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iMac Intel 27" EMC 2309 (Late 2009, Core 2 Duo 3.06 or 3.33 GHz) ID iMac10,1, EMC 2374 (Late 2009, Core i5 2.66 GHz or Core i7 2.8 GHz) ID iMac11,1

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iMac 27" Black Screen

iMac 27" 2009 i7 2.8GHz

I bought this machine and the V-Sync cable was damaged and during transit from the seller it stopped working due to the munched up 4 contact pads on the flex connector. I temporarily fixed it by using crazy glue under the tracks and pushing the contacts back down onto the plastic strip. Cleaned off the contacts and got the display back. However, I had to take it apart again and next time I reassembled it would not work. I received a replacement V-Sync cable from the seller and tested it with a multimeter. Contacts all in good shape (under my microscope). Replaced it but I still have a black screen.

Have reset SMC and PRAM, tried Command F2 to make sure I was not in display mode. Shining flashlight on screen it does not have an image so I do not think this is just a backlight issue. I also tried an external display and it also does not show an image.

If the backlight board was blown I am assuming it would not affect external display but when I had the bad cable initially it also would not display external. Can someone confirm if a bad backlight board could cause these symptoms? What is the most likely culprit? Maybe the 4850 graphics card? Could the Display Panel itself be damaged from this cable being defective? But that wouldn't explain no external display...

Open to ideas....

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Thanks for the quick reply.

The video card seems very securely fastened in place by the metal bracket that attaches to the logic board and holds the heatsink in place. It would surprise me if it could move enough to affect the connector. Also, what confuses me is that when I first received it the V-sync cable repair fixed the issue so it makes me suspect that circuit. Any bumps or shocks on video card should have already done their damage in moving the card. With the V-Sync cable not making correct contact the symptoms were the same. No external display.

What does the V-Sync actually do? I would have thought that the LVDS connector should carry all necessary signals to the panel. Unless the V-Sync is responsible for "syncing" the backlight to the display refresh (if that even makes sense). As far as I know the LED's are just fed a DC voltage so there should not be any flicker to compensate.


is your late 2009 27 "iMac working good now? I had a white screen w/2 second beeps. Ended up being the HD. So I r&r'd it with a new HD. But now it is black screen. I have ordered a new vsync ribbon as mine is trashed. Was you video/graphics card loose? Where is it located? I don't really want to landfill this rig.....


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You might check to see if the video/graphics card in the iMac is not fully seated. This would cause no display on the internal and external displays. I do not think that the display panel would be damaged but the glue might have done something that affected the panel in some way which seems very unlikely. I would see if the video card is loose. I once got dust between the graphics card and the slot and it caused it to have graphical errors. You might also want to clean the graphics card contacts and slot with compressed air.

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dadioh sarà eternamente grato.
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