Chosen Solution
Hi, iMac Mid-2011. The iMac starts up but the screen remains black. The iMac works fine when using a connected Monitor. (Graphics Card OK). I have replaced the Internal Video Cable but still no screen. I have replaced the Backlight Board but still no screen (no faint screen when I shine a bright light). I was lucky enough to have another identical iMac and swapped the LCD panels over (including Video Cable) and the problem iMac still didn’t work (and its LCD worked fine on the other iMac). I fitted a replacement logic board and still the same. LEDs 1,2 & 3 come on but not 4. I have inspected all cables and can’t see any damage. Can anyone think of anything else to try? or experienced this before? Could it still be a graphics card problem even though an external monitor works fine? thanks in advance! Simon
The same GPU output drives both the internal and external displays so if the external is working we know the GPU card is good. Are you sure you don’t see the faint image of the desktop and its icons. You often need to hold the flashlight against the screen as a sharp angle not directly into the display. IF you are sure then you have a bad LVDS cable or the connector on the logic board is damaged (a common issue in this series when you yank on the cable or don’t insert it in correctly). Sometimes people put the cable in backwards which can damage some of the logic board components.
