Q: Greyish Smudge marks behind the glass screen.

I have a 27" and this has happened to me too. No direct sunlight, pretty dust-free house etc. Mine is also out of warranty. Anyone had any luck with getting this fixed by Apple free of charge?

Have any of you got a laser printer near the iMac?  Here's a theory, laser printers can emit a small amount of dust during a print, this dust is attracted to light/heat, the dust is sucked into the iMac by the fan, some screens are not properly sealed and can be contaminated by the dust as it is attracted to the backlighting. Logical?

Having taken mine totally apart, I can tell you it isn't dust (I pointed this out earlier in the thread).

It's a dismal mix of shoddy construction, third world quality standards and bargain basement design. Par for the course with this company now.

Besides, if this machine really is that sensitive to everything, it shouldn't have been on sale in the first place. It wasn't fit for purpose and hadn't undergone any testing.

I just took my 27" 2010 Imac, last month for a recall from Apple for the faulty Seagate Hard Drive. I mentionned the display while I was there and the Genius just added the job without any discussion. It went under "apple quality Program" or some sort. Nothing to pay (I never took the Apple care plan as all my Macs worked over and over...until that one) and I have a new display !

Thanks Apple !

Good for you!

You are lucky! I had the same problem on my 27" iMac and had the screen replaced under Applecare warranty.

I did not pay anything, but I did see the bill.

The total cost for the new screen and labor was $750.00!

And I can confirm that it is NOT dust of any sort.

It's a defect in the LCD screen itself.

Yes it is dust, it's fine dust that is contaminating the LCD panel. The only defect in the panel is that it's allowing the fine dust into the panel.

If its not dust, then I'd be interested to know what it is Eric.

I don't know if it's dust or not, but I thought MacDalion's info below was an interesting theory (or proof positive depending on if you believe the Apple employee). I've also read in other DIY iMac screen threads (MacRumors comes to mind) that the "particles/dust" inside the screen didn't look like ordinary household dust:

MacDalion wrote:

 

IF ANYONE WANTS TO FIX THIS: check my 2012_11_04SUN post.

I didn't want to add anything else but: some days after that DIY tutorial post an APPLE assistant told me that he had heard this problem is due to the existence of a glue paste which, when heated up, generates that dust. Now that's an info I hadn't found anywhere... I wish he was wrong but I must say that the dust I found inside the LCD panel did seem to me finer-grained/powderier than plain house dust...

It's quite embarrassing to see such ridiculous blind faith in Apple and their repair technicians. It seems you'll all believe anything they tell you.

Open your own machines up and look for yourself, the problem is rather more complicated.

I'd be interested in seeing the genius bar receipt. I'm having lots of problem with my 27" iMac still under apple care warrenty. Can you pm me?

Was using my iMac and suddenly realized there's these 2 mysterious circles in the middle of a cloud on the LCD panel.. Anyone any idea what is that?

I purchased a new iMac 27" when they first came out in the fall of 2008 or was it 09?

My three year apple care has just expired and today, I see a few black smudges on my screen.

It is really sad to get this kind of thing from apple

As a developer, bringing my machine into the store is a huge burdon but I guess it has to be.

Apple emailed me a few weeks ago that I get a free hard drive and it would be nice if they fix their poor quality screen as well.

If not I will think long and hard to move to windows 7. By now, it should be ok to do webdesign on such a machine?

I will post/update after I call the apple store tomorrow.

VERY disappointed in the iMac and my iPhone which also has issues with the slider.

People, you do not have to lug your iMac to the Apple Store or Authorized Technician. Request on site service. It's part of your AppleCare. Of course they may try to persuade you to lug it in.

I went through 3 LCD replacements and then Apple gave me a new iMac. I wanted to go with something else like a mini and thunder monitor because I knew this was a common problem. They wouldn't hear it and I thought I better shut up as they were giving me a newer iMac. I now have the same issue with the dirty cloudy like screen but it's progression has been much slower than my last iMac. These are 27" iMacs. First one around May/June 2010 and the second one in December 2011. So I'm still on the initial LCD and it's been a year. I just purchased AppleCare for my current iMac because I know I'll be needing it.

It is very dissappointing, but I predicted they would have shielded the screen properly in the the new imac redesign. And I think they did, leaving thousands of 2009-2011 iMac customers to deal with these older defective machines. I'm sure their next propostion will be to just suggest to us that we upgrade to the new iMac. But the better solution here is for Apple to offer some sort of a trade-in. However, from what's happend so far, with everyone's Applecare expiring, that propostition is highly unlikely. There's lots of activism going on online on this issue, so just google it to get involved.

Lain MacDonald1,

It's probably a defective component in the LCD panel, or something generating excessive heat behind the LCD could damage some of the pixel cells.

I had mine replaced and the first time the Apple technician came to my place to do the work, the screen she brought with her was showing the same problem the minute she installed it in my iMac.

The inside of the iMac was clean and no dust was found on the original LCD.

She came back a week later with a new LCD and installed it. It's been working fine since then. No sign of the problem anymore.

Now there as been a lot of people complaining of similar problems. So maybe it was dust for some of them, but I don't think Apple would replace LCDs because there was dust on it. They may agree to clean it, but replacing it! I don't think so.