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

Ettore dn wrote:
2. replace the part in all new units, find a software/firmware workaround ("update") and let all users download it => cost near $0.

Think from a Apple (or any company) perspective. What would you do?

Exactly right, Ettore dn; Apple will probably do whatever is most cost-effective. Sadly, the upcoming update in a few weeks may possibly turn out to be just another placebo. I truly hope that I am wrong.

Warren, I was referring to this!


Update: Just got a phone call from Apple. Basically he looked at my Pictures I had sent via email & confirmed there was indeed a Color Variance on my Screen. He basically & very honestly told me this is just a follow up phone call to get more info from me. He then told me Apple does not currently have a fix. They are working on it. He also said, the they were told they may have a fix in 3 weeks. He also said it could take longer. When I asked why Apple never tried a firmware fix for the 21" iMac. He said, at the time we did not know the 21" had a problem. But we do now. I told him I just don't want to keep swapping out iMacs, only to get another faulty one. He completely understood & agreed. He said he or someone else will get back to me when there is a definite fix. He was polite, professional & empathetic to my situation. Bottom line is he was honest. They don't have a fix yet! So I will wait patiently. I feel better now. I also made a joke & said, if it's not fixed for 6 Months, will they upgrade me to the future Model iMac. He laughed & said, No, it will be resolved by then.

Ettore dn wrote:
Now i spent some time to do some research on google. Check out this:

http://en.wikipedia.org/wiki/Triplebuffering#Double_buffering_in_computergraphics
http://en.wikipedia.org/wiki/Vertical_synchronization

Hello again Ettore dn,

Thanks for the links. While some of the information was a little above my level of understanding, I did read them both in their entirety, and found them both interesting and informative.

I also read these two pages:

http://en.wikipedia.org/wiki/Screen_tearing

http://en.wikipedia.org/wiki/Refresh_rate

Dino1956 wrote:
Warren, *Read my update above. I talked to Apple.*

It's really hard to notice Color Variance in Applications or White Screen. But as soon as I put up the Grey Bars, I see it!

Hello Dino,

Thanks for sharing your phone call with us. Very interesting. It has provided me with some guidance regarding how to proceed with my own defective iMac. I was planning to contact my AAR tomorrow regarding the yellow tinge, which, it seems may be a little worse than yours, since it is definitely noticeable on pages with white backgrounds -- such as this forum -- while on your machine it apparently is not.

I believe that I now have sufficient evidence to make a case with my AAR. However, as this thread has made clear, until this "fix" comes out in a few weeks, it would seem that we are all now in standby mode with little else to do.

Let me make a final comment here for now.

After reading those various Wikipedia pages, as well as the recent exchanges between Ettore dn and Jacques LAPORTE, based on my limited understanding, I am left with the impression that the common element between some of these problems is the size of the LCD screen . . . at least with the 27" screen. I may be totally off-base with this remark, but I am getting the sense that the current hardware/software configuration simply is not good enough, or calibrated properly, to support such a huge 27" screen, particularly a screen that is made by a company -- LG Technologies -- which some folks have criticized for its inferior products.

Any comments?

What about the 21.5" Screen? Is that too Large for Calibration as well? I've been saying it again & again. It's not just the 27" Screen & it's not just the ATI Card. Same problems on both Screens. This is not true because I know someone with a Perfect 24" iMac screen.

I also have a 24" imac, I have never had ANY problems with that machine but I have to admit it has one stuck pixel (magenta) and that is just one of the reasons I was replacing it with the 27" imac....I never did quite love it as much as I should have because of that minor flaw. If only I knew then what I know now, of just how MINOR a flaw that is! But absolutely NO colour degradation or problems with that display, other than the one stuck pixel.

BTW, my 27" imac does have over a dozen dead pixels on the isight...normally does not really bother me because I don't use it that much, but why is it so crappy? It's supposed to be an overpriced perfectly designed beautiful machine.....oh, I long for the good ol' days of apple (pre-iPad, obviously).

Dino1956 wrote:
What about the 21.5" Screen? Is that too Large for Calibration as well? I've been saying it again & again. It's not just the 27" Screen & it's not just the ATI Card. Same problems on both Screens. This is not true because I know someone with a Perfect 24" iMac screen.

Hello Dino,

No one is denying that the 21.5" iMac also has its share of problems. You have certainly made that point enough times throughout this thread . . . to the point of ad nauseam, I dare say.

However, you also need to understand that when most people post here, they post regarding their personal experiences with the machine that they happen to own. In my case, that is a 27" iMac. For me to discuss the 21" iMac would be speaking out of my league, because I am not familiar with that machine.

We also have a week 42 24" iMac in our home, and to date -- after four months -- it continues to operate without any problems . . . which is exactly why I am personally perplexed regarding the problems with the current line of iMacs.

Ettore,
It is in my case a very intermittent issue difficult to study. But I was lucky this morning in december my video cam was ready. The sound I heard and recorded is not associated to the 'flickering' artefacts (usually 3) but with the display blackout the always follows.
It's the kind of noise you can hear when you put the computer to sleep. I suggest a relay but maybe i'm wrong.
I thinking of a chain scenario like this:
- an event (RF interferences maybe or whatever - but not thermal) is triggering a profile switching (to adjust performance at off-peak) ; some values are drifted and the result is what we see and call 'flickering',
- after a series of flicks, the graphic sub system is shutting off trying to protect itself.

When we put the display to sleep, the wake action resets values (refresh rates ... or whatever) to default.

What triggers the chain might be hardware (sync cable unseated ; but why do they change the panel) or software (for example firmware overreaction to a change of profile) ; could be also a mix.

But what I see on my screen (and I've seen a lot of machines in my life) is the result of conflicting signals in the system - a graphic panic.

Keep on the good work and stay focused on topic.
Jacques.

Hi Warren,

Apple has the all means to diagnose and correct this. It's very intermittent, that's possibly why it takes time. Put probes on selected test points, wait and record signals : one of these days you'll catch it.
Maybe it's already done.

I just hope so.

Warren, (this time) the reason I mentioned the 21" is because you were saying maybe the screen is too large to have a perfect calibration. I was merely stating, then why would the smaller screens have the same issue. In other words, it has nothing to do with the size of the screen being too large. If that had been the case, then the issue would only effect 27" Screens. Just to Clarify what I meant.

Hi everyone just wanted to update you all and let you know that the computer is still good. No problems and a pleasure to work on. Sorry most of you are still waiting for a fix but hang in there. Best of luck,
Rick.

Dino's phone call with Apple is the best information we got in the last ten days. This information is clear and honest. Thank you Dino!

So what can we do in the meantime? "Ettore's links" are very interesting to discuss, but also very complicate to understand. The most important article seems to be "Double buffering in computer graphics". It would be very friendly if someone here on this thread could explain it a little bit. I have to say, that the article is to technical for me. Thank you Ettore for these links, great job!

It's logical that from time to time we're off topic here, because as Warren pointed out: " ... we are all now in standby mode with little else to do."

Jacques LAPORTE wrote:
So, if I can imagine they can possibly find a software fix for the flicker (after all the sleep/wake procedure is a sort of reset action), for the color variability (yellowing) I see – maybe I’m wrong- a hardware fix since it is more likely a manufacturing defect or the result of rough Handling.

See this interesting post of a guy that fixed himself his LCD panel.

http://www.iclarified.com/entry/index.php?enid=7407

Hello Again Jacques,

I read that same account on the Gizmodo site the other day.

In light of what that person states regarding a physical defect in the LCD layer being the cause of the yellow tinge problem, you seem to be saying above that no firmware fix -- now, or three weeks from now -- is going to resolve the yellow tinge issue, since it is a physical -- and NOT software -- problem. Am I correct in my assumption? In other words, in your opinion, are those of us who are experiencing the yellow tinge waiting in vain for the upcoming firmware update?

Thanks!

Hi Warren,

I've understood as you he realigned the layer that diffuses the LED backlight manually to have perfectly even colors. I just said that it seems to me difficult for a piece of firmware to do that. But looking at the specs of the ATI 4850 (see what they call 'ATI Avivo Video Post Processor'), maybe they could have a firmware workaround. Honestly, that's why I added 'maybe I'm wrong' in my post, I'm not that specialized !!

http://www.amd.com/us/products/desktop/graphics/ati-radeon-hd-4000/hd-4850/Pages /ati-radeon-hd-4850-specifications.aspx

Cheers