8 Replies Latest reply: Jul 18, 2013 7:48 AM by TLAMGUY
AVividLight Level 1 Level 1 (0 points)

Hey guys,


Suddenly, while lightly using my computer this morning, a bunch of strange colors and shapes appeared. After shutting my computer down (had to hold power button, because the computer froze), and restarting it, the startup screen was covered with yellow dots. After the apple logo appeared in the middle of the screen, it froze again. I shut it off, and unplugged it. After waiting a few minutes, I turned it back on, and started it in verbose mode. It seemed to work, but once I logged in, the computer ran very slowly. I shut it down using the shutdown command, and started it up again, but in AHT mode. When loading, the dots appeared, but it didn't freeze, and after it finished loading AHT mode, the dots went away. A preliminary hardware test suggests that everything is okay, but I started a test in extended testing mode, and after about twenty minutes (still testing memory), the lines came back. The extended testing hasn't completed yet, but the lines have been disappearing and reappearing at seeming random intervals.


There are five lines, about half an inch in width, and they run from top to bottom. They are a transparent yellow color, and sometimes grow/shrink.


The dots only seem to appear when the computer is first starting up, and are also transparent yellow.


This is a late 2009 27-inch iMac, with the latest os. I've had to take it in twice before, once for a broken logicboard (or, it might have been the motherboard), and once for a faulty HDD. It has all the default components, but I've upgraded the ram to 12gb.


I haven't noticed any issues leading up to this, and I wasn't doing anything very graphics intensive when it suddenly started having these issues. Also, if it makes a difference, I always shut it down at night, so it almost certainly hasn't overheated (it's not hot, anyway)



Thanks for taking the time to read this. I plan on calling a local apple store, and hopefully bringing it in to be fixed. I bought this in late 2010, so my warranty has expired, but as it has been serviced twice, I'm hoping that they'll take pity on me, and fix it one more time.


If anybody has some suggestions, or tips, for explaining this issue to the folks at apple, please let me know.



iMac, OS X Mountain Lion (10.8.3)
  • 1. Re: Five large yellow columns on screen
    Paul_31 Level 6 Level 6 (12,780 points)

    Doesn't look good - have a look at the 'More Like This' on the right >>>>>>>>>>>

  • 2. Re: Five large yellow columns on screen
    Ralph Landry1 Level 7 Level 7 (32,520 points)

    A couple months ago there were some users having similar issues, vertical lines, some wre blue, some pink, some yellow.  In each case after trying the usual, start in safe mode, etc., they took the iMacs to the Apple store genius bar and the issue turned out to be the graphics module on the logic board.  The Apple techs were successful in repairing and the iMacs worked well after that.


    If you are able, take the iMac to the genius bar and have the techs run their diagnostics, they ave far better than the AHT.

  • 3. Re: Five large yellow columns on screen
    BDAqua Level 10 Level 10 (116,480 points)



    Have you blown the dust out lately?


    Get Temperature Monitor to see if it's heat related...




    Let it cool for an hour or so, then see if you can do this...


    Take a screen shot & view that in Preview, move the Preview window around, if you see double lines it's a Video card/VRAM problem, if the lines do not move moving the pic around then it's the LCD or cable.

  • 4. Re: Five large yellow columns on screen
    AVividLight Level 1 Level 1 (0 points)

    No, I haven't blown the dust out lately (or ever, for that matter), how would you suggest I do that? Will I have to take the back off?

  • 5. Re: Five large yellow columns on screen
    AVividLight Level 1 Level 1 (0 points)

    Sorry for making two replays, I couldn't find an edit button.


    I can get my computer to get past the start up screen, as yellow dots appear, and it freezes.

    Thanks for your help, though

  • 6. Re: Five large yellow columns on screen
    BDAqua Level 10 Level 10 (116,480 points)

    Opening is the best way, but not easy on many, at least blow out the top cooling slot that rin the length of the top, open the RAM slot & blow that out, & then the little fan intake grill in the lower back behind the stand.

  • 7. Re: Five large yellow columns on screen
    TLAMGUY Level 1 Level 1 (0 points)

    I also have a late late 2009 27-inch iMac with very similer display issues.  I tried all the reset options and even set up an external drive with OSX to verify it wasn't a software issue.  Bottom line is that I spent about 2 weeks on all that and got nowhere.  I did learn a lot about Safe Mode, SMC, PRAM, VRAM, etc, etc.


    That said, I finally took it to an authorized Apple Repair shop and they are replacing my video card.  AHT was unable to diagnose the card as defective but their local diagnostic tools did.  They are also going to clean out the interior as part of the service.  That way you can be sure to get your display and glass back together without smudges or prints.


    I would recommend just taking it in and getting it fixed.  In my case, this should get me back online with my iMac pending the next tech refresh for the rMBP.  If the new rMBP will meet all my needs, I'll use the iMAC as a monitor until it no longer works then just get another thunderbolt compatible monitor.

  • 8. Re: Five large yellow columns on screen
    TLAMGUY Level 1 Level 1 (0 points)

    iMac is back and video card replaced.  Works like a champ.  Total cost was about 42,000 yen (420 US).