13 Replies Latest reply: Mar 31, 2012 3:31 PM by BDAqua
cosmichobo Level 3 (515 points)



Woke up this morning to find my G5 was powerless (ie no power).  It is always either awake or sleeping, so thought perhaps there had been a minor power outtage overnight... but it would not turn back on.


(In this case, it had been awake, running "Transmission".  Heard it "ding" to announce finishing a file at about 1am...)


I tried unplugging everything except for the 17" studio display (only had a firewire cable going to a video camera, ethernet cable coming from Airport Extreme Base Station, and USB hard drive attached), and tried again, but still wouldn't turn on.


What do I try next...?  CUDA switch? (Do these machines use one?)






PowerMac 2004 dual 1.8GHz, Mac OS X (10.5.8), 1.25GHz RAM, 2x 1TB WD Green Drives, Stock Vid Card
  • BDAqua Level 10 (122,202 points)

    How to reset the SMU/PMU on a Power Mac G5 (Late 2004) or Power Mac G5 (Late 2005) ...




    Earlier G3, G4, G5 models...




    Is there a red LED lit up on the Logic board when AC is connected?

  • cosmichobo Level 3 (515 points)

    G'day mate,


    Reset the SMU/PMU...


    No good...


    There is no visible lights on the logic board when power is connected...  I couldn't locate the LED itself, but I do recall seeing one during previous voyages inside the machine.



  • BDAqua Level 10 (122,202 points)

    Do you have a multimeter?


    2004 PowerMac G5 PSU pinouts


    "Stuka" wrote:


    A: There is not a single pinout for a G5. It has several connectors that connect to different areas of the board.


    Power Supply P1 Connector
    Pin# Signal Color ------ Pin# Signal Color
    1 +5Vstb Purple --------- 13 GND Black
    2 GND Black ------------- 14 Power ON Green
    3 FANtach White/Yellow -- 15 GND Black
    4 GND Black ------------- 16 Reserved
    5 Reserved -------------- 17 GND Black
    6 GND Black ------------- 18 RTNaud(GND) Black
    7 +12Vaud (12V2) Yellow - 19 GND Black
    8 GND Black ------------- 20 +5V sense Red
    9 +3.3V sense Orange ---- 21 GND Black
    10 GND Black ------------ 22 -12V Blue
    11 GND Black ------------ 23 GND Black
    12 Reserved ------------- 24 Reserved


    Power Supply P2 Connector
    Pin# Signal Color ------- Pin# Signal Color
    1 +3.3V Orange ----------- 9 +5V Red
    2 +3.3V Orange ---------- 10 +5V Red
    3 +3.3V Orange ---------- 11 +5V Red
    4 +3.3V Orange ---------- 12 +12V3 Yellow
    5 Reserve --------------- 13 +12V3 Yellow
    6 +12Vfan Yellow -------- 14 +12V1 Yellow
    7 +12Vfan(12V2) Yellow -- 15 +12V1 Yellow
    8 +25V White ------------ 16 RTNfan(GND) Black


    Power Supply P3 Connector
    Pin# Signal Color ------- Pin# Signal Color
    1 +5V Red ---------------- 5 +5V Red
    2 GND Black -------------- 6 GND Black
    3 GND Black -------------- 7 GND Black
    4 12V2 Yellow ------------ 8 +12V2 Yellow




    dan k





    Not sure how close that is to the 2005 models though.

  • cosmichobo Level 3 (515 points)

    I do have a multi meter, and vague concepts of using one.  :} 


    But just to clarify...


    The PSU is in the base of the computer... so somewhere I should be able to find 3 connectors - a 12 pin, 8 pin, and 4 pin... coming up from below... Y/N


    And I can then disconnect those connectors, and use the multimeter between the individual pins, to the chassis, to determine if there is voltage or continuity (gnd)...  Y/N


    (Or do I need to keep the connectors in place, so as to keep the circuits closed, and push the multi meter needle in to find if there is any power?)



  • BDAqua Level 10 (122,202 points)



    N, you leave them connect I believe & insert a prob into the connection.




    Y, I think so.

  • japamac Level 7 (24,390 points)

    do I need to keep the connectors in place, so as to keep the circuits closed, and push the multi meter needle in to find if there is any power?



    Have you unplugged the mains once? When replugged, is there a click? Perhaps two clicks?

  • cosmichobo Level 3 (515 points)

    Can't say I've heard any clicks....

  • cosmichobo Level 3 (515 points)

    Haven't checked pins yet..


    Left PRAM battery out and power plug pulled overnight....  Still nothing and listened carefully this time - no clicks when reconnected.

  • japamac Level 7 (24,390 points)

    no clicks when reconnected.

    One is common in a normal PSU, two is common in a failed PSU.

    None, well, you don't see any fan or LED activity, right?

    Testing will only confirm what is likely a dead PSU.


    Have you seen this?

    http://damntechnology.blogspot.jp/2009/02/rebuilding-powermac-g5-power-supply.ht ml

  • cosmichobo Level 3 (515 points)

    G'day japamac,


    Well, I guess you get what you pay for... and I paid $99 nearly 2 years ago for a machine labelled "NO WARRANTY" at a pawn broker...  Just asking for trouble...


    Thanks for the link to the PMU rebuild... I can use a soldering iron, but am far from good at it... Think this machine will be getting either parted out, or sold as is for a few bucks to go towards a 2nd hand iMac or Mac Pro...




  • japamac Level 7 (24,390 points)

    That's pretty cheap for two years of use.

    Likely a used PSU would cost more than what you paid for the entire machine.


    The PSU in the G5 has always been a weak link.

  • cosmichobo Level 3 (515 points)

    As an interesting addendum...


    I bought a new dual 1.8GHz G5... just had to insert my optical, hdd, and video card.


    Now, running the same settings etc (as its the same hdd), the machine goes to sleep as it is meant to... whereas before it would not sleep unless told to manually.

  • BDAqua Level 10 (122,202 points)

    Great to hear, thanks for the report.