iMac Intel 20" EMC 2105 and 2118

Model A1174 with 2 GHz Core Duo or Model A1207 with 2.16 or 2.33 GHz Core 2 Duo

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Screen black after boot, secondary display working

I got my hands on this core duo iMac; according to the previous owner the screen just suddenly died. He removed the RAM, so I put some new RAM in myself. I can get it to boot properly, and with an external display connected and mirrored displays, I can login and use the computer just fine.

Searching these forums I found that the issue is probably related to the GPU - is the secondary display not connected to the graphics card then? Are there any other options? Like the inverter or perhaps the display itself?

I also read that the graphics card is actually soldered on the motherboard, does that mean I'd have to replace the entire logic board, instead of just the GPU, as you would with non-mac PC's? Is there maybe some sort of diagnostic tool that can tell me what piece of hardware is failing?

Thanks for your answers.

Answered! View the answer I have this problem too

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Forget the graphics card, it's fine or the external monitor wouldn't work. Your concern is with the LCD, the inverter and the cables to them. Can you see the desktop at all? Do you get any type of light on the screen? Do you know if the previous owner or anyone else has been into it?

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The screen remains completely black, no light bleeding whatsoever, no desktop, nothing. The previous owner hasn't opened it up. So probably the LCD? According to the previous owner the screen just went *poof*

by Hans Pieter

And about the graphics card, I got confused because of this thread: http://www.ifixit.com/Answers/View/40907...

by Hans Pieter

I made an error on that thread and wrote the opposite of what I meant to say. It's been corrected.

by mayer

I figured as much after your earlier reply :) But since there's no light bleeding or shade on the display, is it likely that the converter is faulty, or perhaps the LCD? I'm going to open the unit in a couple of hours and see if there's any clue. I might as well replace both.

by Hans Pieter

If the inverter goes, you can usually see the desktop darkly. Hold a flashlight at an angle to see the screen. Check the diagnostic LEDs to the right of the ram

by mayer

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It turned out to be the inverter indeed! I ordered a spare via eBay, replaced it, and the screen is working just fine! Thanks for your help Mayer!

I have one minor issue though, in the corners of the screen, there is some color difference, there are some darker spots. I think it has to do with the shielding, as I ripped some of the aluminum tape when I took the iMac apart.

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Hans Pieter will be eternally grateful.

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