iMac G4 Display Problems

Discussion in 'PowerPC Macs' started by cblackburn, Feb 1, 2007.

  1. cblackburn macrumors regular

    Joined:
    Jul 5, 2005
    Location:
    London, UK
    #1
    Hey all,

    I have just bought an iMac G4 1GHz USB 2.0. When I run the system for more than about 15 mins the screen dies and goes a glorious multi coloured pattern that I cannot recover from. This is persistant from then on through reboots until I Zap the PRAM.

    Any ideas on what is causing this?

    Chris
     
  2. mkrishnan Moderator emeritus

    mkrishnan

    Joined:
    Jan 9, 2004
    Location:
    Grand Rapids, MI, USA
    #2
    Mmmmm, defective hardware? But every time you zap the PRAM, it works for fifteen minutes? That's kind of weird. Try doing a more exhaustive test, out of curiosity...

    1) Zap all the non-volatile RAM using the Open Firmware method (below)
    2) Reset the PMU
    3) Run the Apple hardware test off the install/restore disc.

    But it sounds most like defective hardware (the "logic board" or motherboard).

     
  3. cblackburn thread starter macrumors regular

    Joined:
    Jul 5, 2005
    Location:
    London, UK
    #3
    Hmm, interesting second symptom I just noticed. When the system fails the air that is being blasted from the top of the case is cold, not just unhot but not warm at all.

    Surely some heat should be generated?

    Chris
     
  4. mkrishnan Moderator emeritus

    mkrishnan

    Joined:
    Jan 9, 2004
    Location:
    Grand Rapids, MI, USA
    #4
    Maybe an errant penguin has turned the inside into an igloo? :confused:
     
  5. cblackburn thread starter macrumors regular

    Joined:
    Jul 5, 2005
    Location:
    London, UK
    #5
    Ok, after some poking about with the service manual I have found what I think *might* be the problem.

    The CPU is cooled via a heat extraction pipe to the top of the case where the Heatsink is. Whenever the case is take apart the thermal seal on this heatpipe is broken and stops working.

    So my theory is that some idiot has had it apart and slapped it back together without resealing it properly. Which is bad becasue it means I have to get my hands on a Torx screwdriver set :(

    Chris
     

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