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

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Backlight turning off, inverter-board changed

Hi, my late 2009 iMac 27" is killing me. Display goes black 10 times a day. When I hold a flashlight to the screen I can see stuff on the screen. External Monitor works fine. Regarding to some other articles on ifixit, the backlightboard should be damaged.

So i ordered one from the US (I´m in germany) and replaced the old one... same failure *crying loud*.

Do you think i should change the backlight cable also? I can only find one on the internet and thats &##* expensive (more expensive then the board itself). Where do you guys get those cables?

Does anyone know why the display is turning off in such irregular intervals? Is it a heatproblem??

Maybe i should plug out the display-thermal-sensor-cable an see if it is still turning off?!

Thank you!

Answered! View the answer I have this problem too

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Start by resetting the SMC - http://support.apple.com/kb/HT3964 See if that sets things right. Without knowing which model you have we can't answer this - Please give us the last four digits of your serial number so we can correctly identify your system.

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thx Dan, already resetted the SMC multiple times. My Serial ends with 55PJ.

Greetz Joe

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iMac "Core i5" 2.66 27"

Model No: A1312 (EMC 2374)

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Just to make sure were on the right track here. Your system has LED backlighting not CFL's. So to be clear here you replaced the display LED backlight unit 'backlighting board' as well as the LED driver board 'inverter changed' correct?

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I only changed the LED-Driver-Board by following this guide: iMac Intel 27" EMC 2309 and 2374 LED Driver Board Replacement

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Check your display settings. Turn off the Ambient Light setting. Also check your Desktop & Screen Saver settings make sure the Start Screen Saver is put to never. Restart your system and see what happens.

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so theres a second board i could change? I cant find anything on google on "backlighting board imac". Is it part ot the Display or maybe the board next to the driver board? thx

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ah .. didnt see your last comment. Screensaver is disabled. There´s no "Ambient Light" setting in the Displays preferences availible. I know the option to automatically adjust brightness from my macbook but the iMac doesnt have this feature( or the killd it in the Upgrade to MountainLion).

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Just want to make sure were not looking for snipes. Not all of the iMacs have an Ambient Light sensor so the option may not show up. Yes there is a second part here that could be the issue but I don't think it's the case here given the symptoms. The LED backlight panel which is part of the display unit. I still think something else is the cause here. The LED panel rarely fails and when it does its only an LED or two that die (depending on your system and display you have12 - 18 LED's along the edge).

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what do you think about the backlight cable? Could this be the reason for my problem? Hard to find one over here...

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No, I don't think its the cable. I'm starting to think its something on the logic board. Can you run Apple Hardware Test http://support.apple.com/kb/HT1509 to see what it tells us.

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looks like the GPU, i had similar problem - check here: http://forums.macrumors.com/showthread.p...

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Hey Don,

thx for the link. This sounds interesting. I think i lack the skill to find that "enabeling" - pin and put voltage on it without killing some other parts. My Mac works most of the time. The display isnt´t permanently black as yours. I noticed that it fails more often in shorter periods the higher the brightness setting is. I was looking for a new logic board but the prices are way to high to be economic.

Maybe ill come back to your method once the display fails permanently :)

THx Don...

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Just in case, I would recommend you keep a good backup of your data and make sure you keep it updated.

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yes, im running a TimeMachine. I did a clean install algain to see if its software related. This Problem is solo annoying. Mostly the Display fails when i got the most work to do :)

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It might be a faulty vertical sync cable, they say: iMac 27" Black Screen

It´s cheap if you find a used one.

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I did some work on my iMac 27" at home and the thin ribbon cable to the lcd board stripped off the gold, I was trying to be careful but the connector did the damage when I was unplugging it, I ordered a new ribbon cable, but the fix I found was to use some supper glue on the ribbon and then press the gold connectors quickly with out gluing it to my fingers, that worked well and I have the new one as a spare. I think Apple could use stronger connectors and still be a great machine even when folks do their own work, It hurts Apple to make it harder for folks to work on their machines. In the long run more folks would use iMacs if repairs were cheaper and easier. Most jobs are difficult because of the feeble connectors, one wrong move and they can break and turn a simple replacement job into a nightmare job in a split second. I think Apple has done this on purpose. IMO

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Joe will be eternally grateful.
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