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

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Dead Display, system starts fine


Display went to black.

But starts fine. Machine is reacting on change of speaker volume.

Starts perfectly in terminal mode (but black).

Alt-cmd-R.P reset doesn't work out.

External Monitor attached : nope.

Running iMac as an external Monitor on a macbook: negative (maybe wrong cable, or the function for F1, F2 is disabled in sytem prefs.).

What couldit be:

Display or GPU?

Usually, if a graphic card is saying good-bye, you see some errors on the screen before. But this time not. Just turned black some day when booting.

I've removed the display , yet. Is there a diagnostic method of testing, weather display or graphic card is the problem? Or Backlight?

Many thanks,


Answered! View the answer I have this problem too

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FYI: The iMac won't run as an external monitor from your MacBook. The iMac's display port connection is output only.


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Try this see if you can access your iMac from the MacBook over an Ethernet connection. Click on the menu Go then Network do you see your iMac system? If you do try sharing the display option at that point you'er accessing the system virtually over the network.

  • If you can that implies your GPU card is gone as you stated you can't access an external display either. You'll need a new GPU card. Follow this IFIXIT guide: iMac Intel 21.5" EMC 2428 GPU Card Replacement
  • If you can't see or access the your iMac over the network and you are sure you have a good connection with the cable then the Platform Controller Hub has failed which will require a new main logic board. Follow this IFIXIT guide: iMac Intel 21.5" EMC 2428 Logic Board Replacement
iMac Intel 21.5" EMC 2428 Logic Board Image


iMac Intel 21.5" EMC 2428 Logic Board Replacement



1 - 4 hours

iMac Intel 21.5" EMC 2428 GPU Card Image


iMac Intel 21.5" EMC 2428 GPU Card Replacement



3 - 4 hours

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To prove if the backlight had gone you would use a flashlight held against the display at an angle to see if you could see a faint outline of your desktop icons. But as you stated an external display did not work (HDMI or VGA) that in my mind aimed me to the GPU or the logic board.

I agree I often see odd screen artifacts just before the full failure of the GPU which is why you need to be sure here the logic board didn't go.


Many thanks for all your comments and ideas.

I made all checks, also via ethernet.

Result: GPU is gone.


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Try to plug another monitor to check the graphic card.

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pferdeschloss will be eternally grateful.
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