12 Replies Latest reply: Oct 4, 2010 7:57 PM by old comm guy
J & F Level 1 Level 1 (5 points)
Just noticed some strange new behavior on this PowerMac G5:

left unattended for a while, I came back to the machine running on high fan mode with black screen.
Neither mouse nor keyboard activity could to get the G5 out of this strange sleep mode, so I had to force a shut down.
Subsequent Safe Boot and Disk Utility check did not find any issues.
Energy Saver settings: set to put computer & screen to sleep after 1h (harddrive option was not selected)

Anyone have an idea what could cause this strange stand by mode?

iMac Intel Core Duo | MacBook Pro | G5 Dual | iBook G3, Mac OS X (10.5.8)
  • BDAqua Level 10 Level 10 (119,740 points)
    Most likely it shut down due to overheating.

    Have you blown the dust out of it lately?

    Get Temperature Monitor - 4.51 to see if it's heat related...

    http://www.versiontracker.com/dyn/moreinfo/macosx/19994

    And/or iStat Pro to check Fan Speeds & such...

    http://www.islayer.com/apps/istatpro/
  • old comm guy Level 4 Level 4 (2,235 points)
    Had this happen one time before I replaced the power supply in my G5. You might want to see if you can blow dust out of the power supply, as well, because it can get pretty nasty. Best way is to extract the power supply (not trivial, Google for the appropriate takeapart instructions) but you might be able to do some good blowing from front to back if you can get your air source bent around into the front fan area of the power supply.

    Suggest that in any event, you take the machine somewhere that can tolerate a lot of dust, however you blow the dust out, because as noted, it can be pretty gnarly.
  • J & F Level 1 Level 1 (5 points)
    I followed the cleaning advice and used some canned air to blow out dust,
    as far as I could reach without having the time to remove the power unit completely.

    Now the problem seems worse: the G5 will turn on, but will boot to a black display.
    I tried safe booting, still no luck. Also, the display works fine once connected to other computers.

    Running in target mode via a MacBokPro, I can see the harddrive and Disk Utility does not find any issues with the drive, but still black screen on reboot.

    Any other tricks worth trying?
  • old comm guy Level 4 Level 4 (2,235 points)
    OK, if machine boots to target disk mode, at least some things are working OK. One thing you can try (assuming you have file sharing enabled already on the machine) is to boot it up and try to connect from another machine using the finder "Go->Connect To Server" menu. If you can do that, then I would suspect the video card at this point.

    An informative try and helpful strategy is to boot into open firmware by holding down the cmd-option-O-F keys at boot. If you get a display there, then your video card is not necessarily the problem. While there if you do have video display, reset the NVRAM by issuing the command

    reset-nvram

    then issue the command

    reset-all

    and the machine should reboot. It may not help, but if you get there, then we can rule out the video card as being DOA.
  • J & F Level 1 Level 1 (5 points)
    Thanks for a very helpful lead - with the network connect, at least I know now that it's not the machine that's dying.

    So, if this is the video card, any chance I damaged or displaced while dust blowing/cleaning?
    Where exactly is the video card?
  • J & F Level 1 Level 1 (5 points)
    I just retraced the events leading up to the sudden black display:
    the G5 actually ran fine after the dust blow out operation.

    I now recall running AppleJack after the clean up, ran all tests, all was fine - then I shut down the G5 overnight.

    Now it will boot up (visible in network and via Target Disk mode), but the display will remain black.
  • old comm guy Level 4 Level 4 (2,235 points)
    Assuming you have an AGP video card (G5's before final 2005 version with PCI-express expansion), it is the bottom card in the PCI bay, that is to say, the one with the video connectors on it. That would be right below the hard drives bay.

    It is unlikely that you did anything to it by blowing dust out of the machine. Looking back at this thread, I just saw your follow-on message about the AppleJack stuff, so it did come up OK until the morning restart. The fact that safe boot doesn't give you video suggests that it is not a windowserver prefs issue, which leaves out an easy solution. The fact that it boots fully and enables file sharing really points to a problem with the video card, but there are a couple of other things we can check in the meantime that haven't been mentioned yet.

    First: how old is the backup battery? If it is more than two or three years old, it could account for some real flakiness at startup.

    Second: Have you reset the PMU? See http://support.apple.com/kb/HT1939 for PMU resets and http://support.apple.com/kb/HT1436 for SMU resets on later G5 models.

    Third: You could reseat the video card in the AGP slot, as that might restore operation.

    One other thing you could try is once again starting in single-user mode and seeing if it comes up, since that is the most barebones situation for booting and basically uses the most rudimentary Sw regime to drive the video card. Problems there and it is likely the card.
  • J & F Level 1 Level 1 (5 points)
    Thanks, old comm guy.

    Unfortunately, no luck with any of the suggested solutions:
    display not coming up after resetting the PMU, reseating the video card or in single-user mode.

    Could the video card failure have been caused by the AppleJack session
    - or did the video card just decide to go?
  • BDAqua Level 10 Level 10 (119,740 points)
    Could the video card failure have been caused by the AppleJack session...


    Extremely unlikely, I'd say a definite NO, but as time goes by I find that nothing is really impossible.
  • old comm guy Level 4 Level 4 (2,235 points)
    J & F wrote:
    Thanks, old comm guy.

    Unfortunately, no luck with any of the suggested solutions:
    display not coming up after resetting the PMU, reseating the video card or in single-user mode.

    OK, the one other area is the PRAM battery, which Apple claims can also cause this problem to occur. If the battery is more than a couple of years old, it is suspect. I would definitely try that route, as it is easy and relatively inexpensive. You can get the battery at Radio Shock but if you are near a Fry's, for instance, it's a lot cheaper there. Or you can check the open-circuit voltage with a good DVM and get a clue, the magic number being greater than 3.6 for confidence. More confidence comes with loading it with a 200 ohm resistor and measuring the voltage.

    Could the video card failure have been caused by the AppleJack session
    - or did the video card just decide to go?


    I wouldn't expect AppleJack to have had any effect on the video card. I had a 9600 Pro tank last December, which led to a succession of replacements until I finally got to where I should have been to begin with, which is the Ultra 6800. Nonetheless, do the battery thing before trying another card.

    As an aside, I started my little video card adventure by putting in a PCI video card from my G3, which did give me video but zip support for the cool stuff. That at least let me see that things were otherwise OK (I had already done the network trick, which gave me some confidence).

    These things can be an adventure, so say the least.
  • J & F Level 1 Level 1 (5 points)
    Old Comm Guy,

    finally a long overdue THANK YOU post for the tip below.

    I kept procrastinating the trip to Radio Shack, assuming the G5 tower was gone, but remembered your tip again the other day:

    bought the battery, the most expensive battery every purchased ($22), but well worth it and inexpensive in the end, since it brought the G5 back to life !!

    So, thanks again for a great tip!
  • old comm guy Level 4 Level 4 (2,235 points)
    J & F wrote:
    Old Comm Guy,

    bought the battery, the most expensive battery every purchased ($22), but well worth it and inexpensive in the end, since it brought the G5 back to life !!

    So, thanks again for a great tip!


    It doesn't always work, but surprisingly it sometimes is the exact thing needed. Glad you're back in the water!