Greyish Smudge marks behind the glass screen.

Thank you for sharing your story. I'm now on my 3rd LCD with Apple giving me a line of bull, etc. etc. I had made a big deal about my new 27" iMac to my PC user friends. It's less than 2 years now and I know I'll need a 4th LCD or something soon enough.

I spent an hour discussing this problem with an engineer who has experience with LCD panels. Here was his conclusion:

ENVIRONMENTAL FACTORS IRRELEVANT WITH LCD PANELS
1.) The individual cells of an LCD are sealed.
2.) Dust does not effect LCD cells.
3.) Moisture/Vapor/Humidity/Water do not effect LCD cells. Since the cells are sealed there is no way for water of any kind to enter the cell. In fact, he's submerged LCD panels in water for 4-5 hours (to remove various protective layers from the panels) and then turned them on after they've dried.

SMEARING/SMUDGES ARE CLEARLY CAUSED BY EXCESSIVE HEAT

The engineer looked at the various photos on this thread as well as my iMac and without skipping a beat he said "Your LCD panel is too hot." I asked him if he'd ever seen this before. He responded "Oh, yeah. I've accidentally exposed LCD panels to a heat source 4-5 times and caused this exact problem. The individual cells contain liquid crystals. If they're exposed to excess heat and begin to boil these smudges are the result. It gets worse over time because the panel is consistently being subjected to overheating causing more cells to boil and leak. This stuff is really simple; dead cells are black, working cells emit a full range of colors and cells that have boiled off some of their fluid are grey. What you have is clear, obvious, scientific proof that the LCD is being overheated, that the cells are boiling off some of that fluid, the cells are bursting and the fluid is staining the inside of your panel. The only way to fix this is to redesign the iMac."

QUALIFICATIONS OF ENGINEER
My engineering partner has worked professionally with LCD panels for over 5 years. He's personally assembled over 500 units that required custom LCD panel installation. He is a professional engineer who previously worked for Bell Labs as well as private firms with military contracts. He has experience in electrical engineering, electronics, optics, IR and projection.

CONCLUSION

I'm now convinced that the iMac has serious overheating issues and that it is cooking the LCD panel.

Anyone who has ever been told their environment is to blame has been deceived. Smoking, dust, a clean room, humidity...none of these are factors when dealing with a technology sealed from the outside world. Heat and heat alone is the culprit to this issue. This is a design flaw in the iMac. It deserves a recall and a redesign.

Very interesting post! Thank you for sharing.

However, I'm confused as to how some (very technically proficient!) folks have shown images of a fully-disassembled LCD screen (separating the screen from the backlight) and literally "wiping off" the particles that are causing the smudges... when I read "...the cells are bursting and the fluid is staining the inside of your panel", I'm just trying to reconcile what appears to be cleanable (with proper disassmebly and handling) with the description of your engineer which sounds like more permanent damage to the display. Unless I'm reading that wrong?

Or, phrased differently.. I didn't think any of the LCD cells were damaged, but rather just some kind of dust/particles made their way between the LCD and the backlight?

OMG, that's even worse than dust particles or condensation. But it makes sense. I think a lot of the problem is Apple tried to stuff all the hot internal hardware right next to the LCD.

I'm wondering though, has anyone had these same issues with Macbook Pros or with the 27" Cinema Thunderbolt displays? Or is the heat dissipation of the motherboard on just the iMac the issue here?

Binary Mango -

Could you please point me to the specific posts you refer to? I've read this thread thoroughly and I'm struggling to find them. I see pictures of smudges exactly like mine. I see dozens of posts where people have been told by Apple that it is an "environmental problem" and refuse to repair it. I see posts from people like DeepRoot who has experienced exactly what I've experienced; Apple replacing the LCD panel of our iMacs for free. I see plenty of messages from people who have been accused of living in unusually dusty environments. But, I don't see any posts like the ones you refer to but fail to specifically reference.

And there is my extensive story. Two panels replaced and an entire iMac...and the problem has returned for the fourth time.

However, let's entertain your hypothesis. This would mean Apple has now spent thousands of dollars on replacing my LCD panels, an entire iMac, retail staff wages, manual labor, shipping costs...all for something they could have fixed with the wipe of a cloth? That's an irrational conclusion.

It also isn't supported by the facts of my case. Nor the other cases cited on this thread. The majority of people on this very thread fall into two camps: people who complained and have had their LCD panels or iMacs replaced and people (primarily in Asia) who have complained and been told it isn't Apple's responsibility.

Dust doesn't look like water. Ever. Dust looks like dust. These smudges/water spots/stains are so fundamentally different than how dust behaves or reacts with electrical components that it borders on a flat earth argument. More importantly, the exterior of an LCD panel is not conductive. The cells are also sealed. So there is no way for dust to interact with anything inside the cells of an LCD panel. It is a scientific impossibility.

The panels do react to heat...something computers are quite adept at creating.

Omek -

I own a Macbook Pro, Macbook, iPad 2, (2) iPod Classics, an iPod Touch and an iPhone 4S. This problem hasn't appeared on any of those devices. Nor would it; the LCD panel on a laptop is completely separated from the heat-generating components of the product.

I had a Cinema Display and never had this problem. However, that also lacks the built-in computer components of an iMac. A Cinema Display is just a monitor.

To me, it is quite clear why this problem only effects iMacs: because the iMac's computer components are in direct proximity to an LCD panel that doesn't react well to high temperatures.

This thread has grown too large for me to search through, but at some point these images were either posted or linked:

http://forums.macrumors.com/showthread.php?t=1101370&page=2

Specifically this one:

http://forums.macrumors.com/attachment.php?attachmentid=287668&d=1306956612

And as you can clearly see, this person is wiping it off and "solves" his problem. It's important to note just how involved this "fix" is... the average user is probably not going to go this route! And neither would I as long as my machine is still under warranty.

Hopefully you didn't confuse my post as defending Apple's handling of this situation... I'm in the same boat as everyone else here and I have to decide whether to live with my smudge marks or continue to get my machine serviced every few months! My only point is that the person from the links posted above is able to clean the internals of his machine. From your engineer's description, and from your most recent response, I would be surprised if that kind of LCD damage was "cleanable".

That's exactly what I'm assuming as well. I have the original late 2009 quad-core i5 iMac, and the staining just started happening. I tolerated the 1/3rd yellow tinge on the bottom, but this is just getting ridculous. This machine has had so many issues.

We also have an ipad, and it doesn't have any of these issues.

I did hear that some people where noticing the same yellow tinge on the lower 1/3rd of the 27" Cinema display that is also prevelant in iMacs. But, I'm still not sure if that issue is heat-related or not.

Apple clearly must be aware of this stain issue, but they just don't want to do a recall. And like your friend said, probably the only thing that is going to solve this problem is if Apple redesigns the iMac. I'm thinking the best solution for now may be to sell or trade-in for a Macbook Pro or mini with an external monitor. I think this problematic iMac is just going to get worse and worse. The longer Apple waits to recall this iMac, the worse the aftermath will be.

Binary Mango -

The image you posted is of dust. Notice that it looks like...dust. Not water. Dust.

The images posted by 99% of the people on this thread looks like water. Hence the reference to a "smudge" or "water stain."

Here is a link from the second page of this thread:

PHOTO OF WATER STAIN NOT DUST

I'm not sure why I feel like we're arguing over this; maybe it's because you believe with 100% certainty what your engineer told you, and that's fine. But honestly I believe that the "dust / stains / smudges" are in fact all part of the same problem, just described differently by different people.

Have you taken a close look at the "dust" in this one photo?

http://forums.macrumors.com/attachment.php?attachmentid=287668&d=1306956612

Do you see how it looks splotchy/smudgy? I could absolutely see how some people would confuse this for a water stain. In fact, look at the first comment from user "iammike1" on top of the thread I posted before:

http://forums.macrumors.com/showthread.php?t=1101370&page=2

He writes: "Mine wasn't dust. Was kinda difficult to wipe off. Almost reminded me of water stains which I guess could be possible if condensation got in between the panels."

So, I'm not saying it's dust, it might be some fine particle from something that was melted/separated inside the display as a result of the heat. But what I am saying is that people are able to wipe this off, albeit not always easily. My point in all of this; the "moderate" cases I've seen do not appear to be permanent damage to the LCD's but are clearly beyond the ability of an average user to clean, and will void an active Apple warranty if the screen is disassembled anyway. That's a far cry (to me) from what the kind of damage your engineer was describing.

I'd appreciate a little less condescending tone if you'd like to continue this discussion. I'm not the enemy here, nor am I a child or a complete stranger to the problem that has been plauging my iMacs for the last year or so.

Binary Mango -

And yes, I was defensive because you came across like a shill for Apple. Perhaps starting with "I have a similar problem with my iMac" would have helped. In addition, the references you have are for a completely different thread!

I come from a place called Rational Land. We do things differently there. First, when we cite sources. Second, when we say a thread has "all sorts of examples" we don't assume other people are mind readers allowing us to refer to a completely different thread. For example, if I'd seen the thread you were referencing I might have been less defensive and given you some credit; that thread and the detailed photos are quite useful. Based on that series of photos it is entirely possible some people on this thread have a dust problem instead of a heat problem.

Now that we're back on track I think it is fair to say that whether someone has so much dust in their LCD panel that it is creating streaks or that heat buildup has caused wet-looking smudges on their LCD panel that both are unacceptable design flaws of the iMac.

Computers should not be disposable goods. With these flaws the iMac most definitely is.

I cant believe the amount of people with this problem. I thought I was the only one. I don't know how long it's been there but I just noticed it. It looks like a black smear in my corner. Driving me nuts! They said it is out of warranty and it's an enviromental problem. Give me a break. Last Apple product I ever buy.

If you have a problem with your product just admit it.

Hi Tim,

If you haven't already, be sure and check out the first search result in this Google link:

https://www.google.com/search?gcx=w&sourceid=chrome&ie=UTF-8&q=imac+screen+chang e+org

Welcome to the club!

I've had many different mac's over the years... 3 different imacs are amoung them. I can tell you that all three imacs were affected by the smudges and yellowing. My current imac also has this problem. I can also tell you from experience IT IS DUST inside the display. On 2 of my previous imacs I actuall took the screen off... split it in half to get between the LCD and the other reflector's and polorizers. I did infact manage to clean them off and restore the screen to no smudges... HOWEVER this is not for the inexperienced. And if the screen has been "warm" then the connections on the surface mount ribbon's are brittle and you will develop lines and missing pixels in your screen if you bend the ribbon's taking the screen apart. I also have noticed the ribbed reflector which is made of a white plastic was yellowed by heat. I was unable to completely remove the yellowing. However, that stuff that you use to polish headlight lenses on cars mostly did the trick removing the oxidation. The bottom line is that the fans draw dirty air into the display because the edges are not completely air tight. The stand alone displays do not exhibit this problem because they are not vented with fans. When re-assembling the screen if you get even 1 piece of dust between the reflectors and the LCD it will drive you insane.... This whole process shold be done in a clean room.... All it takes is one day to cook with grease and that stuff get's inside your machine and then being sticky... the grime builds up.....Usually becomes noticible during the second or third year depending on how much you use your machine. I use mine ALOT they're nearly on 24x7 so they develop the smudges quickly even though our home is cleaner than most.

Welcome to the club folks... just ebay your imac every couple years and you'll be fine... they do have a decent re-sale.

Hi Beddo,

I'm experiencing the same issues with my 24" iMac, and need a couple of pointers with regards to baking the GPU and applying the thermal paste. I've disassembled everything and am a few steps away from baking. Please respond to me if you see this.

Thank you!