New iMac 27inch screen flickering/tearing/shutoff

Hello all,

I have also observed this exact problem in my 27" iMac. The first time it occurred was after running in Windows for a bit--the computer had gotten quite hot so I thought it may be a thermal issue. I noticed it almost immediately after rebooting into OS X at the gray Apple logo screen. I'm not exactly sure to what extent the EFI utilizes software/drivers for video support but if I had to guess I would assume this is a hardware issue, not OS or software-related specifically because it happens during bootup. I could be wrong, though. It eventually corrected itself after the computer had been sleeping, supporting my suspicion about temperature.

Despite my hypothesis, I am having trouble reliably reproducing it and, in fact, I have had it occur after the computer was powered off for 16 hours. My current thought is either it is not heat-related or it is related to abnormal operating temps, high or low. Maybe my iMac was too cold? Again, it corrected itself after I let it sleep at some point.

Unfortunately I have not placed a call into tier 1 support for this issue because it is so sporadic I haven't observed it during their business hours. Even if I do call they will certainly step me through the normal troubleshooting fix-alls and I am unlikely to observe the problem anyway. They'll be unable to confirm or repair and I'll be frustrated having spent 30 minutes rebooting, resetting, unplugging for them to tell me to call back when it happens.

On top of the video issue, it seems like the computer does not sleep properly unless I manually put it to sleep via the OS or keyboard keys. I can hear the hard drive spinning up and down intermittently all night if I don't manually put it to sleep.

Anyone else feeling a little disappointed? Even with these problems I can't help but love this beautiful machine...I just want it to work properly!

Same thing is happening to me. Really annoying. Been happening almost since day 1. Or maybe since day 1. There was a similar issue with my MacBook Pro, but there were two settings for the display—when you switched to the low power mode (I think) it cured it. I don't think there are similar setting changes that can be made to the iMac.

My first 27" iMac went and died on me after about a week. The replacement has developed this screen flicker problem, including the flashes, the momentary black-screen and failure of "vertical hold" with the screen shifting down. (although not since I got it back out of the packaging to deauthorize my iTunes account on it!)

Apple support acknowledged straight away this is a known problem and offered a refund. Good for them - and I'll certainly be buying a 27" just as soon as Apple confirm the problem has been identified and fixed. Lovely machine - but not what I expect from Apple quality control.

Just an update from my previous post as my problem started 5 days ago and only happened a few times. I did work with a senior tech from apple on monday who had me rum hardware and s/w test's that all checked out good. He also reset my PROM.He wants me to let him know when or if it occurs again. I downloaded 10.6.2 yesterday and my machine has been running fine.
I'm keeping my fingers crossed.

I was 10.6.2 when this started, so I can't see that fixing the problem. Ironically, I've got the returning iMac out of its packaging (I'd forgotten to de-authorize the iTunes account) and there doesn't seem to be a problem now. But judging by others' experiences on here and at other forums (plus the support guy basically offering the refund immediately) I'd say it'll be back soon, perhaps when the machine has heated up enough again. Bottom line? With this and some of the other problems people are reporting, I'll wait a month or two before re-purchasing (which I will - it's a lovely machine when it works...)

Has this problem only occurred on machines with the HD 4670 GPU so far? Now that machines with the HD 4850 (a time-tested part, FWIW) are starting to hit the streets, it'll be interesting to see whether they also have the flickering problem.

Hi guys, there is something what I can not understand. How it comes that weeks after first person notice problem with an iMac and people are still reporting this issue on daily basis there is no official announcement from Apple itself.
Another thing is there anybody, or do you know anybody whose iMac is running without those problems? Does it make a sense to replace it and get a new one?
Why when calling Apple Care Support they pretend like I am the only one with this issue? It starts to be ridicules. In the end of the day all of us paid a lot off money for crap iMac (I have never expected to say anything like that about apple product).

This is my 5 day experience.

Noticed heaving flickering and slowdowns since day 1.

1. Turned off Airport
2. Reset PRAM (Hold down Command, Apple, P, R)

This fixed both flickering and slowdown for 1 weekend.

3. Installed 10.6.2 on Monday.

Slowdown is non-existent, however, flickering occurred the next day.

4. Reset PRAM again. Flickering did not return for the night.

Will check again tonight when I get home. If the flickering goes away if you reset PRAM everyday, then it appears to be a software issue. Also, noticed that my fan didn't turn on automatically on day 1. This lead to a very very hot monitor and constant flickering. After resetting the PRAM, I noticed that the fan would turn on. This helped alot. However...I'm no technician. I don't know if resetting the PRAM has anything to with the fans.

I bought mine on October 26th so I'm out of my 14 day and it's just started today. It seems to happen to me when copying via Firewire. My screen doesn't black out, I just get a couple of 1 pixel'ish lines (multi coloured) appear across the middle of the screen for a split second. I've been using the machine for less than 5 minutes before it happens.

As a side comment, I've also noticed the power switch on the back of mine is little suspect because it seems to have no movement in it at all when I go to switch it on sometimes and then on closer inspection it's not quite perfectly aligned as if it's turned slightly in it's place. This caused me a problem at the weekend when the iMac just wouldn't come on and when I noticed the fault and turned the power switch, it came on but with fans at full speed. Required all the usual resets to fix and this is the first time I've switched it on since so I don't know it it's linked.

Give me my Mac Pro any day, very worried about the iMac and never had any luck with them in the past either. Good luck everyone.

Add another to the long list.

I purchased my 27" iMac from the 14th street store in Manhattan on the 7th of November. Once I got home and booted up for the first time, I had already begun experiencing the flicker problems. To say the least, it wasn't boding well for my new machine. As everyone else here has executed, I rebooted and the problem was fixed. Until it started flickering once again on the 10th, while the AirPort kept cutting out.

Since then, I erased the OSX and Apps that came preinstalled and reinstalled everything from the disc. I also updated to 10.6.2. I haven't taken the step that Mactoubib mentioned, since I'm not too familiar playing the root folders. If the flickering starts again that may be the next move. But, so far things seem to work.

I'll keep you updated...

What would you suggest. Does it make a sense to bring back my iMac and replace it with new one? Have you heard anyone has one without those issues?

The same is happening to me. Same problem.
In Apple Support I've been told to unplug the computer, press power button for 15 seconds and then plug it again. Of course, it's better to upgrade to 10.6.2 before doing this.

AggggggHHH!!!!! It's so nice.....

yes it does help .....but for few hours. ... ;( oki doki time to pack my baby back to shop

Hi there,

To bring back or to do not bring back, this is the question. As a Mac specialist, I installed 7 of these iMacs. They all had the flickering problem, after replacing the faulty xtensions, things are back to normal, and 10.6.2 fixed the issue at least for these 7 iMac I worked on. Now is this a hardware or xtension problem, I can't tell at this point. Lot of people complaining, and I can't confirm that is hardware problem. But keep in mind, that you have one year guarantee.

Hi,

The 10.6.2 update installed new ATI drivers, but the ones in the ZIP archive you gave the link for seem to be even more recent than Apple's.

Can you tell us if they are just the same or if they are, indeed, different.

The reason why I am asking is simple : I had the flickering/etc. issue even after the update. If "your" drivers are just the same as Apple's, then I know it will come back anytime.

Thanks for confirming.