10 Replies Latest reply: Oct 2, 2011 10:38 AM by BDAqua
Dementedioser Level 1 (0 points)

I amd completly new to Mac computers.

I just recently got a used Power Mac G5, what im going to assume is an early 2005 model (2.3 GHz Dual processor). Opened it up, cleaned out dust, then closed it and powered it on. To my dismay, it did not. The fans are blowing at full speed as soon as i turn it on, The power LED only stays on if the button is pushed and held down. It has no video, no chime, just fans blowing. I have no idea what could be wrong with it. I have taken out the RAM and Video card and reseated them with no results. If i could get any help on this i would greatly appreciate it.


It has no OS on it right now, 3.5 GB RAM, one 1TB HDD and one 500GB HDD.

  • BDAqua Level 10 (122,286 points)

    Hi & a warm welcome to the Forums & Macdom!


    Without an OS to control the Fans it's normal for them to go into high gesr for safety.


    You might get some bare useless video with one of these boot options...


    Hold the Option/alt key at bootup.


    Does it boot to Single User Mode, CMD+s keys at bootup, if so try...


    /sbin/fsck -fy


    Repeat until it shows no errors fixed.


    (Space between fsck AND -fy important).


    Resolve startup issues and perform disk maintenance with Disk Utility and fsck...




    Might be time to replace the PRAM Battery, 4 years is close to their lifespan, far less if ever without AC power, & can cause strange startup problems...


    See which one your G5 has...






    Still, without an Install Disc, you're up a creek, G5s can run 10.3, 10.4, or 10.5, trouble is finding a reasonally priced version of the Retail versions, since Apple no longer sells them.

  • old comm guy Level 4 (2,240 points)

    Was the machine supposed to have been running before you acquired it?  If not, then we'll start at the beginning.


    When a G5 powers up, the white LED over the power switch should come on when the button is pushed, then as things get started, it should stay lit.  The fans will want to run up to full speed, but initially the PMU or SMU will ramp those fans back down and start a watchdog timer which is reset periodically by the operating system when fan control commands are written to the PMU or SMU. 


    Since the fans are not ramping down for a little while, that is first suggestive that the PMU or SMU is not coming up.  The first thing you need to do is to verify the PRAM battery condition, as a weak battery can cause all sorts of mischief.  One does that by measuring the voltage on the battery while in its holder with the AC power disconnected from the computer.  The voltage should be somewhere between 3.3 and 3.7 volts.  If it is below 3.3 volts, the battery needs to be replaced.


    If the PRAM battery is OK, then you need to try a PMU or SMU reset (information at links).  For the machine you describe, I believe the SMU reset is what you need to do.  If  the management unit is successfully reset and actually working, you should now have the machine power up and at least the fans should come down for a little bit.  Since there is no OS on the machine, what should happen is a boot tone (chime) sounds, the video comes up and then there should be video with a folder and flashing question mark appearing, indicating no bootable OS was found.


    Not saying that the above guarantees success; it's just that those are the first steps that need to be taken to see if the machine can be revived.

  • Dementedioser Level 1 (0 points)

    Hi and thanks for the welcome and quick response, I just replaced the PRAM battery this morning and got no change. I also tried what Old Comm Guy said, which was a PMU reset with no results either, I cannot boot into anything. So im not sure if holding down the Option/alt key is doing anything, and i get no video so im not sure if i can type anything.


    I'm not entirely sure if the unit was supposed to actually work to begin with, I got it from the best buy employee auction, So i dont know if by "tested working" meant "unit shows slight signs of life"  And it also came with the restore CDs (I guess I should have mentioned that as well, Sorry)

  • BDAqua Level 10 (122,286 points)
    "unit shows slight signs of life"

    Not a great thing, especially with a G5!


    Do you have another Mac around with Firewire, or an enclosre you can pull the Hard Drive out & we can try to inspect the system.log for possible clues if there are any?

  • Dementedioser Level 1 (0 points)

    No i do not, this is the first Mac Ive ever owned. Ive pulled out almost everything checking to see if anything could be messing it up. Only thing i havnt completely taken out was the ram and the processors... Im not getting any kind of response out of this computer.

  • BDAqua Level 10 (122,286 points)

    So sory to hear your first Msc experience is going so badly!


    Is there at least one red LED lit up on the Logic board if you open the side panel whike plugged in?


    Does the Power button light up when pressed? Does it pulse/flash?

  • Dementedioser Level 1 (0 points)

    Well i kind of asked for it when buying a used Mac.


    Theres one red LED on that ive determined to be the plastic air deflector thing being out of place, once that plastic piece is reseated the LED would go off.


    The power button will only light up if the button is pushed, Once the button is let go the light turns off but the fans continue spinning, No pulsing/flashing of the Power button light.


    I appreciate the quick answers im getting here, its a nice welcome indeed, thank you.

  • BDAqua Level 10 (122,286 points)

    Well, the logic board seems to be getting some power for that LED anyway, could be that little power button, or can you check voltages?


    Pin 14 is PWRON, and...




    https://discussions.apple.com/message/11980210?messageID=11980210#11980210?messa geID=11980210

  • Dementedioser Level 1 (0 points)

    I do not have a Multimeter here at my home, so i do not have a way of checking voltage.


    Unfortunately I do not have the time and money I would like to put into this baby. I only have a 14 day return period so it seems that im going to have to return it. I intend on reading more into Macs, Ive always wanted one, and have complete intentions of still getting a new one. Thank you so much for your time and effort.

  • BDAqua Level 10 (122,286 points)

    OK, good idea on the return, good luck too!