Q: New iMac 27inch screen flickering/tearing/shutoff

We don't know whether it is hardware or software or both, or what cures it, and though I was told otherwise in a telephone call to apple support today*, I'm not sure apple knows either. If it did, it would be doing a lot more checking on machines shipped, especially those second or third machines sent out as replacements.

Hey, we're all just speculating, right?



+* I was told a "new" firmware release would be out later this week.+

Utsava wrote:
What is strange about this problem is that is has been reported across a range of different video cards (ATI Radeon HD 4850 and 4670) and screen sizes (21.5" and 27"). This could potentially support the theory that the problem is related to something they all have in common (and not the actual GPU and/or panel).

Here's another factor nobody seems to be considering:
http://discussions.apple.com/thread.jspa?messageID=10798610#10798610

Yes, that's right, the problem is also occurring on the 24'' LED cinema display!

Dino1956 wrote:
If it were a Software Issue. That would be a blessing. Unfortunately, I think most of us do not believe that is the case. More likely to be a board or cable. The "Yellow Tinge" that I have, is just the Screen itself, I would think.

I know, I was being optimistic!
But I also wrote "But it could also some other board or cable that is common to all models"
At least, it narrows it down to some common piece of hardware.

Only time will tell!
Tic toc, tic toc... Hey Apple! hurry up will you!

DeeJay SchmeeJay wrote:

Utsava wrote:
What is strange about this problem is that is has been reported across a range of different video cards (ATI Radeon HD 4850 and 4670) and screen sizes (21.5" and 27"). This could potentially support the theory that the problem is related to something they all have in common (and not the actual GPU and/or panel).

Here's another factor nobody seems to be considering:
http://discussions.apple.com/thread.jspa?messageID=10798610#10798610

Yes, that's right, the problem is also occurring on the 24'' LED cinema display!

As far as I know all three panels have something common. They are LG.

I would again ask;
Has anyone experienced any of these Flicker/Blackout/Yellowing anomallies..... on a virgin Machine ???? (one with nothing added to the ex-factory software/hardware)

hkrause wrote:
+* I was told a "new" firmware release would be out later this week.+

Has anyone else heard of this upcoming firmware update?

Richard Prescott wrote:
And there is where you are wrong.
iStat Pro reads the fans, does not limit things to a slider. While not the same, my Mac Pro has fan speeds (4 fans being read) in the 568-700 rpm range, ambient temp is 67 F, CPUs at 74, drives in 80s. Computer is generally idle for these readings, tho access is from back to my Mac. I have seen fan readings under 1200 rpm routinely when using iStat Pro. Fan Control is just that, something to actually control the fan speed to push more air. Ask them why their slider is bottomed at 1200 rpm.
Had a customer do the iStat cause he thought temperature was the problem, but it isn't. Fact to know, if temp gets too hot and is not cooled off the computers are firmware programmed to shut down. This cut off temp is around 185 F.
The power supply is about 12 inches from the heat sink for the video card, and about 8 inches from the video card where it connects to the logic board. The pattern is a large V with the power supply at one arm end and the video heat sink at the other and the video card at the bottom of the V.

I have no idea what you're saying I'm wrong about, but I run both iStat Pro and the Fan Control preference pane. I understand how both of them work, and I'm not going to drag the thread off-topic any longer talking about fan stuff.

I have tried re-installing system software from scratch, and installing only the plainest of applications I need for my work (i.e. a text editor and an FTP program), importing nothing from my previous settings -- and I still have seen the flicker. On three different 27" iMacs. I did this just as a sanity check; no software could cause a hardware problem like this.

I agree that, because the vast majority don't have this issue, but a small minority have it across multiple machines, it certainly seems like there must be some outside factor that makes it more likely that this fault appears. I'm not an engineer, so I can only guess wildly, but the one common thread I have seen is that it is more likely to appear about 45 minutes after a cold start up, so I'm thinking temperature too. Could starting from a colder temperature (say, below 60°F) make a difference? It's winter where I am; are people in warmer climates seeing the problem?

I've also wondered about RF interference, but I am not prepared to don a tinfoil hat. Yet.

Yes..........it happens on a virgin machine.

I intentionally ran my replacement week 51 iMac on it's originally installed software before installing, or migrating any software.

The unit shipped without the firmware update.

The flickering began within about fifteen minutes. Ran the firmware update, zapped PRAM and the problem disappeared for several hours before reappearing, however it was less frequent, and less intense than before.

Wiped the HD, Clean install, and after a few hours it returned again.

Cloned old hard drive to internal, and the flickering was unchanged.

A software issue would most likely affect all, or nearly all units, not just a small portion of them, unless there was a hardware element involved.

At the risk of going off topic......

There is an issue with Fan Control, and Snow Leopard that will prevent fan speed from reverting back to system defaults, even if the app is deleted.

Here is one brief description of the issue.

http://reviews.cnet.com/8301-13727_7-10327540-263.html?tag=mfiredir

Although heating has not been completely ruled out as a cause of this issue, it is probably best to just run iStat if you are concerned about temperature. It monitors without changing system defaults.

My apologies Schwa72, that post was meant as a reply to Richard Prescott who commented on the use of Fan Control.

Did not intend to rehash old stuff.

I just got off of the phone with Apple Corporate Customer Care....again.

I contacted them a day or two before New Years, and explained that my replacement i7, week 51 is also flickering like my week 47. I explained to them that I was in no rush to exchange this unit since it was absolutely perfect, except for the occasional flickering, and even rarer screen split and blackout.

They promised to call me back on the 4th, and make arrangements for a solution.

They called as promised, but were reluctant to wait to make the replacement, and stated that they felt the issue would not appear in the new machine.

They sounded very confident, but did understand my reluctance, and agreed to wait two weeks before making the replacement. They will call back on the 18th to arrange the swap.

Never mind -- accidentally replied to a post that wasn't even intended for me!

Message was edited by: Schwa72

I returned my imac 27 only after 3 days!
It flickered even after the firmware update. It also had the yellow spots.
I saw no reason to keep a defective computer. After the 14days its YOUR comp. So they will just fix it-not replace.
I still want it again- but will not buy for months until I hear thattherte are no issues and a new graphic card is installed. AMD or ATI cards I feel are the cause.

The cause is not the ATI card. I think the Firmware update Proved that. I have the 21.5 Screen & the NVidia Graphics & I have Yellow Screen & Screen Flicker. So no we can't blame the ATI. Unless of course both the ATI & the NVidia are screwed up, which is not likely.