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iMac 27" Screen goes black repeatedly, but then...

I picked up my iMac today from Apple. They replaced the LED backlight boards. I've been using it non-stop tonight (about 6 hours straight) and have not experienced any problems. Everything on the Mac is how it was, the drive was not erased for a Lion reinstall. So far so good. If it starts acting up, I'll post another update.

We're having identical problems with identical machines. Very frustrating isn't it? The way I get my screen back on is hitting Control+shift+eject buttons all at the same time. This is the keystroke combination to switch montors from internal to external. Sometimes I feel like I'm playing a video game to keep the thing on when it starts shutting off every two seconds.

I'm resigned to making an appointment at the genius bar. What I've read points to the video card. I read a VERY involved message somewhere about a method of flashing a firmware update to the video card BUT it involved having Windows loaded in some fashion and was more time consuming than I am willing to do. But if they (Apple) swap the card, you'll end up with one with the new firmware and problem (supposedly) eliminated.

Glad I am not the only one that its having it happen so repeatedly.  Wierd thing is since posting my message this morning it has only gone off once and is running happily at the moment..... wierd!

I am not against loading Windows on via boot camp as long as its not too involved I guess, so it will be interesting if someone comes along who has more experience of that.  I think I would rather do that than have to take it in and risk losing my data.

Thanks for the keyboard shortcut to get the screen to come on too.

Thank you.

Glad I could help a little.

It's unpredictable. I had a good day on Friday and Saturday, now today it's back doing it again.

Mine has been doing this more and more for the last two weeks and finally got to the point where it runs for aobut 9 minutes and then quits!

However, it will then go on a spell where it will run for an hour and then something will start not working right, e.g., can't put something into the trash.   I'll try to make it restart and it will crash,

I have also tested it by connecting a firewire cable between the 27"iMac and my 13" MBP with the iMac turned off. Then I turn on the iMac holding down the T key which lets the Hard Drive of the iMac be accessible on the MBP as an external drive.   The iMac will show a screen saver and I can see the files on the iMac Hard drive.  But then it will quit and the connection to it's hard drive from the MBP is lost at the same time.

When the iMac quits, the screen goes black.  Nothing works, although I am waiting now for it to quit again so I can try the 3 button step mentioned above.     However, if I listen very close i can hear the fan running inside and if I press and hold the power button, then I hear a 'clunk' and the fans go off.   It will restart but is very slow in doing it.

Also, one time it quit in the morning when it was cool in my room and it had only been on for 10 minutes.  The bottom of the back of the iMac was still cool to the touch and the top of the case was only slightly warm to my cheek so I don't think this is a heat problem.

Finally, there was a long discussion that evolved into the 15" MBP and concerns about Lion.  I have Lion 10.7.4 (11E53) installed on it, my 24" iMac, my 13" MBP and on this older miniMac.   None of the other 3 have any problems and all work solid.   The 24" iMac is left powered on 24/7 for months at a time and puts itself to sleep when we are away from it but otherwise it is always on and no issues.

I had done the SMC and the PRAM resets to no avail.

I called Apple Service yesterday (6/23/12) and she had me check the HD which came back fine.   While she was trying to get thru the rest of her tests, it failed twice!   She told me to take it to a local Apple repair shop as I am >150 miles from the closest center which for me would be KCMO.

So, Steppy, you are not alone here and I will be sure to let the group know what I find.    The thing I am most concerned about it they will keep it and say they found nothing and I am not interested in working on a computer that can stop without warning!!

C U All

Jim

One More note

It just quit after playing internet radio on iTunes for about an hour.   I started copying some files over from it to an external hard drive via the firewire.   Did a 250 MB set of files and all was fine.  Started to open some other files to see if I needed to copy them over and it stopped with a black screen and this time was making a pulsing noise from the interior of the computer.  It's the first time I heard this noise   It was not the internet music still playing. 

(As a complete aside, I was playing the same station on the 13"MBP and it kept playing the music.)

I then cycled the power off and the pulsing noise went away.  I tried it restart and it took a long time to get to a screen but before anything could happen, it stopped and I had to hold the power button to get it to turn off.   I restarted it and it made the chime sound but would not restart (Attempted Twice) and the screen stayed black.

I then pulled the power plug and reinserted it.   It then came up with the white screen for about 5 seconds and then went black.

Maybe it has finally died!!   If so, they should be able to figure out what has happened to it tomorrow when I take it in.

C U all

Jim

Thanks for your reply Jim, yes its good to know I am not alone.

Like you,  I dont want to take it in only for them not to find anything. I will be very interested to hear how you get on.

Thank you.

Here's an update on mine.

I drove 50 minutes to the Genius Bar today and, of course, it would not do the montior shutting off trick while I was in the store and it had been doing it (this very morning) to the point that it was nearly impossible to use. I get to the store and nada. Go figure.

Anyways... the genius gave me a course of actions to try to narrow it down as to the cause and eliminate some possibilities.

First, try making a new user account. If it quits doing the blacking out while using the second account, then it's something tied into the first account.

IF it continues to black out after making a new account, he suggested I reinstall Lion (not wiping the drive, just over existing install and this should leave all my personal settings alone)

If that does not work, he suggested I go into the disk utilities and wipe the drive then do a fresh install of Lion. If I restore anything from a backup to only get non-App files such as docs, pics, music. Manually reinstall all my apps.

And if it STILL continues to do, bring it back into the bar and leave it with them. It could take 1 to 2 weeks to diagnose and fix.

I got home, set the Mac backup and BAM, the screen was blacking out! Why couldn't it have done that at the Apple store?

I'm trying the new user now, I'll keep you posted as to the success on it.

How frustrating for you.

I thought I had found a pattern to mine..... it seems that whenever I did a shutdown, then a restart it would black out within 3 seconds of the grey start up screen appearing.  It did that 3 times in a row, then next time it didn't

I have bought another external drive in addition to my time machine backup to have purely for a Carbon Copy Clone of my drive, just in case I have to resort to wiping and starting again.

Having come from Windows and knowing it well, I feel a bit out of my depth on this one, even to the point of doing a re-install which I have done countless times on Windows machines.

I look forward to hearing how you get on with a new user account.

Hi Steppy and others

Here is the update on my machine.   I took it to the local Mac service center on Monday morning and aafter a few days I called and they told me they had just received the new Logic board and should have it in then or the next day but given the inermittent nature ( Which they had seen fortunately!)  they wanted to burn it in.  On Thursday they called and said that was not the problem and so they were changing out the Video card.

Friday just before closing time they called and said it seemed to be working OK there but for me to pick it up and let them know if there were any problems.

I got it home and now have a different problem.   It booted right up and so I started iTunes to let it just play in the background but as soon as I started it, it started pixelating the screen.  within just about a minute I had 7 noticable bands of pixels.  Fortunately I was able to grab my camera and take a screen shot of it.  The music continued playing that song although the time progress bar in iTunes quit updating and I had lost any mouse control.   I had to power it off by the power switch.

I waited awhile and restarted it.  It seemed to work just fine and I played quite a few songs on iTunes and decided maybe that first pixilation was just a fluke.   I tried to start Parallels but found the change in the logic board had messed up my Parallels registration.   While I was looking for the password stuff, I realized the machine was hung up and un responsive to the mouse and keyboard.

I rebooted and started something else but before I got going, the machine again froze with an unresponsive mouse and keyboard so I just shut it down and got it ready to return to them on Monday

An additional note,   In every failure / hung situation, I never lost the screen as I did before  and the mouse cursor would always continue to move, just no response to clicks on it nor any responses to Keyboard inputs.

Sorry for the long story, and even more that I don't have any real news to report - other than the screen is no longer going black!  So maybe part of the issue at hand is the video card.  What else is lurking remains to be seen and I'll let you all know more as soon as they do some more troubleshooting.

C U All

Jim

That a real kick in the teeth, one problem swapped for another.

I wonder if we will ever find a definitive answer to this problem

Apple.... I hope you are watching out there, this was my 1st Apple purchase and I'm not very impressed

Hop you get it sorted.

Well after a pretty good weekend, with Sunday the screen going black just the once, it has not started to get really bad again.

When I first wake it up the screen will behave for about 30 mins, then it will play up and only stay on for about 3 secs at a time.  This carries on for about 10-15 mins, then after that it will be fine for the rest of the night, maybe going off once, but will stay on after doing the "Shift+Ctrl+Eject" trick.

I did a Carbon Copy Clone of my drive and booted from that and had exactly the same problem, so I would seem to point to a hardware issue

Well finally some good news!  The iMac seems to be working fine after they put a 2nd new video card into it.  I've been running it for a day now and no problems and the screen is extremely sharp and clear.

Recall the first time they replaced the video card it wound up with a bad case of pixelitis ( new word I just invented ) and their fix was to just get another card from Apple and replace this one.  It makes me think the video card design may be on the ragged edge or there was a issue with some of the card components.

That's all for now but I hope this has helped some of you in figuring out your issues.

CU

Jim

Thanks for the update.

Good news that you seem to have finally got your iMac sorted.  Its good to know now that if mine deteriorates any more then I have an idea on what needs to be done.

I am going to wait until Mountain Lion comes out and see if for some reason things improve, just in case its a software issue ......

I will definitely be buying the extended Apple Care before my warranty expires at the end of August.

I had a similar problem with mine as well. I've had the iMac for 8 mths. The screen started flickering and then this past tuesday, the left side of the screen went a lot darker than the right side. I called apple and after some troubleshooting (which didn't work) I had to take it in where they replaced the LCD screen.

最後更新：2017-10-17 13:58:01

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