iMac G5 - forcing external video output

Discussion in 'PowerPC Macs' started by NeverhadaPC, Apr 12, 2009.

  1. NeverhadaPC macrumors 6502


    Oct 3, 2008
    My wife's 20" iMac G5 (no iSight) worked GREAT for 3 years. Then the warranty expired and three months later: Display failed. That is, after turning on the computer we would hear normal start-up sounds, we could change the volume via the keyboard, but the screen was black.

    After looking here and elsewhere we first assumed:
    1. Logic board. This was not the case as we went to Apple store and by resetting PRAM we were back up and running... for 2 days, then black screen once more.
    2. Video-card. We went back to the store and the iMac was connected to external display which quickly displayed our video-output. The preferences had been changed to "external display" (don't know how). A Genius installed an earlier version of OS X Tiger and once again we were back up and running. We went home, re-installed updates for Tiger and the next day, after a sleep-cycle, the computer had changed the preference files to external display again. Black screen.

    Has anyone experienced this before? Did upgrading to OS 10.5 (a 100 dollars cost) solve this problem? Any advice?
  2. iLog.Genius macrumors 601


    Feb 24, 2009
    Toronto, Ontario
    So your iMac's display will go black when connected to an external display? I'm a bit confused as what the problem is. Could you clarify, sorry.
  3. NeverhadaPC thread starter macrumors 6502


    Oct 3, 2008
    Sorry for the confusion... trying to make a long story too short, I guess.

    The problem is that every time we boot up or restart the computer there will be no video output to the LCD on the iMac (black screen) but the computer is ON (since the keypad "Volume Up" key on the iMac gives off sounds).

    However, if I attach an external monitor to the iMac then video will be output on the external display but via preferences I can set the "video output" back to the iMac - major hassle and I don't have a decent monitor so this is not a solution.

    The problem is the Preference files forcing the iMac to output to external display, even when none is used/plugged in. When the Apple "Genius" re-installed OS X 10.4 on the iMac the problem disappeared, but then after downloading the updates for OS 10.4 - whoopti doo - the problem returned... makes more sense?

    Not sure if any one has had this problem with iMac G5 (no iSight)? Not sure how to fix it since the newest update from Apple seems to be causing the problem. I could update to OS X 10.5 but it costs 100+ dollars so I would rather have evidence that an upgrade will indeed fix the problem.

    Makes sense?

  4. NeverhadaPC thread starter macrumors 6502


    Oct 3, 2008
    So the answer to your question is: no. Connecting an external display works and gives me the iMac's video output as it should. The problem is that every time I restart the computer, the iMac "thinks" that an external display is hooked up, causing it to go to black screen...
  5. California macrumors 68040


    Aug 21, 2004
    I have that same 20" 2.0ghz iMac G5 that the warranty also just ran out on but no problems at all on Tiger.

    if you still have your OEM system discs, I would do a fresh install.

    After three years, btw, your hard drive is in need of replacement and you should max out the ram while you are at it. It is VERY EASY TO DO.

    These iMacs run best on paired 1 gig sticks. Could be a good time to do the fresh install with your OEM OS, (is yours tiger or panther?)

    Do the OEM OSX discs re install first. The Tiger updates have killed many a PPC machine, I would avoid them. I think my OEM discs are Tiger? Can't recall. Anyway, do the re install and DON'T DOWNLOAD THE UPDATES.
  6. NeverhadaPC thread starter macrumors 6502


    Oct 3, 2008

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