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Thread: G5 won't boot

  1. #1

    Member Since
    Mar 05, 2011
    G5 won't boot

    I'm having major problems with my G5. I tried to restart into safe mode and now It won't load past the grey Apple screen. It's the same problem people have a lot where it just shows an Apple logo nothing else and eventually the fans get really loud.

    I think the logic board has gone but I'm hoping someone can tell me about something I haven't tried.

    I bought this machine second hand so unfortunately I don't know its age but its a 1.6 if that helps.

    Here's what I've tried so far:

    Reset PRAM
    Reset PMU by button inside
    Reset SMU
    Reset NVRAM from open firmware which it lets me access [also did reset-all in here]
    Reseated PRAM battery
    Left PRAM battery out for 24 hrs and tried reseating again
    Haven't had chance to test he battery with a multimeter yet so there;s
    Removed everything except keyboard, monitor and power cable
    Took out all parts and cleaned dust out, though it wasn't too bad.
    Took out CPU to check for dirt or damage though there wasn't any. Reseated
    Removed graphics card hoping to vnc into it, but nothing and eventually fans get loud again
    Tried booting in verbose mode but didn't work
    Tried booting from OSX disk but didn't work
    Couldn't run AHT from disk
    Was able to get to startup manager, showed my normal startup HD but didn't show OSX disk
    Target disk into it from another mac worked and HDs appear to be fine
    Tried taking out secondary HD and swapping startup disk into different bay
    Tried many different combinations of RAM. There are 4x256 sticks in pairs from 2 manufacturers.
    With anything less than all 4 I can't even get it to chime and the power light flashes once every 4-5 seconds making me think this could be a RAM problem though there isn't much info on 4-5 flashes anywhere on the web.

    Any ideas?

    It's probably worth mentioning that I use this as a home server and I leave it on all the time. I've had it around 4 months and its probably been off for a max of 10 minutes in that time, added to however old it is. So there is a possibility this is a burnt out cap somewhere. I'm confident of replacing it, but finding it would probably be quite difficult so any tips or advice on that would be much appreciated.

    Thanks in advance for any help

  2. #2

    harryb2448's Avatar
    Member Since
    Nov 28, 2007
    Nambucca Heads Australia
    iMac i5 2.7GHz, 16GB memory, OS 10.11.1.
    Here is a link to diagnose flashing power light.

    From what you say may be a memory problem. Remove it all and see if you get the alarm on rebooting.
    Hang on to those original install discs like grim death! Using OS X.7 or later make a bootable USB thumb drive before running Installer!

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