IMac Display is jittering or subtly flickering

i just bought a iMac off of eBay. 2ghz Intel Core 2 Duo. One of the white ones from i think three years ago.
the last couple of days the display has started to faintly have those ghost lines jittering. i wish i knew the best way to describe this.. it isn't related to the hard drive, because it happens on both of mine- external and internal.
i'm just wondering if anyone else has experienced this, if it is a known issue, and if there is any fix for it. thanks

i just reset the PRAM. that seemed to do the trick.

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Intel imac display glitch and involuntary restart

Just want to know if anyone else has experienced this specific problem, there are plenty of complaints about intel imac displays but I can't be bothered to sift through them all trying to find a match for my problem.
A couple of months ago I was watching a video in quicktime and noticed that my screen was glitching and flashing fragmented diagonal lines - like a commodore 64 loading type thing. Then the spinning-ball came up and a force quit didn't do anything so I had to force shut down. I started up and it occured again. Then the screen went blank/black, but still lit up, and restarted without me doing anything. It also got stuck during start up the second time this occured. I panicked and ran out to buy a 500GB external drive, backed up all of my work and then re-installed mac osx from disk, archive and install job. This seemed to sort it and for the following two months it seemed OK. No sign of any problems.
Since then I have updated from 10.4.7 to 10.4.10 (which I have suspicion that it screwed the firmware in my motu 828 firewire audio interface, costing me a £130 repair - but that's another painful story).
It happened again tonight (the screen thing, not the motu). And the ball came up and I couldn't do anything. Force shut down, restart - screen glitching again. Then I had 2 unexpected restarts, one getting stuck in startup. Then a successful startup but accompanied by the glitchy graphics, mainly red/pink pixellated diagonal lines flickering in and out. I ran a disk first aid - no problems. Did a disk permission repair. Shut down and ran a hardware test, the first few minutes of the test the screen was still at it but then stopped glitching, hardware test found no errors (it was an extended test too). Now I'm back on it and it's all OK.
Any suggestions/similar stories?
When it occured 2 months ago I had the original ram that came with the imac. Now I have 2x1GB sticks of crucial ram.

That's it! Well, that's what I have. Unfortunately, I don't know about the cause, but I don't ever recall having it prior to an update going back about a year ago. I recall an update, and that update being immediately followed by some sort of Apple Graphics something-or-other. I feel pretty certain that's when I first noticed this. I just had my LCD replaced for another reason, but I think you'll agree, it's not an LCD issue. In my case, browser activity, scrolling up or down in a page, seems to be the most common trigger. I've also seen "pieces" of the torn page, on the screen when minimizing the browser to the dock (usually Firefox, but I think I've seen it with Opera and Safari too). Is there a way to find update packages installed somewhere? I'd know it if I saw it, and I'd definitely try removing that suspect package/update.
Message was edited by: geekboy2000 - corrected OS

IMac display mirroring

I have an iMac G5 which is having some issues with video mirroring. When I try plugging a TV into it via the Apple video adapter, the imac display flickers, indicating it has adjusted to the new display, but there is no image on the TV. The System Preferences indicates that there is a "VGA Display" attached. (I believe that is supposed to say "NTSC/PAL." That is what my PowerBook says in any case)
Now however I have a new problem. The Apple Video Adapter is unplugged but the iMac still thinks that the "VGA Display" (actually the apple video adapter) is plugged in. It is stuck at a certain resolution (1028x768) and if i put it at a higher resolution it still shows only 1028x728 pixels, except now they are in the middle of the screen with a black border around it. (I believe this is normal behavior.... for when a TV is actually attached)
Any ideas? Both for the first problem (iMac thinks TV is a VGA Display) and the second (iMac thinks there's an external display attached when there is not). Thanks.
iMac G5, 1st Gen 1.8 GHz 17" Mac OS X (10.4.4)

Im having the same issues and would like to know if there is a solution...its driving me crazy!

Imac display brightness has dropped

For the last few weeks, my 27" imac (2011) has been experiencing random flickering where the display would flicker between it's set brightness and medium brightness, but it was never something that I would be able to predict or trigger. Then last night my display flickered and and stayed dimmer.
The display is still visibile and backlight still works, but at full brightness in a fairly dark room, the display is now noticably dimmer than it was before, where before hand in a dark room it was necessary to drop the brightness to below half to where now it is just right in a dark room, but in a lit room the display isn't quite bright enough. Basically the display is not as bright as it used to be, any idea what it could be?

Laundry Beach mean resetting the PRAM. You can find directions by clicking Intel iMac SMC and PRAM resets

Imac display flickr and double picture

I have a 27" iMac that i have had for just over the 90 days of phone support. The display just started flickering and showing a double vision about 1 inch above where things are supposed to be. The apple rep when I called in said it was likely a software issue. Ive tried the imac display firmware update but it says that it doesnt need to install it. Does anyone have any other ideas on how to fix it?

HI,
Run the Apple Hardware Test from your install disc just in case.
Intel-based Macs: Using Apple Hardware Test
Try Resetting the PRAM
Carolyn

Some times my new iMacs display start flickring when I starts playing a game. I am very annoyed. I have bought it only 1 month ago. What can I do?

Some times my new iMacs display start flickring when I starts playing a game. I am very annoyed. I have bought it only 1 month ago. What can I do?

A flickering display sounds to me like a hardware problem. Or does this only happen with a specific game? Of course your machine is still under warrantee so you could take advantge of it if you have a local apple store.

Putting iMac display to sleep, when using TV as a screen.

I have just connected my iMac to my 42" Panasonic 1080p TV, the connection was easy and is working fine. My questions relates to putting the iMac display to sleep when using the TV as a monitor, if I am watching You Tube, Sky Player or a DVD, I intend to use my TV as the monitor. Is it possible for the iMac to puts its display to sleep, whilst leaving the TV on. I played around with this today, however was unable to manage this.
Regards Craig

Hi Craig
There is no way to independently sleep either the iMac's Display or an attached Display/TV. However if in the Display Arrangement Preferences you set the attached Display or TV to be the Main Display and turn Mirroring Off, then FrontRow and the Full Screen Mode app's like, DVD player, QuickTimePlayer, etc. will black out the unused iMac display.
Dennis

User Contributed Tips in Intel-based iMac Your Intel-based iMac Display

*The following User Contributed Tips are located in the Intel-based iMac > Your Intel-based iMac Display forum:*
a brody - Using a second Mac as a display for a first
http://discussions.apple.com/thread.jspa?threadID=1587927
Publish date: July 7, 2008
*The following related tips are located in other areas of Apple Discussions:*
See also User Tips Library

My 20" 2.16 GHz Intel Core 2 Duo had become almost useless due to freezes and crashes- with NO crash reports in the logs.
They were often preceeded by video glitches, so I assumed it was a bad video card- unfortunately soldered to mother board.
Apparently, from forum postings, this is not an uncommon problem. The computer would run longer if the day was cooler, but rarely more than 10 minutes, so I suspected it was aggravated by heat.
Then I found this post from Bodomann on an Apple Support forum:
"Following up on my previous posting regarding my son's late model 2006 iMac that required a $900 logic board replacement:
Turns out the problem is apparently related to a bad CPU temp sensor. I installed 'iMac Fan Control' (Google it) which reported the CPU temp always at 32 degrees Fahrenheit (obviously incorrect). The same software allowed me to adjust the CPU fan manually. After multiple trials I set the CPU speed to 2800RPM after which the system would run forever - never freezing with the dreaded grey box 'reboot me' screen. I tried several times reverting the software to default speeds and the system would always crash within 10 minutes. "
I downloaded free Fan Control 1.2 for Imac from Derman Enterprises (they have an Intel iMac and a Mac Book/Pro version). It installs as a system preferences control panel. I cranked up all three fan speeds. The fans sped up noticeably. Horizontal lines have gone from screen (so far), no color artifacts and no crashes yet. I may have a real computer back! Hope Apple checks this out-
The control panel also gives the temps sensors are reporting at the CPU, hard drive and DVD drive. The CPU sensor reports the CPU temp as 32 degrees F- which is clearly wrong, unless Apple has been installing little refrigerators inside.
So thanks to Bodomann for posting- Hats off and three cheers to Derman and Cristoph for source code.
http://www.derman.com/iMac-Fan-Control
http://www.lobotomo.com/products/FanControl/index.html

When streaming a movie from an imac to apple tv, is there a way of putting the imac display off? I find it a waste having the screen on in another room. Any advice?

When streaming a movie from an imac to apple tv, is there a way of putting the imac display off? I find it a waste having the screen on in another room. Any advice?

No problem.
This is a user forum so you are not addressing Apple. There's nothing to fix, that's how home-sharing works. There would be no way for the ATV to recognize your library and display content if the computer is in sleep mode.
You can always airplay from an IOS device or use icloud if you don't wish to keep the computer on.

IMac - Display doesn´t work after restart

My iMac 21 Display doesn´t work after restart. If I turn it off and 1 hour later I want use it again the iMac shows the white screen with the mac logo and then the display goes off. I connected an external display to check if the iMac was ON and with the external display I can login and do everything but the iMac Display doesn´t work .
If I turn it off and wait 3 or 4 hours and then turn it back on the display works OK.
This is very strange behavior I have spent hours and hours trying to fine the solution or a similar issue but nothing so I am looking help here at apple.com
BTW When I bougth the iMac 21 there were some spots over the display so the display was replaced by the provider. The warranty has expired by now.

To tell you the truth, I don't know if they have to repalce the LCD panel or what they do for a bad backlight. In this reality of block or assembly replacement it probably involves repalcing the panel and not the backlight component. Don't know what it would cost. You'd have to ask that of a service center.

Why does my iMac display go off when I am starting up or waking up my machine from sleep..

Why does my iMac display go off when I am starting up or waking up my machine from sleep..?
When my iMac goes to sleep I then later try to click the magic track pad or keyboard and it will usually then show the initial password entry login screen and then go off. The machine is still on but the display is black and will sometimes flash up the screen again if I press the magic track pad or keyboard but will then black out again..

Well, there are many different reasons why it does this. It might shut off due to power voltage problems, system overheats, or there is a System Problem. The reason it might be hard to boot up is because your power button might not work properly or your system hard drive is damaged.
<Email Edited by Host>

My 27" iMac displays vertical green lines when turned on and then will not boot up

Can anyone tell me why my 27" iMac displays vertical green lines when it is turned on and then will not boot up?

Welcome to Apple Support Communities
The display or graphic card are damaged. The only thing you can do is to take your computer to an Apple Store or reseller to get your computer repaired.
If you use an external display with your Mac, connect it to your computer and see if these lines appear on the external display. If so, it's a graphic card problem

Is there any way to turn on Video Mirroring if my iMac display is FUBARed?

Okay, my iMac display is permanently frakked.
Nothing else is wrong with the system (the tech assured me, anyways). Haven't yet used Firewire Target Mode to check yet.
Regardless, I have all the proper cables and adapters--and external VGA monitor--but no way (that I know of) to turn video mirroring on.
If I can't get an external display working, I'll be out either $900 to repair the display or $3000 for a completely new system.
Ideas?

Tried it and no go.
Not sure what's wrong.
Connect the VGA cord to the Mini-DVI-to-VGA adapter
Connect to external monitor.
Boot up iMac with adapter attached. Cmd-F1. Nothing.
Boot up iMac with adapter unattached, attach after boot is finished, Cmd-F1. Nothing.
Repeat, using a different USB port for my keyboard. Nothing (x2).
Repeat again, using a third USB port for my keyboard. Nothing (x2).
If I'm not doing anything wrong**, I can only conclude the techie was incorrect and there is something else besides "just the display" that is wrong with the iMac.
**Is the monitor even connected correctly if I continuously get a "no signal" message? Or is that only because the mirroring isn't enabled?

Apples update didn't work for me: Boot Camp: iMac displays a black screen during installation of Windows 7

Boot Camp: iMac displays a black screen during installation of Windows 7 - Apple Support
I have followed each of the steps listed in the link above with no success.
Prior to adding the extra drivers I was able to start the Windows install process up to reformatting the "Windows" Bootcamp drive. After that the computer would go through some instal processes and eventually restart. After the restart the screen would go black. The black screen lead me to the Apple Support link above dated March 5 2015. After going through steps listed in the link above, I get an error message stating that the D:\Sources\instal.win. file cannot be located. I am forced to restart the computer at that point and theWindows install process attempts to start again but always ends up at the same point.
Note: I am installing windows 7 Pro from a DVD. I scanned the AutoUnattend.xml file and noticed that it refers to "Windows 7 ULTIMATE" but not "Pro" or any others that I could see. (see below). Could that be part of the issue?
Any feedback would be greatly appreciated.
<cpi:offlineImage cpi:source="wim:d:/sources/install.wim#Windows 7 ULTIMATE" xmlns:cpi="urn:schemas-microsoft-com:cpi" />
</unattend>
iMac (27-inch, Late 2009)
2.66 GHz Intel Core i5
16 GB 1067 MHz DDR3
ATI Radeon HD 4850 512 MB

Here is an over-simplified explanation of WIM and CLG files. Assume your DVD Media contains
W7- Ultimate
W7- Professional
W7- Home Premium
W7- Home Basic
WIM Files
File1
y
y
y
y
File2
y
y
y
y
File3
y
File4
y
y
File4
y
y
y
The File .wim will contains a compressed image which contains File [1...5].
The W7-Ultimate .clg will have 5 entries, with all set to 'Y'.
The W7-Professional .clg will have 5 entries, with 'Y','Y','N','Y','Y'.
The W7-Home Premium .clg will have 5 entries, with 'Y','Y','N','N','Y'.
The W7-Home Basic .clg file will have 5 entries, with 'Y','Y','N','N','N'.
This allows a single .wim Image file on the DVD media to be used to install any of the 5 flavors of Windows. When you enter your product key, the Installer knows what specific W7 variant you have the key for and will tell the WIM to extract the specific files the installer needs to be extracted.
The following line
<cpi:offlineImage cpi:source="wim:d:/sources/install.wim#Windows 7 ULTIMATE" xmlns:cpi="urn:schemas-microsoft-com:cpi" />
is telling that a retail product key will be entered, which should go look for this specific .clg file (from the five you already have on disk). You can test if it will work for you by changing this line to the following
<cpi:offlineImage cpi:source="wim:d:/sources/install.wim#Windows 7 PROFESSIONAL" xmlns:cpi="urn:schemas-microsoft-com:cpi" />
If it does not work, the other issue can be related to device discovery. Typically A: and B: device names are reserved for Floppy Drives. C: is your internal HDD.
D: can either point to the Optical drive, or the USB. The normal convention is that the removable media is named from Z: backwards. Y: and Z: are usually used for Network drives, so X: should be your USB. First try with the change to "Professional". If it does not work,

Using iMac display as extended desktop?

Hi,
is it possible at all to connect a MacBook to an iMac display to extend the desktop (or mirror)?
Thx
JP.

Hi,
yep it works with one of my laptop, but not the other one for some reasons... still working on that.
Thanks
JP.

IMac Display is jittering or subtly flickering

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