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Diagnosing video problem

374 Views 4 Replies Latest reply: Aug 22, 2013 8:52 PM by Swampus RSS
aronfromtoledo Calculating status...
Currently Being Moderated
Aug 14, 2013 12:08 PM

Hi all,


I've got a PowerMac G5 2.0 GHz from May, 2004. It has the original ATI Radeon 9800 Pro graphics card. I recently had to replace the logic board (with a working used one). That worked fine for months, but now I'm getting video problems. I'll get flashing vertical stripes of short horizontal bars. Sometimes it seems that if I jiggle the display connector at the computer, the screen settles down for a while, but it is not completely certain that this is cause and effect. I hooked up a TV to the DVI port (using Apple's DVI-Video adaptor) and got the same issues, so it's not the display or the cable. I'm hoping that it's a graphics card problem, and not the "new" logic board. Is there a troubleshooting procedure, short of buying and trying a new graphics card, that would let me narrow down the problem?


Thanks for any help.



PowerMac, Mac OS X (10.5.8), original PowerMac G5 2.0 GHz dual
  • Swampus Level 2 Level 2 (180 points)
    Currently Being Moderated
    Aug 14, 2013 8:16 PM (in response to aronfromtoledo)

    What you describe sounds like a failing graphics card.  My particular troubleshooting process is to swap in another one to see if it works.  It's handy to have a few extra parts.  Short of that, you might try downloading ATIccelerator and using it to downclock the card.  Downclock both the GPU and memory by 5 to 10%.  If it helps, that would give a more clear indication.



    Also, if downclocking helps, it might still be possible to salvage the card.  As with virtually everything else, Japamac has a nice tutorial on the subject of card maintenance:


    First read his overview: CA431.html


    Then read the teardown instructions for your specific card: 65BB5.html


    Applying fresh thermal compound is not an optional step.  Maybe wait to see what others have to say about this suggestion before purchasing the compound.  The fact that it isn't doing it all of the time leads me to believe that it might not be too late, but I don't know how common it is to bring them back once they start showing problems. 


    Before anything, I might try reseating the card and not just wiggling it from the outside.  Take it out, blow out the dust with some compressed air, and verify that the fan moves freely.  Clean the contacts on the card with a pencil eraser.  Also verify that the fan is actually working when you put it back in.


    There might be something else obvious to try that totally eludes me at the moment.  Hopefully, you'll get some better feedback than this.  Good luck.

  • BDAqua Level 10 Level 10 (114,705 points)
    Currently Being Moderated
    Aug 19, 2013 9:29 PM (in response to aronfromtoledo)

    Sounds like the PSU or the front button swith, can you test voltages?


    Here's some more info on G5 PSU voltage values:

  • Swampus Level 2 Level 2 (180 points)
    Currently Being Moderated
    Aug 22, 2013 8:52 PM (in response to aronfromtoledo)

    What a bummer!  Have you had a chance to test the PSU yet?


    If this is a machine that you'd like to keep going a while longer, I'd keep an eye out for a working parts machine.  In my area, working dual 2GHz models can be picked up for $100.  That would give you an extra PSU, motherboard, CPUs, video card, and extra ram that you can start using right away.  It takes the guesswork out of troubleshooting when you can swap in known good parts.


    Please keep us posted.


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