You can make a difference in the Apple Support Community!

When you sign up with your Apple Account, you can provide valuable feedback to other community members by upvoting helpful replies and User Tips.

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 10:46 PM in response to latVm

Hi,


This problem is not rectifiable unless u change the Display hardware from apple, which is super expensive and still doesn't guarantee that it'll last perfectly after change... so no point !!


So next step is to get an EXTERNAL MONITOR.

Since most of us are so used to the iMac 5k screen monitor... it becomes difficult to adjust overnight to some other monitor... so here's the thing....


iMac M1 2021 model comes with the PPI (PIXEL PER INCHES)- 218 PPI

I stay in Bangalore, India and recently got a Dell QHD monitor for 23k with resolution QHD (2560 x 1440) with 109 PPI and it's so hard to get used to this screen... since suddenly ur PPI has dropped to half from Mac's 5k 218 PPI to Dell's 2k 109 PPI. You might see the Videos and pics quite clear... but when it comes to TEXT CLARITY... u will not find it easy for your eyes... as the clarity differs a lot (attached screenshot from my Dell QHD monitor below... as u can see the text is pixelated and not-so-clear).


Now imagine the text clarity when u try and buy a 1920x1080 resolution monitor... which will have below 100 PPI display quality.... hence the text readability will be still worse.


So my suggestion is to go for a 4K monitor which comes with a higher 163 PPI display for a better TEXT clarity on screen.


My current DELL QHD monitor costs me 23k and the next version 4k monitor costs 30k upwards. I'm now forced to return this QHD monitor and go for the EXPENSIVE 4K monitors... bcos Mac won't do justice to the display screen with lower PPI :(






May 19, 2024 11:21 PM in response to latVm

Same situation as well, bought mine in September 2021 and the lines started to appear in March 2023. At first I thought it was just me but seeing all the responses here, this is clearly not an isolated issue.


Was putting off sending it for repair since I was hoping the display will go back to normal by itself over time, since the lines tend to flicker and on some days they take up less of the screen.


However in April 2024, it got so much worse with the lines completely taking up the display, rendering it impossible for me to navigate or even use the computer itself.


Would like to ask if there’s a recommended adaptor or cable to connect my M1 iMac to an external HDMI display so I could access and back up my files? Much appreciated!


May 20, 2024 2:29 PM in response to latVm

I have the same problem after 3 years of use. My iMac has been used carefully and everything works normally except for those black horizontal lines at the bottom. Apple, please!!!, help with this. We have relied on the quality of your electronic products when making these costly investments and I understand that it is not fair that you leave us stranded in this way.

Jun 11, 2024 1:42 AM in response to latVm

I'm having the same problem. I called apple service in South Korea 3 times and went to apple genius bar, but they couldn't solve it and only recommended paid repair. They asked for 850,000 won, which is the same price as a used M1 iMac. I used the iMac in a fixed position and didn't do anything to cause it to break down, it's so unfair. I don't know if I'll be able to buy a Mac in the future.

Persistent horizontal lines appear on iMac screen

Welcome to Apple Support Community
A forum where Apple customers help each other with their products. Get started with your Apple Account.