Old Mac Fan Whirring Won't Boot Up

Discussion in 'PowerPC Macs' started by Gooz, Aug 10, 2014.

  1. Gooz macrumors newbie

    Joined:
    Aug 10, 2014
    #1
    Hi All

    I've got an old G4/G5...can't remember which it is. I'll add at this point, I'm not very technical when it comes to computers. It's a tower anyway.

    I went to turn it on the other day and it worked first go. However, I forgot the name and password so tried to boot form the installation cd. Since then the fan is whirring loudly, and it's not booting up. This had happened before, and I cannot remember if/how I solved it. I removed the cd, but the problem remains.

    I have read about opening the mac and cleaning dust out. I tried. I unscrewed parts of the mac, but could not see a way to easily dismantle it.

    The point is, it's an old mac, and if this is a sign, it's dying/dead, I'm happy to let it go. I was just hoping to wipe it before I get rid OR salvage it maybe for extra storage space if it did work.

    Is it worth trying a bit harder OR am I fighting an eventual losing battle? :) What would my next move be if trying to salvage it?

    Any advice appreciated. Thanks :)

    G
     
  2. Macman45 macrumors demi-god

    Macman45

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    Jul 29, 2011
    Location:
    Somewhere Back In The Long Ago
    #2

    Do you get any image on screen?
     
  3. Gooz thread starter macrumors newbie

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    Aug 10, 2014
  4. Gooz thread starter macrumors newbie

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    Aug 10, 2014
    #4
    Nothing! Blank! :(
     
  5. Macman45 macrumors demi-god

    Macman45

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    Jul 29, 2011
    Location:
    Somewhere Back In The Long Ago
    #5
    Lolls like the GPU has died. Or the screen. If you get nothing at all then maybe a test with another screen ( it's a tower right?) could be the next test. Without any visible activity screen wise it's hard to diagnose further
     
  6. Altemose macrumors G3

    Altemose

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    Mar 26, 2013
    Location:
    Elkton, Maryland
    #6

    Try doing a PMU reset.
     
  7. Gooz thread starter macrumors newbie

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    Aug 10, 2014
    #7
    Thanks! The screen definitely worked only a couple of days ago. When I attempted to boot it initially the computer started and so did screen. But next time when it started the whirring started and the screen was blank. Can I ask what a GPU is?

    ----------

    Sorry what's a PMU? I'm not very technical!:)
     
  8. bunnspecial macrumors 603

    bunnspecial

    Joined:
    May 3, 2014
    Location:
    Kentucky
    #8
    PMU is short for power management unit. It's reset by pressing a small black button on the logic board.

    The exact procedure on how to access the logic board is going to depend on whether you have a G4 or a G5 tower. They're very easy to tell apart-the G4 is all plastic on the outside, and the G5 is all aluminum with a "cheesegrater" front.

    On the G4s, look for a plastic tab in the side panel on the right hand side(with the front of the computer facing you). Lift this up, and the entire side panel should then hinge down. The logic board is attached to the side panel. Look for the battery, and then look for a small black button next to it. Push it once, and only once, then try rebooting.

    On the G5s, the side panel is removed by lifting up a large lever on the back(you can't miss it). The side panel will then hinge down from the top, and can be lifted up and away from the computer. Once this has been removed, there is a clear plastic air deflector that you need to remove-this just lifts up and out. The PMU reset is located on the bottom of the logic board, just in front of the fan and below the memory.
     
  9. Gooz thread starter macrumors newbie

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    Aug 10, 2014
    #9
    Thanks, I'll try that! (It's a G5 by the way.)

    G
     
  10. Altemose macrumors G3

    Altemose

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    Mar 26, 2013
    Location:
    Elkton, Maryland
    #10
    Also try removing the power cord and holding the power button with it unplugged for thirty seconds. Then plug it back in and try to start it up!
     
  11. Gooz thread starter macrumors newbie

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    Aug 10, 2014
    #11
    I'll try that too. Thanks.
     
  12. Gooz thread starter macrumors newbie

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    Aug 10, 2014
    #12
    Tried that. No luck. Thanks though. When I got into the inside there's a red light on next to a part of (maybe) the mmory board marked DSB I think? Would this hold any clues I wonder. I aslo tried the other suggestion (Thanks) of holding the power switch. No luck.

    G
     
  13. hamis92 macrumors 6502

    Joined:
    Apr 4, 2007
    Location:
    Finland
    #13
    I had a similar problem with my Power Mac G5 – there was a red light on the logic board and the fans would run at full speed when I powered on the thing. The fix in my case was quite simple.

    When you take off the aluminium side panel, there is this airflow guide (the large translucent plastic part) that comes off next. It has "clips" (for the lack of better word) at the bottom that fit into the holes in the aluminium enclosure. Looking from the outside, the rightmost one of those clips should have a piece of silver tape on it. Check that the tape is not broken.

    Inside the hole where that clip goes is a sensor that monitors whether the airflow guide is in place. The best explanation I can think of is that the sensor is optical and the purpose of the tape is to block its signal – a broken tape might let some light leak through, making the G5 think the airflow guide is not present (someone correct me on this if necessary), hence the fans running at full speed as a safety measure.

    In my case the silver tape was damaged. As soon as I fixed it, everything worked like a charm. Let us know if this works for you! :)
     

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