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Modelo A1312 / Mediados de 2011 / Procesador Core i5 de 2.7 & 3.1 GHz o Core i7 de 3.4 GHz

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No Display/Video Output (Unlit 4th Diagnositic Light)

Hi all,

I was looking for some help to see anyone could point me in the right direction.

My iMac 2011, 27” currently has no display output both with the internal LCD display or through an external monitor. I've also tested a second LCD display with no luck.

The 4th diagnositic light isn't on when the display is connected, but the other 3 are. The device boots with the chime and is accessible via SSH. When the display is fully disconnected the device will boot with the fans maxed out but doesn't do this if it is connected (not sure if this helps).

I have also tested multiple video cards, I'm confident this isn't at fault either.

If anyone could help I'd be extremely grateful, cheers!

Contestado! Ver respuesta Yo también tengo este problema

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Solución Elegida

If you can get to the system remotely that’s a good sign! But it doesn’t tell us for sure where the problem is. I would plug in an external display display does your desktop show up on it?

If it does then your issue is within the display assembly. I’ve seen a few have problems within the T-CON board, replacing the assembly solved it. Here’s one source for the part 27” iMac Display Assembly, Apple P/N 661-6615

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Nothing through an external display either unfortunately!

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@addisonwtaylor - Lets try one more test. With the system fully assembled, restart your system and press the T key. This will force the system to use the intergraded graphics engine within the Intel CPU. You should see the FireWire or Thunderbolt icons on the screen if you do that tells us the MXM GPU board has died.

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@danj No luck I'm afraid, nothing displayed still after holding T and no difference after leaving the pram battery out and swapping for a replacement. So frustrating!

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@addisonwtaylor - Not good. Are you sure you were access you iMac's drive?

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I'm 90% sure I had, I'll have to probably pull the board and test it in another machine as I'm guessing there's a fault with it at this point!

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Could be a pram issue

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Why do you think that?

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I haven't attempted a PRAM reset but I will give it a shot, I'm surprised I haven't tried it actually.

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@danj I would do more on MacBooks have had about 1 iMac to deal. Seen a northridge fix video he had 3 lights with no display and it was the pram battery was the issue

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@tech_ni - This system series uses a PCH chip which holds both the North & South bridge functions into one chip.

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Addison Taylor estará eternamente agradecido.
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