G5 does not power on

Discussion in 'PowerPC Macs' started by Susurs, Jan 29, 2018.

  1. Susurs macrumors 6502a

    Susurs

    Joined:
    Jun 18, 2010
    #1
    I bought G5 (2003, A1047, Dual 2.0), which was sold as defective - Previous owner told he does not have any idea why the mac does not power on.

    I bought it for a few bucks just for fun.

    To my surprise, the mac instantly turned on when I first powered tried and pressed the power button. I turned it off and on - everything worked prefectly. Played around with OS X 10.5 for a while, unplugged the mac from power cord...Next day it powered on again without any issues and I kept it on for few hours.

    I did not had time to test it again for a week or so.

    Today I tried to power it on again. Connected power cord - heard 2 clicks (that is probably a normal behaviour). Pressed the power button - heard one click/the light went on for a split second/off, and nothing more happens.

    When I keep pressing the power button the light is on untill I release it, but nothing else happens. Upon a repeated single press I hear a click again but the machine does not power on.

    When the lid (and plastic) is off - I see that fans try to start but instantly halt as the power is cut.

    Red light inside the case blinks for a short time as well when the plastic cover is off (It should be on when the plastic is off - normal).

    I started to think what was the factor the mac switched on for two days in row. Even after the power cord was disconnected...

    It was brought to me in cold weather. Placed it near open window for a while (10 minutes or so). Did not work. Maybe have to try for a longer time.

    Reseated RAM, tried different ramsticks - no go.

    Resetted SMU, took out battery - no go.

    Heated memory area on the motherboard with a hairdryer as I red that memory controller might be faulty - no go.

    Out of curiosity... I want to find out the issue... :)

    Any ideas? Can it still be the psu...Even if there seems to be power supplied for a split second?

    Something stops it from booting...and the power is cut off...
     
  2. DeltaMac macrumors G3

    DeltaMac

    Joined:
    Jul 30, 2003
    Location:
    Delaware
    #2
    My guess is the PSU is failing (not yet completely gone, but getting there :rolleyes:.
    I think what you are seeing is the trickle voltage (which detects power, and connection to the logic board.) is working, but the PSU won't handle any load, simply shutting back off.
    And, likely that the G5 was sitting without any power for a few days (or months :D ), and could work for a bit, until a transistor or two, or one or more caps, in the power supply began to break down again
     
  3. ziggy29 macrumors 6502

    Joined:
    Oct 29, 2014
    Location:
    Oregon North Coast
    #3
    Best guess is the PSU, I think. It's possible that some caps in the PSU are failing. I have a G5 that I've parted out which did that -- trickle light comes on, but I could almost never get it to power on.
     
  4. Susurs, Jan 29, 2018
    Last edited: Jan 29, 2018

    Susurs thread starter macrumors 6502a

    Susurs

    Joined:
    Jun 18, 2010
    #4
    My ‘inner self’ believes it has to do something with the PSU as well... :D
    ...Well...An ATX PSU would not be suitable for any tests as far as I understand, right?

    P.S. Oh, well...that thing is ‘well hidden’...found some online guides...the whole mac needs to be ‘teared apart’ to replace the PSU...
     
  5. Susurs, Jan 30, 2018
    Last edited: Jan 30, 2018

    Susurs thread starter macrumors 6502a

    Susurs

    Joined:
    Jun 18, 2010
    #5
    Ok, I have ordered a replacement 600W PSU for this mac. We will see... It should arrive next week...

    Hope this old mac will appreciate all my ‘hard work’ and time being invested towards it’s resurrection... :D

    :apple:
     
  6. eyoungren macrumors Core

    eyoungren

    Joined:
    Aug 31, 2011
    Location:
    ten-zero-eleven-zero-zero by zero-two
    #6
    Any old Mac appreciates being given purpose again. :)
     
  7. AphoticD macrumors 68000

    AphoticD

    Joined:
    Feb 17, 2017
    Location:
    Australia
    #7
    Another G5 on the mend! They are great machines. I’m putting my G5s to use every day and they don’t miss a beat. For the most part, the G5s still keep up well enough without many compromises. Not bad for a computer designed 15 years ago.
     
  8. eastone macrumors newbie

    Joined:
    Feb 23, 2014
    Location:
    Vaasa
    #8
    Did you replace the power supply?
    Any news?
     
  9. Susurs, Feb 15, 2018
    Last edited: Feb 17, 2018

    Susurs thread starter macrumors 6502a

    Susurs

    Joined:
    Jun 18, 2010
    #9
    Received it. Removed the old one, but still didn’t had a time to install a new one. This was/is one busy week...
    Will update info here after I do.
     
  10. Susurs thread starter macrumors 6502a

    Susurs

    Joined:
    Jun 18, 2010
    #10
    It’s up and running! :apple: :)

    Thank you! Installed a ‘new’ PSU and it booted instantly.
     
  11. AphoticD macrumors 68000

    AphoticD

    Joined:
    Feb 17, 2017
    Location:
    Australia
    #11
    Great news! Another resurrected aluminum beast. Time for a photo opportunity to Post Your PowerPC Setup.

    Have fun! :apple:
     
  12. eastone macrumors newbie

    Joined:
    Feb 23, 2014
    Location:
    Vaasa
    #12
    Congrats! :)
    The symptoms in your machine were similar?
     
  13. Susurs thread starter macrumors 6502a

    Susurs

    Joined:
    Jun 18, 2010
    #13
    Yes, just the fans seemed to spin for a split second shorter.
     
  14. eastone macrumors newbie

    Joined:
    Feb 23, 2014
    Location:
    Vaasa
    #14
    I replaced capacitors on the motherboard and voilà :)
     

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13 January 29, 2018