Help! iMac G5 with purple squares

Discussion in 'PowerPC Macs' started by sk8almost44, Jul 28, 2016.

  1. sk8almost44 macrumors newbie

    Joined:
    Jul 28, 2016
    #1
    Can someone please help me fix this issue. It starts up and after 5 minutes purple squares pop up and move. I have attached a picture. Thank you so much.

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    --- Post Merged, Jul 28, 2016 ---
    [​IMG]
     
  2. iModFrenzy macrumors 6502a

    iModFrenzy

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    #2
    Artifacts could mean it's overheating, I'm no expert at this though. Check the temps. I usually keep track of my temps with iStat Menu (shows the usage/CPU temp).
     
  3. lcdswat macrumors newbie

    lcdswat

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    #3
    I think that the problem occurs due to overheating. It's an old computer, and most likely no one cleaned it from dust. I would start with that. Unfortunately, the video chip can be damaged or lose touch with the board, but you need to hope for the best and to start just everything clean.
     
  4. Altemose macrumors G3

    Altemose

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    #4
    This is sometimes attributed to capacitors blowing. The GPU sometimes begins to fail before the rest of the machine fails to power on. While overheating can definitely attribute to this sort of problem, artifacting is caused by solder joints starting to loosen and break. Sadly, Apple has had its fair share of GPU and capacitor issues, with primarily capacitor issues in the iMac G5 line.
     
  5. Daniël Oosterhuis macrumors 6502a

    Daniël Oosterhuis

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    #5
    Take the back off and take a few pictures, and post those here. Simply put the iMac screen side down on a table, preferably with a cloth on it to prevent scratching/scuffing, and unscrew the 3 screws underneath the Mac. These will not come out, as they're meant to stay in place for convenience. Then you can slide the back off. If you see any bulging capacitors, and especially capacitors with brown goo-ish stuff coming out, well, than that's the problem.
     
  6. sk8almost44 thread starter macrumors newbie

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    Jul 28, 2016
    #6
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    --- Post Merged, Jul 30, 2016 ---
    I cleaned it completely before I ever turned it on to check it out. I don't see any blown capacitors. Over heating, as in both fans aren't running?
     
  7. Xandros macrumors regular

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    Sep 19, 2010
    #7
    http://www.playtool.com/pages/artifacts/artifacts.html

    If that's anything to go by then that odd screen artifact issue you're experiencing is apparently being caused by bad video RAM. You need to replace the graphics card... Which on these iMac's means you need to replace the whole logic board.
     
  8. sk8almost44, Jul 30, 2016
    Last edited: Jul 30, 2016

    sk8almost44 thread starter macrumors newbie

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    Jul 28, 2016
    #8
    Sometimes it happens immediately, sometimes it happens after 10-15 minutes of playing around on it. It is not hot to the touch, the fans re running, it's clean inside and out, there are no blown or leaking/bulging capacitors, i don't know why it keeps doing this. I have posted a video below. When it does this i am unable to do anything and it freezes like this.

     
  9. Orizence macrumors 6502

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    Nov 10, 2014
    #9
    It might just be a dead GPU unfortunately
     
  10. Xandros macrumors regular

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    Sep 19, 2010
    #10
    I refer you to what I already wrote in post #7 above yours. Unfortunately it doesn't really matter if you've cleaned it inside and out, or if you've inspected the components and haven't found anything untoward, or how long it takes for the issue to occur: The damage has evidently already been done, and it is for all intents and purposes irreversible. The GPU is toast, and since the GPU is soldered onto the logic board, you need a new logic board.
     
  11. Daniël Oosterhuis macrumors 6502a

    Daniël Oosterhuis

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    #11
    Yep, the caps look too clean to be at fault. Caps can fail without too much visibility, but in these iMacs, they always pop. Sadly, this Mac is better left as a parts unit, since a new logic board will most likely end up costing more than just a different iMac G5.
     
  12. Altemose macrumors G3

    Altemose

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    #12
    Some people have great luck with removing the logic board and reflowing it by baking it in the oven. It is a very home brew repair, but it does yield great results. @bunnspecial has done it with a 2008 MacBook Pro, and I personally have tried it on an HP Pavilion with great success.
     
  13. 128keaton macrumors 68020

    128keaton

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    Jan 13, 2013
    #13
    Stuff I have successfully reflowed:

    * 2008 iMac GPU
    * Nvidia 8800GS
    * 2010 Macbook Pro
    * Another 2010 MacBook Pro
    * Same iMac GPU (bought another GPU a bit later)
     
  14. MagicBoy macrumors 68040

    MagicBoy

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    #14
    That's typical of a failed AMD GPU and/or VRAM.
     
  15. Orizence macrumors 6502

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    Nov 10, 2014
    #15
    Unfortunately sticking a card in the oven doesn't actually fix it. It will work again, but its not fixed; it will die again
     
  16. 128keaton macrumors 68020

    128keaton

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    Jan 13, 2013
    #16
    The iMac listed above lasted for TWO years. As long as you repaste it properly, it shouldn't be a problem. Plus, that gives OP time to save for a new Logic Board
     
  17. Orizence macrumors 6502

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    Nov 10, 2014
    #17
    Im aware in some cases it can work for a long time, but its not really fixed. Its not the solder thats the issue, its almost always the underfill in earlier revisions of a chip, for example the Nvidia chips that were used in the 08 MBP had a later revision that weren't defective; but if I remember correctly they weren't used in any of the MBPs
    --- Post Merged, Aug 1, 2016 ---
    I have nothing against repairs like that, but its not really fixing it. Also its not reflowing the solder, sticking a heathen for a few minutes over the chip will do the same thing, very rarely do people actually let the solder get hot enough to melt.

    Not the greatest article on these issues, but better than some of them that I read: http://www.theinquirer.net/inquirer/news/1004378/why-nvidia-chips-defective
     
  18. Xandros macrumors regular

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    Sep 19, 2010
    #18
    Well at this point he's not really got anything to lose. Worst case scenario is a reflow ****s it even more or doesn't do anything to fix it but he would need a new logic board anyway, so no difference. Best case scenario the reflow un****s it and it works for another few weeks/months/years.
     
  19. Orizence macrumors 6502

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    Nov 10, 2014
  20. didius macrumors newbie

    didius

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    Jun 6, 2015
    #20
    There seem to be three caps missing? My iMac G5 had caps on these spots?
     
  21. MacCubed macrumors 68000

    MacCubed

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    Florida
    #21
    Though it appears that they are missing, they are infact not supposed to be there. It does look kind of weird looking at it now, but that's how Apple designed it.
     
  22. MagicBoy, Aug 4, 2016
    Last edited: Aug 4, 2016

    MagicBoy macrumors 68040

    MagicBoy

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    Location:
    Manchester, UK
    #22
    It's likely power circuitry for something not implemented on that model of iMac. There's also a couple of MOSFETs and an inductor "missing".

    Cheaper to make one design of logic board than a specific one for say different models with a variation of CPU/GPU.
     

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