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Random Black screen, Help please

I just got a iMac 20" 2.1GHz (2006) at first it ran well no problems, but now the screen randomly goes black, system still runs just black screen, if left alone it will go to sleep and can be awaken just fine as if nothing happened but later its black again. any advise would be Appreciated

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Thanks for the replies,

I tried them all but the problem persists. I found a few other sites where others have the same issue, I’m finding a common theme the hardware seems to be ok but it looks like the drivers from apple for this specific ATI video card, in one thread they found that removing the divers help solve the problem but limited the video abilities of the system (not good).

By following your advice I did notice that when the screen comes on it’s really bright (during boot and wake from sleep) and then it dims to normal settings, that’s when the blackout happens, if it goes to normal setting it runs fine, otherwise it will black out right at the time it goes to normal settings. So I’m wondering if it’s hardware and a new mother board is needed.

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Well I think I solved the issue, tell me if I’m on the right track.

I followed every thread on this site dealing with screen issues, and learned about a thing called an Inverter, it controls the backlight for this type of screen, I also found a couple of simple tests to diagnose problem.

1. Connect a second monitor if it stays on when the onboard screen goes out, it’s not the video card.

2. When the screen goes out hold a flashlight up to the screen on a slight angle and look real hard, if you can see the desktop (in the dark) then it’s your screens backlight.

I performed these tests, secondary monitor worked when primary went out, and the flashlight test fail the first time because I was looking at a blank background so I opened some windows and there they were.

I found and ordered the part, I have the removal/installation guide, and I have the tools, as soon as the part arrives I’m going in, wish me luck.

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I recently suffered from an imac screen that went black and the system would not respond correctly in safe mode. my girlfriend was able to override the problem by typing in her password whle on the black screen and pressing enter.

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Thanks for the tip Luke. In my case the issue was also solved by simply entering the password on the black screen and then pressing enter.

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The problem with flickering screens in older iMac's isn't a problem but a safety feature. After upgrading the new features are draining the processor making the mac overheat. After disabling dashboard my processor clock dropped 20% = cooling down my mac. https://www.howtogeek.com/tips/how-to-di...

You can check out your own energy-consuming applications that run and that you don't use with this app: https://itunes.apple.com/us/app/miniusag...

I also installed a new HD that doesn't have a heat sensor build in so that means the cooling fans on the HDD and processor aren't automatic anymore. I keep the temperature of my mac under control manually (I try to keep it at 35-37°) with: https://www.macupdate.com/app/mac/47386/...

The upgrades Apple offers aren't for everyone: the bigger the update the bigger the computer you need to run it. If you have an old system, they run harder so they run hotter and start flickering screens to cool down.

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Deck the Halls
With tools and Fix Kits

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She lives,, I replaced the inverter and the power supply, not that hard of a job (I've done worst). I picked up the parts on a famous auction site both for well under $100 and with the Guides found on ifixit i brought new life to this Imac, after replacing the parts the screen seams brighter and stronger. I got this mac for the wife and now I think she'll love me long time (LOL).

Thanks ifixit, your my heroes,

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what auction site? I have the same thing going on... But I would add that lowering the brightness allowed the screen to stay on...

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Hi Gerald, my advice is try replacing the keyboard.

I had this problem and have spent weeks trying to fix it, using every suggested fix on every forum I could find. I did endless PRAM and SMC resets, installed smc fancontrol, uninstalled and reinstalled Yosemite. Every fix failed. In fact it just got worse.

My 2008 imac had become virtually unusable. As soon as it powered up the screen went black, and it sometimes got stuck in a loop of trying to restart and would only stop if I unplugged the machine from the wall.

Then I read that someone had fixed this by replacing the keyboard. I had nothing left to try, so tried it.

It worked. Everything is back to normal. No screen glitches at all. It's like a miracle cure.

I hope it works for you too :)

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Was your keyboard wireless ?

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Woo hoo! I ended up buying a new iMac a couple of years ago because I couldn't fix it. Tried a new keyboard today on the old one (Apple had also replaced the backlight board) and now the kids have their own for homework. Thank you!!

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have you tried resetting PRAM?:

Shut down the computer.

Turn on the computer.

Press and hold the Command-Option-P-R keys. You must press this key combination before the gray screen appears.

Hold the keys down until the computer restarts and you hear the startup sound for the second time (I usually let it do this till it chimes 3 times).

Release the keys.

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In the left top corner of the screen is a flat wire . Make sure it is properly seated.

It can come lose when the hard drive is replaced, and maybe you did not properly seat it back. The mac starts up, but as soon as the kernel loads it dims the screen, and then turns the screen off.

Interestingly, when I try to reboot the mac by holding the power button pressed, it would flash the screen. Apparently the power button briefly over ride the kernel control of the screen.

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hold Shift + D simultaneously while holding the power key (to turn on the mac) for 10 or 15 seconds. Seems to work anytime it's necessary, which for me has been only after system updates in el capitan.

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Thanks Dawn, worked.

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I had the black screen appear after installing office for mac - reinstalling OSX fixed the problem.

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I reinstalled OSX and iMac works fine now. Simples.

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Double check your System Pref > Desktop & Screen Saver settings.

Try changing the screen saver to something else and also check your Hot Corner settings. You could also have "Put Display Asleep" set for a corner.

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I have the issue with 'Black Screen' on my late 2010 27-inch iMac. Boots up fine, but then randomly goes black. The iMac is still alive as I can still hear things playing. Someone suggested I try putting the iMac to sleep using the cmd/alt/eject key commends. Well I tried this, and after doing the key commends then touching any key afterwards the iMac came back. Screen came back on. It did however go off again after a couple of minutes, but used the same tactics again and it worked again. Still a pain, but a solution.

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I had the same problem and the fix was easy. Download and install the SMC fan control program and bump up the speed on the HD fan. In my case the HD was too hot. I haven't had the issue since.

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Not a good solution! Best to fix the real issue Vs masking it with this App.

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I was having this issue and followed the suggestions of the OP - and it worked! I spent under $150 for parts and tools, and ended up successfully replacing the inverter board and power supply. It looked to me as they had been corrupted by moisture and dust.

Happily living life at full brightness with no problems! I will say I nearly had a heart attack taking off the screen - some of the connectors are very delicate. The power supply I bought also happened to look completely different than the one in unit - but it's working so far! (I had a "well, F**** it" moment when I saw how aesthetically different they were.)

Thanks! If anyone is curious about the repair lemme know and I can add the links I used for buying tools/fixing.

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can you help me with the link please

the wife is killing me to get it fixed

My mac is no longer usable

Thanks

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I've been dealing with this random problem for about 9 months. Could you kindly send me the solution link? Thanks, Jim

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I recently ran into the same problem with my iMac (27-inch, Mid 2010) 2.8 GHz Intel Core i5 ATI Radeon HD 5750 1024 MB computer w/ 16 GB of ram. The screen started flickering than blacking out all together shortly after updating from El Capitan to Sierra. I tried Resetting Vram, Pram, using a different keyboard, booting in safe mode, etc. Nothing worked. In the end resetting the computer back to El Capitan was the solution. No issues experienced since reverting! They do not offer hardware support for this iMac any longer, so I was glad to get back to having a monitor that functioned normally.

A couple of years ago I had the power supply replaced, but have had few other issues with it since. Hope to get a few more years out of this computer, as it is more than powerful enough for the work I do here at the office. Best of luck to those experiencing the same issue.

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Gerald Thomas will be eternally grateful.
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