iMac G5 multiple issues. For the advanced between us.

Discussion in 'PowerPC Macs' started by iDutchman, Feb 7, 2012.

  1. iDutchman macrumors 6502a

    May 9, 2010
    Amsterdam, NL

    My iMac G5 1,8Ghz appears to have some very weird problems.
    First, when I press the power button it will give the sound and eventually turn on the screen. It will boot but after 10 seconds, it turns off. So it still turns off at the boot screen with the logo!
    After a PRAM reset (1x), no luck.

    BUT, after a PRAM reset (wait for the 3rd restart) it boots!

    It boots into Tiger (new 2TB HD, fresh install). But, it shows these lines real bad as if the graphics card is failing. Also, this fades away until is normal!
    When doing a screenshot, is shows no lines. Perfect screenshot.

    At a reboot, it boots without doing anything.

    But when it is off for a while, same problem persists.

    What can be wrong?


    - Boots after 'all hardware reset --> alt+cmd+p+r till 3rd reboot"
    - New 2TB HD (old one crashed)
    - Weird Graphics card like issue at boot (when it boots)
    - Issue fades away till normal behavior
    - Screenshot shows no interferences.

    See pictures for further details! Screenshot was taken when heavy screen distortion occurred.

    Attached Files:

  2. robla64 macrumors newbie

    Jan 4, 2007
    Have you inspected the capacitors on the motherboard? There are quite a few and are know to leak/blow.
    I have fixed a few dead G5 iMacs by replacing the caps. Unfortunately, it requires removing the logic board.
    Take another picture with the back off and we can tell you for sure.
  3. iDutchman thread starter macrumors 6502a

    May 9, 2010
    Amsterdam, NL
    I did. But I made some pictures. I don't see anything out of the ordinary?

    There are also 2 places where there are only 2 capacitors, they are fine.

    Attached Files:

  4. Macman756 macrumors 6502a


    Sep 24, 2008
    Atlanta, GA
    It's possible those capacitors have just started to leak, and not bulged yet. Or just failed or leaked from the bottom. I've seen many different cases, all surrounding those caps. It is possible it is a bad graphics chip, cold solder joint etc. A new logic board would more than likely fix the issue. It's probably either caps or GPU.
  5. iDutchman, Feb 8, 2012
    Last edited: Feb 8, 2012

    iDutchman thread starter macrumors 6502a

    May 9, 2010
    Amsterdam, NL
    The weird thing is, that when performed a PRAM reset it works flawlessly (with the little distortion in the first minute).

    I ran all evening in the kitchen wirelessly streamin music to the Airport Express of Spotify (via Airfoil). I put it into sleep mode, and that works.

    I come back the next morning, and the same problem persists. Could it have anything to do with the PRAM battery? I'll be picking up a defective identical iMac G5 in half a hour for 15 euro's. Maybe it can gut some parts of mine onto that one if that makes one fully working machine. . ;)
  6. iDutchman thread starter macrumors 6502a

    May 9, 2010
    Amsterdam, NL
    as it turned out. The other iMac G5 I picked up, appears to be a 17".

    17" w/ bluetooth, Airport Extreme card, 1.5GB RAM, 320GB.
    The PSU of it was dead, so this got replaced (I work at the Apple Store) and we still have stuff like that lying around.

    This, now, is fully functional for 15 euro's.

    But, this does not solve my 20" issue. It works when it's on. Fully!..
  7. SimonUK5 macrumors 6502

    Nov 26, 2010
    If you work at the Apple Store, can you not get a New G5 20'' Logic board for free/cheap? :)

    but for 15 euros that an awesome machine :)
  8. skinniezinho macrumors 65816

    Jan 1, 2009
    Even if he does it must pay for it and they aren't cheap.
    Why don't you run aht on that computer?
  9. burnout8488 macrumors 6502a

    May 8, 2011
    Endwell, NY
    The GPU is most likely the problem.

    The tiny solder joints holding it to the board sometimes break, causing lines on the screen.

    If you cover your logic board in tin foil, only exposing the GPU, then bake it in an oven (recommended temps and times are on the 'net), it will re-flow the solder and should fix the problem.

    That is, as long as all of your capacitors are good.
  10. iDutchman thread starter macrumors 6502a

    May 9, 2010
    Amsterdam, NL
    I traded the 20" iMac for another 20" iMac (ALS/2.0Ghz model) with only a dead PSU. I also got 25 euro's extra. Good deal! It will fully function with a new used PSU. This thread can be closed.

    Thanks everyone.

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