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Question: Greyish Smudge marks behind the glass screen.

I have a 21.5 iMac bought in November 2009.

There appears to be numerous greyish smudge marks behind the glass screen on the top left hand corner.

It was not apparent to me at first, but after I started using OMMWriter it became easily visible. I also tried placing a neutral white background like TextEdit and it was easily visible even then.

I have cleaned the screen on numerous occasions and it has not had any effect.

What should I do?

These spots are quite disturbing.

iMac 21.5, November 2009, Mac OS X (10.6.2)

Posted on

Question marked as Solved

Really sorry that I could not post an answer sooner.

My iMac was under extended waranty. So I just called Apple. They came to my home with a brand new LCD and refitted it.

Thanks Apple.

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Question marked as Helpful

Jul 24, 2013 1:18 PM in response to John Hall In response to John Hall

Ranjoharbi -

Your comments were already censored an hour ago. Hopefully, my comment will survive. You can contact me at justin.evans @ brytewerks.com. I will happily testify on your behalf. I've had my screen replaced FOUR TIMES. I'm a mechanical & systems engineer and work with these products every day; I know exactly what is creating the problem.

Most of the people on here have good intentions but they confuse what they observe with science; the problem is a poorly conceived air filtration system combined with high-humidity environments. Living in Florida, the tropics, summertime in the midwest or using a humidifier is the catalyst because dust particulates in the air contain enough excess moisture that they clump up behind the LCD panel and accumulate into what look like giant stains.

The solution for Apple is simple; a removable HEPA filter in the base of the iMac would filter out particulate down to 3 microns. One simply pops open the HEPA filter's cover, removes it, rinses it our or replaces it and the problem would not occur.

Instead of solving the problem Apple would rather censor this thread. It is the worst kind of incompetence. So, yes, I will gladly testify for you. Email me before this message gets deleted. You know the idiots who censor this thread will delete this very, very soon.

I've been part of this thread for nearly two years. I was one of the original people complaining about the problem (and originally thought it was a heat issue.) Each time my "screen goes bad" I've studied the problem in greater detail. Since I have AppleCare I demand they repair the system in my home and I thoroughly document the repair process. Its amazingly simple; they just remove the glass bezel, carefully remove the LCD panel and then replace both...without dusting the system or addressing the real problem. Inevitably, the dust spots return. I've wiped the dust with my fingers; it is clumpy due to moisture.

Apple loves to point a finger at you the customer. "Well, perhaps it is a lifestyle issue." Sorry, Apple, living in Wisconsin or Florida isn't a legit reason for you to dodge a basic engineering flaw!

People have blamed cigarette smoke, heat, pressing too hard on the LCD panel (which is just dumb; you're pushing against thick glass and can't affect the LCD panel at all with pressure) and a variety of other pet (and scientifically unsound) theories. It is so amazingly simple: its just the unfortunate collision of humidified dust and poor filtration. The reason Apple doesn't fix this is because they don't know how to properly isolate the problem and test. This isn't a conspiracy of geniuses...its a conspiracy of dunces. They aren't out to get us...they just don't know how to fix this. They designed a beautiful computer in a low-humidity environment and have never spent enough time on air filtration.

Email me.

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Feb 3, 2010 3:56 PM in response to Shaun Ragnauth In response to Shaun Ragnauth

I have it here too. With me it's very complicated though. I had screen problems on two earlier iMac incarnations (a 20 and a 24'') and both were replaced over two years when multiple replacement screens did not prohibit a recurrence. I can understand why they would question my environmental conditions and indeed warned me that if this newest imac ended up having "dirty, smudgey" stains they would not replace it again. I am not a naive or new Mac devote though and I promise you it is not environmental (no nearby cooking, well ventilated, not near a window, non smoker, etc) so I fear I will be on the far end of credibility when I call. On both previous iMacs and their myriad replacement screens it was on the upper left side. This stain of 1.5 inches is on the right side- right of the top center. I do not want to accept this new blemish. d

Feb 3, 2010 3:56 PM

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Feb 4, 2010 8:43 AM in response to Shaun Ragnauth In response to Shaun Ragnauth

I haven't contacted apple care yet (extremely busy), but when I do I'll post my experience on this thread. If you do please post your experiences as well. I have a feeling it's related to the "northbridge" heatsink. The upper left hand corner will get pretty hot when in use for a period of time. I just hope this is not a design flaw. We shall see.


Feb 4, 2010 8:43 AM

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Feb 5, 2010 5:12 AM in response to swapnonil In response to swapnonil

Just discovered the same thing on mine, top right has smudge marks from the inside. I also have a slight yellow tint on the screen at the bottom. I really don't want to give the machine in right now as it works beautifully apart from the screen no other issues. Though this is new machine just 2 weeks old its serial number is that of a week 44 one (India does not get a lot of love from apple). Thinking of waiting for known resolutions (for both the tint and the smudges) before taking it in.

Feb 5, 2010 5:12 AM

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Feb 16, 2010 10:04 PM in response to swapnonil In response to swapnonil

I have also noticed what look like heat streaks growing at the top left and right of my 2009 24" iMac screen.
The aluminum frame gets so hot at times that it's too hot to touch, except very quickly. Especially in the upper left corner, where the fan blows the excess heat.

I believe these screen streaks are actually burn marks made by the heat. They were not there at first, but they continue to grow as time goes on.

My fans all run at the correct default speeds for this model, but I believe the frame gets way too hot, and I think my screen has been damaged from the heat.

I am going to report this to Apple as well, and will report back with any new info.

Feb 16, 2010 10:04 PM

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Feb 17, 2010 10:34 AM in response to greenthunderleaf In response to greenthunderleaf

Same problem here with iMac 21.5 bought 1st Dec 2009.

With a week or so marks appearing in top left corner spreading inwards, and later more appearing around all edges.

Casing does not get hot, only mildly warm after long use. It looks like a static smear of very fine particles. Gradually increasing.

Still within the 90-day warranty, contacted Apple. Guy said he could only deal with software issues and gave me a number for local reseller who could deal with hardware problems.

Called them, they said this problem is not covered by warranty, I have to bring the machine in and there will be a charge to clean the inside of the screen.

Not happy. Very not happy. Is this going to be a regular trot for me?

And if I buy the AppleCare warranty - does that still not cover having these design defects rectified?

Not going to go away quietly on this. These machines don't come cheap.

Feb 17, 2010 10:34 AM

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Feb 17, 2010 10:43 AM in response to IanSn In response to IanSn

But it should be covered in warranty ? no ? I don't think theyre stains on the inner side of the glass, more likely burn marks on the screen or something. A screen replacement is the fix I think, which is covered. I'm not sure however I haven't given mine in, I do not have the time at the moment. I had requested a refund via email instead and haven't heard back from apple, and my dealer wasn't happy when I mentioned a refund, they're more than willing to fix the screen though and said its covered.

Message was edited by: greenthunderleaf

Feb 17, 2010 10:43 AM

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Feb 17, 2010 11:01 AM in response to greenthunderleaf In response to greenthunderleaf

At this point I don't know. Just reporting what happened.
Not in London at the moment so there's no store near me, bought it online.

Have to keep hassling Apple. Don't understand what this 'not covered by warranty' is all about.

Things are meant to be 'fit for use' when they are sold, or money back. That's the law.

Feb 17, 2010 11:01 AM

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Feb 17, 2010 11:47 AM in response to IanSn In response to IanSn

Have the same problem with my 21.5" iMac purchased just after release in october.

Didn't notice it in the first two months (had a dark wallpaper) but the smudge streaks, left corner, are getting worse.

I had the same problem with my old 20" iMac, matte screen, but that happened after two years (no Applecare then).

Guess I have to make a call soon, bummer.

Feb 17, 2010 11:47 AM

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Feb 17, 2010 12:22 PM in response to swapnonil In response to swapnonil

I recently bought a second-hand 24" iMac (less than a year old) and noticed the same screen staining being described here. Yesterday I took the glass screen off (surprisingly easy) and repeatedly cleaned the inside of the screen with a mixture of white vinegar diluted in warm water and also a light mix of window cleaning fluid. It took about four goes at cleaning, putting the screen back on and checking the results, removing and repeating the process. I can honestly say that so far as I can see the results are perfect. Whether this state lasts or not remains to be seen.

Feb 17, 2010 12:22 PM

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Question: Greyish Smudge marks behind the glass screen.