Squares/lines on screen – is my GPU failing? (Late 2009 27" iMac)

Discussion in 'iMac' started by nickwalters, Aug 28, 2015.

  1. nickwalters, Aug 28, 2015
    Last edited: Aug 28, 2015

    nickwalters macrumors newbie

    Joined:
    May 11, 2011
    #1
    Hi,

    A few months back there were very faint vertical lines on my late 2009 27" iMac. They were only particularly noticeable when editing photos or looking at the screen very closely. A few months back I opened up the iMac, removed lots of dust which I think was causing over-heating and did a fresh install of OS X. The lines seemed to occur less frequently and I hadn't had any issue since, until today.

    Today my iMac suddenly froze whilst I was repairing disk permissions. The screen was covered in bizarre white squares. The mouse moved, but otherwise the entire system was unresponsive, including force-quit not working. This was the first time this type of thing happened.

    After attempting several hard reboots, black vertical lines appeared on the startup screen and the system would not boot (it got stuck on a dull grey-white screen after the Apple logo had disappeared and the lines remained). I attempted PRAM and SMC resets and booting in safe mode but none of these worked. I then attempted to enter recovery mode, which didn't happen, but the system instead booted and there were no issues with the graphics.

    After 10–20 minutes of using the iMac as normal, the same happened again, except that the squares contained lines of multiple colours. I attempted PRAM and SMC resets, which didn't help. I then repaired the disk and disk permissions in recovery mode. Still it wouldn't boot. I then managed to boot in safe mode but this time the lines (now more like thick bands of vertical grey lines, evenly spaced across the screen) persisted. After reaching a certain point at startup, the bands gained an extra blue line in the centre, 1px thick. Having restarted again, the bands are now completely 'noisy' and multicoloured.

    EDIT: I just noticed that by simply selecting an area on the desktop, these bands disappeared. I was able to remove them all by dragging over them. I then restarted and again the system froze as usual after the Apple logo disappeared. It seems that I can only boot in safe mode.

    I have read that this could be a CPU issue but is most likely a GPU issue. I have also read that (at least in laptops) the CPU and GPU are built into the logic board and I know that iMacs use some laptop components – is the GPU built into the logic board in this iMac model? If so, should I risk assuming that the GPU is the cause of failure and replace the logic board? Are there any other possible causes of this problem?

    I want to avoid having to have this repaired professionally. Is there any soldering involved or is this something I could do myself? I no longer live in the country where I purchased it (Sweden) and there are no Apple stores (only resellers) where I live now (Finland). It's obviously not covered by a warranty.

    Thanks for any advice!
     
  2. sebastius macrumors newbie

    Joined:
    Feb 22, 2015
    #2
    The GPU can temporarily be fixed by reflow-soldering with a hot-air soldering-tool. It is a temp-fix, it will fail again in two days to two years. Impossible to predict.

    If you can't find someone in your country who can do that (shouldnt be a problem), you can ship it to me in the Netherlands, i do a lot of these boards (and other boardrepairwork).
     
  3. Significant1 macrumors 6502

    Joined:
    Dec 20, 2014
    #3
  4. nickwalters thread starter macrumors newbie

    Joined:
    May 11, 2011
    #4
    Thanks for the tip. I would rather replace the GPU if possible, rather than spend money on a repair that might not last.
     
  5. nickwalters thread starter macrumors newbie

    Joined:
    May 11, 2011
    #5
    Thanks very much for the advice. I can't find any Mac versions of the 4850 or 5750 online (the PC versions look quite different, more like a card with a fan than a self-contained component with a heat-sink). Do you know where I would be able to get one? I live in the EU but am visiting the US next week so could buy from there as well. I don't need anything fancy, I don't do video editing or gaming, just photo editing.
     
  6. Significant1 macrumors 6502

    Joined:
    Dec 20, 2014
    #6
    I also live in EU and got mine from a local technician. Apple is very strict with spareparts. When ordering a new from Apple, they will have to send the old one back. Not in my case though, because he happened to have this second hand card.

    The graphics adapter used in iMac are mobile versions (MXM format) and you can find them on ebay. The one for pc's are a lot cheaper, but will not work without a reflash. The technician I got my card from, was himself curious if it could be done. Most are from US.
    http://www.ebay.co.uk/sch/i.html?_o...adeon+hd.TRS0&_nkw=imac+27+radeon+hd&_sacat=0
    The most powerfull you can get is the 6970, but it is very expensive, especially the 2GB variant. Also it has a bad history, where Apple acknowledged there was a widespread problem and made a replacement program, so I would not recommend it.

    I hope my 5750 will last for the rest of the life of my iMac. Performance is not much better than 4850, but more fluid and it is a lot cooler. It also handle mission control animations better (not perfect) due to the 1GB vram.
     
  7. nickwalters thread starter macrumors newbie

    Joined:
    May 11, 2011
    #7
    Thanks, I didn't realise it's so difficult to get parts directly. I have contacted a couple of local Mac certified resellers/repairers for quotes. Hopefully I can get a 5750 as my system gets extremely hot. I know the body acts as a heat-sink but still, it can't be good for the other internal components...
     
  8. mtbdudex macrumors 68000

    mtbdudex

    Joined:
    Aug 28, 2007
    Location:
    SE Michigan
    #8
    What did you end up doing here?
    My late 2009 27" iMac is doing same thing.
     
  9. nickwalters thread starter macrumors newbie

    Joined:
    May 11, 2011
    #9
    Hi, sorry for the slow response. I actually got away with opening up the iMac, giving it a very thorough clean to remove all the dust inside and replacing the thermal paste, which had dried out and was failing to carry the heat away from the GPU. I haven't been using it much myself since – I think there may still be a few faint lines that were there before this major problem – but my wife's been using it very intensively for photo editing and we use it as a TV everyday, and it's been fine for over a year.
     
  10. macmee Suspended

    macmee

    Joined:
    Dec 13, 2008
    Location:
    Canada
    #10
    my 2010 imac had these little boxes on the screen too. I sat far enough back so that I did not notice them unless I was up close looking directly for them!
     
  11. mtbdudex macrumors 68000

    mtbdudex

    Joined:
    Aug 28, 2007
    Location:
    SE Michigan
    #11
    I'm taking the hard drive out, trashing it, then throwing the old girl out.
    She's sat for 8 months now unused ....
     

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