Screen Flicker with External Monitor

Not on a Macbook, but I get the exact same flickering problem with my U2711 connected to my mid 2010 Mac Mini Server with nvidia 320m graphics. Very annoying. Have tried all sorts of combos of adapters etc. Nothing works except to run it off the hdmi port at 1080p. Rather dissappointing.

I had this problem a few months ago. I bought a new display port to hdmi adaptor and it seemed to be fixed. Last weekend I moved my desk and cleaned my office and bam the issue came back again, sometimes.

I fiddled with cables heaps, I read heaps and I googled heaps more. Finally somebody on hear said they moved their iphone away from the monitor. Well as I turns out I had decided to use my keyboard usb ports after moving my desk to charge and sync my iphone. So I unplugged it and moved it away and so far so good no flicker.

So hopefully this helps. What is also different is they way I have my logitec 2.1 speakers setup so perhaps a combination of the 2 was causing the issue. Will have to wait and see fingers crossed. Makes you wonder though what apple do differently to PC because nobody reports this as being an issue with PC's and I am sure that plenty of them have their phones near their monitors.

Are you having this issue on a 24" cinema display? If so there is a firmware update for the display (earlier in this thread or another -- i can find it if you can't) which I'm 99% sure will fix the problem (not an update which comes through software update).

If it's a 27", then it's probably some other issue.

ozdeveloper wrote:

I had this problem a few months ago. I bought a new display port to hdmi adaptor and it seemed to be fixed. Last weekend I moved my desk and cleaned my office and bam the issue came back again, sometimes.

I am still having this problem.

I connect my late 2012 15" MBPro with Retina display to a mid 2011 21" iMac for use as an external display via thunderbolt. Both devices are completely up to date on software and firmware.

Randomly the iMac screen will go black for a brief second and then come back on.

This happens anywhere between 1-20 times in an 8 hour day.

It sounds like Apple is aware but most people seem to be reporting the issue with connections to an external monitor while I see it connected to another computer (although it's being used soley as an monitor).

Please fix this porblem Apple.

MY issue is that ANY cable inserted into the "miniDisplayPort" in the back of my iMac causes the screen to do one very brief horizontal flicker (I call it a "blip") about 2 or 3 times an hour.

I have used SEVERAL different cables in the mini DisplayPort to connect various monitors; after trying different cables, different secondary monitors, etc., I have determined that ANYTHING plugged into the back of my iMac causes this intermittant "blip."

In a nutshell, I recently did a little "test" as follows: I purchased a simple small miniDisplayPort extension cable. Without attaching any monitors or anything, I just stuck this cable into the back of my iMac and let the 12inch cable hang there. SAME THING: the intermittant "blip" happens 2 or 3 times an hour.

Any ideas?

Hi, I have the same issue on a Mid 2012 MBP and an external Apple Cinema Display 27". What I found out was that it seems to be the connector itself. If I open a black terminal, I can see white pixels flickering, too. If I move the connector a little bit left or right or so, it stops flickering. After that the screen is completely stable. So it seems the connector is somewhat sensitive and you need to find the "right" position. That workaround is working for me.

I do notice that if I switch to a lower resolution the flicker/static is not as severe

@ ozdeveloper… I'm with you on this one.

I was going nuts for days/weeks !!! with intermittent flickering on a 2nd monitor connected to my iMac 21.5".

Buying new cables, shielded power strips, etc, etc…

One day, it suddenly stopped flickering at all.

Then I realized that I had left my iPhone4 out in the kitchen.

I usually have/had it propped up in front of me on the iMac.

Ever since I realized this, no more flicker, nada, never !!!

Old thread, but this issue drove me crazy for a few weeks. I had a 24" HP monitor (1920x1200) connected to a 2013 MacBook Air via Thunderbolt/MDP to VGA adapter. First, I noticed that the flickering was not there at lower resolutions. I went to an Apple Store later and got the Thunderbolt/MDP to DVI adapter which completely fixed this issue for me! Steady image, no flickering at all! Hope I could help!

Nice Graeme, that seems to be what was happening in my case as well.

thanks for this, i was getting the flicker when the second display was connected by HDMI, but the HDMI input was not selected on the TV.

I adjusted the refresh rate from 60 to 50 hertz and now i don't get the flicker when the second display is switched off

At the end of 2014 I started getting this problem with an external monitor attached through the thunderbolt port. Same problem both with Apple Cinema Display and a Samsung.

I can't say for sure, but I think it was with the Mac OS Yosemite 10 release, or the .1 update.

Have yet to reset the PRAM, and can't - nothing happens....

(I've password protected the firmware, can log in to the recovery partition, but can't disable the password because the Mac says it's wrong, so I assume that's why I can't reset the PRAM)

I’m experiencing quite alike problem.

For about 9 months everything was ok, but now my external 24’’ 1920x1080 Samsung monitor blinks, shows «white noise» and other graphic artifacts. Very annoying!

I thought that it’s a hardware issue, but when I booted to Bootcamp’ed Windows OS, I got not a one blink! None of them! So it’s completely software.

External monitor can work very good for hours, but then suddenly begins to blink. Especially annoying when watching videos.

I tried to reset SMC and PRAM, but neither had any effect. Also I tried to boot in safe-mode with same flickering, and even in «OS recovery» mode, but that **** flickering appears even there!

I’m sure that the root of this is somewhere in SMC, but cannot find a solution.

Pls help 🙂

just went to this link you suggest:

Not Found

The item does not exist. It may have been deleted.

nope. not for me. moved it away and then powered it down.