iMac display troubles after HD replacement -- need help

Discussion in 'iMac' started by Darjeeling, Jan 31, 2010.

  1. Darjeeling macrumors newbie

    Sep 27, 2009
    [UPDATE: issue now fixed. If you're upgrading the iMac HD, pay particular attention to the LCD ribbon cable -- mine apparently came loose with little jostling during the drive upgrade]

    Hey all. I'm looking for some advice with a self-inflicted H/W problem. (Hi, Jamie!)

    Using HD replacement guides referenced elsewhere in the forums (, I swapped out the 320GB original in my mid-2007 20" Alu iMac for a 1.5TB Barracuda. I had no obvious problems -- thought everything went fine, though the internals of my machine are somewhat different from those shown in the 2 guides -- but it was completely dead when I plugged it in and tried to start it. Opened it up again, rechecked all connections -- it started, but with horrible video artifacts (lots of snow, etc.).

    I powered it down and opened it up a third time, completely unplugging and reseating all connections. Although I did not originally untape or unplug the big ribbon cable at the top of the LCD panel, this time I checked this connector and pushed on it a bit to check for a tight fit.

    This time it booted off a CCC clone on an ext drive (I cloned back to the new int drive). BUT... I still have video artifacts -- primarily involving reds (see the pics below). For example, certain colors on the MacRumors front page that should be uniform are now banded vertically and I'm seeing horizontal lines across areas of uniform color (such as menu bars and window frames and the pictured snip from an Apple Support page). Look carefully at the snap from the iPad story; you should also see red banding in the black frame of the iPad.

    This may be related or not, but I'm also getting KPs at startup (no external drives attached). I upgraded from 2 to 4 GB the night before without any troubles prior to the HD swap (I restarted the machine several times immediately after the RAM upgrade to change startup drives, etc. -- no problems). I'm about to remove and reseat the RAM and see if that resolves the KP issue. [UPDATE: clean reboot after reseating the RAM. Teh snappy seems to be back.]

    ADDITIONAL: I also replaced the clock battery while the chassis was open. Over the last year or so, the iMac would sometimes forget speaker volume and monitor brightness settings at reboot - both going to max volume/brightness. Couldn't hurt to replace it, right?

    Before I open up the beast one more time, any suggestions on what I should look to fix in my botched HD upgrade?

    Attached Files:

  2. Darjeeling thread starter macrumors newbie

    Sep 27, 2009
    The PNGs look normal on my work computer

    Weird, the PNG screenshots I attached look 110% normal on my office monitor -- no artifacts whatsoever. This rig has a decent HP LCD monitor running at 32-bit resolution (Windoze).

    Do other folks see the red lines and/or shading in the screenshots?
  3. archipellago macrumors 65816

    Aug 16, 2008
  4. Darjeeling thread starter macrumors newbie

    Sep 27, 2009
    Thanks archipellago

    OK, so no artifacts on other displays -- thanks archipellago. The artifacts I saw on the iMac were faithfully reproduced in the screen shots -- no changes to their appearance as I moved the PNGs around the screen. So not a "local" effect on one part of the LCD versus another.

    Then can I safely assume that the video card output is ok? I'm beginning to think I need to check the big ribbon connector on the back of the LCD once again...

    Just found this HD swap guide, which suggests the ribbon cable might be the issue --->
  5. Robbbin macrumors newbie

    Feb 25, 2009
    That's because you took screenshots, this tells us that there is nothing wrong with image rendering on your videocard. On the other hand, it seems like the screen has been damaged during the HD-swap. One you can also try is to attach an external monitor to it, see if it has the same problem. If it shows a fine picture, then the problem is not in your videocard.

    Have you tried a clean install?
  6. Darjeeling thread starter macrumors newbie

    Sep 27, 2009
    FIXED -- I think it was the ribbon cable

    Thanks for the responses.

    Disassembly #4 did the trick. I disconnected and then reconnected the ribbon cable near the top of the LCD panel, taping it down for good measure -- and the display is back to its pre-HD replacement glory (well, as glorious as this fake-IPS, 6-bit panel is gonna get).

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