5 Replies Latest reply: Jun 17, 2012 7:59 PM by rccharles
levelheaded Level 1 Level 1

Hi,maybe some advice please.

I have an imac 20" G5 als.running 10.5.8 The problem is that when I startup it goes to the flashing questionmark mode.I will explain what i have done so far.When this first happened I thought that the drive was playing up,so I attempted to install the system disk OSX but it was having none of it.after trying lots of times it eventually loaded,and I went to disk utillity,but it never saw the hard drive,so I thought that it must be the drive.The diagnostic light inside on the logic board were lit up as they should be.I purchased a new drive,and a battery for the logic board just in case,I installed the battery,and the new drive and started up,but yet again it went to the flashing questionmark.I shut down and started into the startup manager screen where I got a blue screen with a refresh symbol on the left and an arrow on the right but nothing where the drive should be seen.I reset the pram,and tried to start in safe mode which all brought me back to the questionmark .As a last resort I then installed a drive I knew was working because I replaced it for a larger one,and the exact same thing is happening and the system disk refuses to load.Can anyone tell me if I am doing things in the correct order,or I have missed something simple that I could try.I have installed a drives before with no recognition problems.If i get any answers I would be happy.Thanks

iMac, Mac OS X (10.5.8)
  • rccharles Level 6 Level 6
    Classic Mac OS

    The question mark means the the startup manager could not find a valid OS.


    Could be a bad disk controller. Jumpers not set correctly. ETC.


    I'd try an external firewire harddrive.  PPC needs firewire to boot an exernal drive. 


    I'd try hardware diagnostics.


    I assume it will run the boot dvd OK.



  • levelheaded Level 1 Level 1

    Thanks for replying Robert,

    The OSX disk is not booting from the built in superdrive,I can hear the drive working and the disk spinning but then it just ejects the disk.However,I have got an external firewire drive which I can try tho I use it for timeline backups.Ok Robert thanks for your help, I will try the external drive and go from there


  • rccharles Level 6 Level 6
    Classic Mac OS

    I think if you do an archive & install on the external drive, you will perserver the data on the drive.


    You need to be able to boot from a dvd in order to install software on the external drive.


    I'd say that if you cannot boot from the hd and from a dvd that the machine has more basic problem with the logic board.  Look at capacitor & see if they are distorted.  See Internet !?!






    Sometimes if volumes don't appear in Startup Manager (what you get when you hold down the Option key at startup), you need to reset the Mac's PRAM, NVRAM, and Open Firmware. Shut down the Mac, then power it up, and before the screen lights up, quickly hold down the Command, Option, P, and R keys, until the Mac has chimed twice more after the powerup chime. Then, before the screen lights up, hold down Command-Option-O-F until the Open Firmware screen appears. Then enter these lines, pressing Return after each one:






    "The reset-all command should restart your Mac. If so, you have successfully reset the Open Firmware settings."



    How to eject a cd from the internal cd drive:

    eject cd


    List of devices:



    List of variables:




    ( nvram is the equivalent Mac OS X terminal command. )


    Resetting your Mac's PRAM and NVRAM




    reset the PMU


  • levelheaded Level 1 Level 1

    Hi robert,

       ok I followed your reset instructions,and it hard to explain what happening ,but the computer does find the hard drive sometimes,maybe after 10-15 goes at starting it up and sometimes when i keep putting the system disk in the drive .it always spits out the disk then it will suddenly startup.What i have noticed tho is after reading stuff about these logic boards the capacitors on the boards do leak,and on mine there must be 5 or 6 thet have been or are leaking from the top of the capacitor.I have not checked the ones on the power unit yet,so i suspect that it could be the same.I did forget to mention before that this model was one of those that had faulty psu's or logic boards and i did take it in and they repaired it at their expense,but that was 3 ir 4 years ago now ..So would you think that the leaking capacitors could be the main problem with my G5?

  • rccharles Level 6 Level 6
    Classic Mac OS

    Seems reasonable.  Don't know symptoms.


    There are replacement kits if you are handy with a soldering iron.