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Persistent horizontal lines appear on iMac screen

I am reaching out to share an ongoing issue I, along with several other users, have been experiencing with our iMac 24-inch models, and to seek a collective resolution.


Problem Description:

  • Persistent horizontal lines appear on the screen, which significantly hampers the usability and visual appeal of the device.
  • This problem arises without any physical damage, and despite the stationary nature of the device.


Steps Taken:

  • Connected to an external display: The external display works fine, indicating the issue is with the iMac's internal display.
  • Reinstalled the OS: The problem persisted post reinstallation.
  • Avoided operating the iMac for a week: No change in the situation.


Concerns:

  • The cost of screen replacement is high, and there's no assurance that it will resolve the issue permanently.
  • The quality concern is alarming especially for a brand that positions itself as a premium segment player.
  • The support received thus far has been unsatisfactory, with no definitive solutions provided apart from a costly screen replacement suggestion.





Please do not ask us to visit to service center and replace the screen for 650USD + , problem happens mostly after warranty.


[Edited by Moderator]

iMac (M1, 2021)

Posted on Oct 21, 2023 10:40 AM

Reply
Question marked as Top-ranking reply

Posted on May 19, 2024 8:45 PM

According to the Apple support team I contacted, it's an LCD malfunction and the only solution is to replace it.


What they didn't say was why this problem is occurring after two years of using the iMac on so many computers.


So, as Apple hasn't yet assumed that it's their fault, what I did, given the lack of concrete answers from Apple, was to take my iMac to a technician and ask him to assess the problem to see if it's a construction problem or just a random fault.


The explanation I was given was as follows:


In terms of circuitry, everything seems to be working properly.


The problem, apparently, lies in a cable that also powers the LCD, which is located on one of the tops of the screen, and which, in order to be replaced, requires detaching the screen glass from the LCD itself, which is a very sensitive operation and almost impossible to carry out without damaging the LCD.


So the only option is to replace the entire LCD (LCD+main boards+screen glass).


Also, according to the technician's explanation, this cable (of the FFC/FPC type or Flat Flexible Cable / Flexible Printed Circuit), it has to sustain a very high voltage (around 50V) to power the LCD (this despite the iMac's power supply being 15.9V), and it heats up a lot!


So, what happens after a while (in this case after about 2 years) is that it starts to burn out and degrade at the connector, to the point where it lets the signals leak between the various connectors and short-circuits some of them, which ends up causing those lines that we are all unfortunately familiar with.


The level of brightness makes a fundamental contribution to this problem. Thus, the higher the brightness used, the sooner the problem occurs.


This is easily understood by measuring the difference in temperature at the top of the screen when it is at its lowest brightness level, compared to when it is at its highest. It's quite a big difference!


When it's at its lowest brightness, it's practically room temperature; when it's at its highest, you can almost "fry an egg"!


I think that as soon as Apple recognizes that there is a problem with these computers, the first thing it will do is make a change to the OS that reduces the maximum brightness limit allowed (to less than 500 nits). Time will tell...


Why does this happen?

For at least one of three reasons:

1- a design flaw - so this problem is likely to occur in a large number of devices;

2- a defect in components - the problem is limited to a few cases;

3- use of components below Apple's standards - the problem may be limited, or more widespread.


This was the explanation I was given. I'm not a technician. Only Apple will know the exact reason(s).


If I had to guess, I'd say that I don't believe it's a design fault, because Apple has an obligation to be very careful about that; I also don't think it's a fault with the component(s) because it seems to be happening all over the planet and doesn't seem to be localized; so I think it's due to the use of component(s) below, or at the limit of, Apple's standards which, when put under extreme stress (higher brightness), end up failing.


I think it's already clear to everyone that this is a design or manufacturing defect in this Apple model.


So let's hope that Apple takes on this construction problem and repairs it or at least contributes part of the cost of the (overly expensive) repair of our computers.


If it were a car, surely all our computers would be called into the workshop to replace the component that has broken down or is in the process of breaking down.


As it's a computer... let's hope that Apple will behave in a way that suits its customers, who believe in the above-average Apple standard...


So keep presenting your cases to Apple.

Similar questions

271 replies

Apr 20, 2024 5:49 AM in response to latVm

Hi there,

I'm having the same problem with my iMac. While I'm on a video call, my screen suddenly doesn't look right, like it's covered with a screen. Tried restarting, updating the system, and safe mode to no avail.


I bought it in the UK in September 2021. The specific model is MGPH3B/A. iMac m1 4 ports.


I was originally going to follow the advice of Apple customer service and take it to an Apple store. Thank you everyone for your comments, which saved me a time-consuming and labor-intensive journey. Replacing the screen is really expensive. I'll probably look for any replacement monitors with a similar resolution to the iMac.


Hope to see any updates.

Apr 26, 2024 12:49 AM in response to RajaniN

UPDATE:


Got in touch with Apple Support; they asked me to take the backup of the Mac and start it in safe mode. Since the issue continued, I reinstalled macOS (Sonoma 14.4.1), but the problem persists.


Then Apple Support asked me to book a reservation at the Apple Store for their technician to check the iMac. They couldn’t check the price estimated for the screen repair. Of course I don't have AppleCare.


I am getting an inexpensive Samsung 1080p monitor and an Amazon USB-C Digital AV Multiport Adapter. I’ll connect the external monitor and continue using the iMac with the lowest brightness.

May 14, 2024 6:29 PM in response to JuanMunoz

nope, if you tried replace it from outside apple service center or another AASP (cheaper price) you will loose true tone feature (on your new display that you replace) it's because need some system configuration from the Apple (it's apple secret) and it will happen and all Apple product (with the display of course), and something you need to consider is, will this happen again in two year after you are replace it?

May 18, 2024 4:25 AM in response to latVm

Same issue here. iMac M1 2021, pre-ordered it. I've taken the best care of it, after all, it's just sitting on a desk. Seems like the display just spontaneously failed. This happened a week ago.


I don't know if I should replace the screen, because what if it happens again? I'm afraid it's the problem with the design of the screen and/or the computer itself, therefore a replacement may not completely fix the issue in the future.


Can we please get a response from Apple? This doesn't seem like it's an isolated issue, as evident from this thread. A lot of people are having this same problem. This makes me think it's a problem with the design or the manufacturing process.

May 25, 2024 12:09 PM in response to michielfromwinterswijk

From what I've been told, the problem isn't with this cable (which connects between the iMac main PCB and the LCD PCB and would be easily replaced) but with the cable that connects the LCD PCB to the LCD itself.


And to access this cable you have to peel back the LCD glass, which is difficult and easy to damage or break.


That's why Apple's solution is to replace the entire LCD...

Jun 10, 2024 7:46 PM in response to latVm

My Imac which i bought in August 2021 started showing this grey flickering background from about halfway of the screen to the bottom. I have done diagnostics and there is no software or physical damage to it. I am reviewing for my exams and this is so very untimely and very annoying to put it lightly. I trust apple products so much that all devices are apple. What can you do about this? We have all been here asking for your help. This is a a faulty model from your end not ours. I have been very careful in using my imac for the 2.5 years that i have it.

Jun 20, 2024 9:01 AM in response to latVm

Hi,


A bit of hope : my screen fixed himself 2 months later. I was using excell and the bugged lines were blinking when i was scrolling down. After some hours, the bugged lines entierly disappeared. But if the screen is turned off, the bugged lines comes back again. It seems the screen need to be warm to work well.


To fix it again, i open excell and let it on. I don't Know if it's the solution or not but doing it, it works... 😅


This bug happened since apple made their uggly and useless animated screensavers. I wonder if there can be a connexion.



Jun 20, 2024 2:39 PM in response to Luntzzz

Dear Luntzzz,


Our problem is definitely a hardware problem (with an FFC/FPC type cable). Apple has no solution other than to replace the entire LCD.


That's what's been happening.


The (very expensive) out-of-warranty repair has always been paid for by users (those who choose to fix it).


...With the happy exception of one case, already reported here on this forum, who managed to present his case to Apple and have his complaint (deservedly) recognized by Apple, even out of warranty, which provided a complete replacement of the LCD. Unfortunately, this has not yet happened with our other cases, even though they are the identical ones.


Your problem, given that you've fortunately solved it using only a spreadsheet, appears to be a software problem and not a hardware problem.


If it turns out to be the same problem as ours, I can guarantee it won't get any better. It will only get worse over time.


...And not even a Microsoft spreadsheet will help you... 😅

Jun 20, 2024 3:25 PM in response to Jotap62

Dear Jotap62,


"The (very expensive) out-of-warranty repair has always been paid for by users (those who choose to fix it)."


Agree! We will want to fix the problem. Since most devices are out of warranty, one must pay for the repair or replacement. That's a valid point!

However, buyers who have paid for their devices need some response from Apple. I am sure no apology, acceptance or roll-back may come from their side! Nevertheless, a simple reaction like 'we made a mistake' will do. This or that way, every buyer wants to move on rather than staring at the faulty screen dancing and flaunting the 'careless' moves of Apple, the company that somehow manages to have many screens worldwide failing to the same issue! That is why this visible anger is appearing here.


Jun 21, 2024 3:56 AM in response to latVm

I bought an imac m1 2021 and black lines started appearing then eventually this weird blotch of purple color started showing on the top left hand screen. Then it gradually got worst to the whole screen is black and the computer is unusable. I also noticed a burn mark up in tge left side of the screen where the putple blotches of color was. I just read someones post that took his computer with same problems to a repair guy to get a diagnosis of it and said something like there is a faulty cable that overheats so this explains it. Im really angry as Apple told me that can’t do anything because it’s out of warranty. I’ve been using Apple for decades and I always take care of my equipment. I use it for work feel really cheated because this computer was defected from the beginning. There was so many issues.

Persistent horizontal lines appear on iMac screen

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