Previous 1 2 Next 15 Replies Latest reply: Nov 13, 2011 12:38 PM by MGW
Jowie Level 2 Level 2 (205 points)

Hi all,


I've been having trouble with my old iMac G5 (17" iSight). It wouldn't boot up properly. To make matters worse, the SuperDrive doesn't work properly any more so I can't just boot off the Mac OS install disks.


Here's the story so far:


  • Switched iMac on, chimed, got Apple logo. Fan went crazy and didn't get any further. Tried rebooting a few times but same result.
  • Zapped the PRAM (command-opt-P-R) and tried again, but still no joy.
  • Found some instructions on the web about booting in Open Firmware mode (command-opt-O-F). Tried this, with the reset-nvram and reset-all commands (I think!) and then rebooted. Again, nothing.
  • Decided to be sneaky, using another computer: Switched my PM G5 on in Target Mode, plugged it into the iMac and held down the option/alt key. Chose the PM's Target disk as bootup disk. iMac started up.
  • While it was up and running using my PM's drive as the startup drive, I ran TechTool Pro 4, scanning hardware as well as the iMac's own drive. All passed with flying colours.
  • Ran Disk Utility on iMac disk... Repair Permissions found a few issues but nothing major, and Repair Disk found no errors at all.
  • Rebooted the machine holding down the alt key, selected the iMac drive as the startup disk. Computer booted up successfully. Removed FireWire connection completely.
  • At this point, I thought I was sorted. But the following morning when I tried to boot the machine, it flashed the question mark... Couldn't find the startup disk. So I held down alt again, selected the drive and booted up. At this point I went into the Startup Disk control panel to make sure the internal drive was selected.
  • However... Now since I've rebooted, I get nothing, even on the Startup Disk (alt) screen. The cursor spins for ages, but no drives come up.


So hardware-wise, it seems okay, so I'm guessing it's repairable, don't you think? I did have one thought... The machine's getting on, do you think it might be the PRAM battery?


Thanks for any advice!



iMac, Mac OS X (10.5.8), G5 (17" iSight) 2.5GB / 160GB
  • Jowie Level 2 Level 2 (205 points)

    So, I bought a nice shiny new 250GB WD Caviar Blue and a set of Torx screwdrivers, opened up iFixit and got to work. Installed the new HD with no problems and reassembled the machine.


    I then booted up from a Leopard installer disc (via FW Target drive), formatted the new HD all fine and installed Leopard. When it came time to restart I clicked the button, got a chime and an Apple logo, then... Nothing.


    Waited about 20 minutes, still nothing. In fact, I'm back where I started. Looks like it wasn't the drive after all. Could there be a serious problem with the internal drive bus or the motherboard? Should I give up? I know there's a problem with the optical drive, maybe I should try disconnecting it?


    It's a really weird one, because it sees the internal drive, it'll format the internal drive and it will even install a new OS on the internal drive. And I can boot up from any disk over FW. It just refuses to boot from the internal drive.


    Any ideas would be gratefully received thanks. Otherwise it looks like this old iMac's gonna have to be sold for parts on eBay.

  • MGW Level 7 Level 7 (27,020 points)

    Have you checked to see that the caps are ok, not swollen or leaking?  It could be that th logic board is failing, and the bad caps would contribute to this.


    If you can boot in Target Disk Mode try running Disk Utility to see what's going on.  If that doesn't show anythng, use the Apple Hardware Test disc, which came with your computer.


       1. Insert the Mac OS X Install disc that came with your computer, then restart the computer while holding the C key.

       2. When your computer finishes starting up from the disc, choose Disk Utility from the Installer menu. (In Mac OS X 10.4 or later, you must select your language first.)

          Important: Do not click Continue in the first screen of the Installer. If you do, you must restart from the disc again to access Disk Utility.

       3. Click the First Aid tab.

       4. Click the disclosure triangle to the left of the hard drive icon to display the names of your hard disk volumes and partitions.

       5. Select your Mac OS X volume.

       6. Click Repair. Disk Utility checks and repairs the disk.









  • Jowie Level 2 Level 2 (205 points)

    Hi Miriam,


    Yes I've done all that. In fact, I did both Disk Utility and a full scan using TechTool Pro 4 (see top message). And since I've now changed the HD to a completely new one, I think I can safely rule that out, don't you think?


    What do you mean by caps? Can you tell me how to check if there is a problem with them? I don't know where to look... Thanks!

  • MGW Level 7 Level 7 (27,020 points)

    Caps are capacitors, those things that look like little soda cans.  They are on the logic board and inside the power supply unit.  If they're either swollen or leaking, they con compromise your machine.  Here's a picture.







  • christopher rigby1 Level 4 Level 4 (2,100 points)

    I'm going to give you my own tale of woe. My G5 iMac died after a power cut (totally dead - nothing at all). The repairers replaced the power supply and also put in a bigger HD (I needed one anyway).


    After a few days with everything running fine, I began to get issues like yours. Bootup and login problems. Eventually I was running continuously in Safe Mode and not putting it to sleep overnight. Then I began to get problems like saving or pasting - I tried a Restart but it wouldn't log me back in. However, I could run Tiger on an eHD for a while, but then the FireWire ports went too, so I was stuffed.


    It turned out to be the logic board. I bought a recon machine - same spec - on eBay, installed my new HD in that, and I was up and running again. So far (touch wood) it's ok. I think that's your issue. There's something amiss with the logic board. How far you want, or can, go down the path of getting a replacement is of course up to you.

  • Jowie Level 2 Level 2 (205 points)

    That's interesting to know, thanks! I will open it up again in a bit and have a look. If it looks like the capacitors are on their way out, I'll stick it on eBay for parts...

  • Jowie Level 2 Level 2 (205 points)

    Thanks for your information. To be honest, the machine was getting to be too slow for everyday use... Watching YouTube videos and the like were jumpy. So we've gone and ordered a newer iMac off eBay (Aluminium Core 2 Duo) to replace it with. It was going to happen at some point, but because it's gone wrong it just needed to be sorted sooner rather than later.


    So I'll see what I can do to repair this one first... If I can I may even consider running it as a server machine!


    Will let you know how I get on

  • christopher rigby1 Level 4 Level 4 (2,100 points)

    Yes, it's amazing what difference a graphics card can make. I have a little HP netbook (very recent) running Windows 7 - the G5 still has it licked in most departments, but the HP runs video much smoother. I guess its low grade Intel integrated GFX chip still smacks the bottom of a state-of-the-art (for 2006) ATI Radeon X600 Pro.

  • Jowie Level 2 Level 2 (205 points)

    Hi again,



    I know it's been months! I kept putting off the terrible deed of taking the iMac apart because I knew that in order to get to the capacitors it's quite a job... Anyway... I finally did it today. I don't know much about "caps" but these look a little bit dodgy:





    and C1309



    So I'm guessing these caps have gone? Is it worth a repair, or shall I just stick it on eBay for parts?

  • MGW Level 7 Level 7 (27,020 points)

    The caps are indeed gone, swollen and leaking! Nasty!  Replacing the logic board is not inexpensive, you are probably, best off by selling it for parts.







  • Cattus Thraex Level 4 Level 4 (1,715 points)

    G5’s were wonderful machines, unfortunately I have the feeling yours is too ill for a reasonable action to repair it. Some luck if you find a similar product, and take the logic board from that one. Otheerwise MGW is of course right, sell it for parts, which is the reverse sense of action.

  • Jowie Level 2 Level 2 (205 points)

    Oh really? I'm surprised by that... That link you sent me to the guy on Flickr, it looked like he had much worse problems than me, and he got them replaced. Do you think it's not worth getting it sorted?


    No worries if not though... Like I said, we got a replacement machine (nice shiny iMac 20" C2D) and the poor old G5 has been sitting behind a bedroom door since the beginning of July anyway! Would've been good to fix it up, even if just to make a bit of money back on it on eBay, or to keep it as a server machine. But if all it's good for is parts, then I guess that's better than nothing!

  • Cattus Thraex Level 4 Level 4 (1,715 points)

    Give a try, G5s are wonderful machines, I still have a 12 in PowerBook for older apps, including classics. If not expensive, it is indeed worth trying.

  • Jowie Level 2 Level 2 (205 points)

    I think I'd have to defer to the expertise of an electronics buff though... Don't think I've picked up a soldering iron in about 20 years

Previous 1 2 Next