stumped at this point.

Answer this question I have this problem too

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Are you sure the issue was the GPU board to start with. This sounds more like a bad power supply.

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@danj Yes. Originally, The Mac was stuck in a boot loop with Vertical Green bars across the Boot Screen.

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You really need the schematics to trace out the power lines on the power supply and logic board.

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2 Comments:

When I plug in a wired keyboard too, it does not receive any power.

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You likely need a new power supply then

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Thomas Govern will be eternally grateful.
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