Faulty iMac - screen 'roller blind effect' then lock up :-(

Discussion in 'Mac Basics and Help' started by PedroDiniz, Mar 26, 2009.

  1. PedroDiniz macrumors newbie

    Jun 6, 2005

    My Dad is having some problems with his iMac. Specs as below:

    Model Name: iMac
    Model Identifier: iMac6,1
    Processor Name: Intel Core 2 Duo
    Processor Speed: 2.16 GHz
    Number Of Processors: 1
    Total Number Of Cores: 2
    L2 Cache (per processor): 4 MB
    Memory: 1 GB
    Bus Speed: 667 MHz
    Boot ROM Version: IM61.0093.B07
    SMC Version: 1.10f2
    Serial Number: W863702QVGN

    NVIDIA GeForce 7300 GT:

    Chipset Model: NVIDIA GeForce 7300 GT
    Type: Display
    Bus: PCIe
    PCIe Lane Width: x16
    VRAM (Total): 128 MB
    Vendor: NVIDIA (0x10de)
    Device ID: 0x0395
    Revision ID: 0x00a1
    ROM Revision: 3021
    Display Type: LCD
    Resolution: 1920 x 1200
    Depth: 32-bit Color
    Built-In: Yes
    Core Image: Hardware Accelerated
    Main Display: Yes
    Mirror: Off
    Online: Yes
    Quartz Extreme: Supported
    Display Connector:
    Status: No display connected

    When he is using the internet he is experiencing some bizarre things!
    The screen begins to get dark, starting at the top of the screen and moving down the screen like a roller blind, until the whole screen has darkened - you can still see the desktop image underneath - its a bit like when you select the Dashboard, only darker. Then a message pops up, much brighter than the darkened background. The message says,

    "You need to restart your computer. Hold down the power button for several seconds or press the Restart button"

    The rest of the message box is obscured by what I would describe as colourful TV interference. Like an untuned TV picture.

    If left, the iMac goes to sleep, but won't awaken. It just locks up. The usual sleep LED on the front of the mac, which usually blinks, is not lit up at all.

    I've attached a screen shot to show what I mean. The actual screen is darker than it looks in this image - I think the flash has caused it to look brighter here, but hopefully you get the idea! Cheers.

    Any ideas VERY welcome please!! :)

    Thanks in anticipation.

    PS: apparently this doesn't happen at all if my Dad is not using the internet at the time, and it also started after he had posted up a message on a boat classified ad website.

    Attached Files:

  2. Jethryn Freyman macrumors 68020

    Jethryn Freyman

    Aug 9, 2007
    That's called a kernel panic. Could be a hardware issue, run the Apple Hardware Test.
  3. Makosuke macrumors 603

    Aug 15, 2001
    The Cool Part of CA, USA
    Normally kernel panics (hard crashes--Mac equivalent of a bluescreen or the old-school bomb) are caused by either an external hardware conflict (bad USB device or something), bad low-level software (a driver or system hack you installed), a corrupt MacOS install (rare but possible), or a physical problem with the Mac's hardware.

    The fact that the panic message is garbled makes me think it's one of the last two; something's chewing it up before display, making me think it's either a hardware problem or corrupt OS install. Running the hardware test disc that came with the computer, as Jethryn Freyman suggested, will hopefully tell you if it's a hardware problem. If that comes up clean and you haven't installed any low-ish level software (like a hack or driver) then try unhooking anything not vital to using the Mac. If it still reoccurs, then try an OS "archive and install"--time consuming, but will probably fix it.
  4. BlueRevolution macrumors 603


    Jul 26, 2004
    Montreal, QC
    Yeah, I've never seen the kernel panic message look garbled like that...
  5. PedroDiniz thread starter macrumors newbie

    Jun 6, 2005

    Hey, thanks for all the advice :D I'll call my Dad tomorrow and let him know what you folk suggest and let you know how I get on.

    Thanks again, much appreciated!

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