Results 1 to 10 of 10

Thread: iMac G5 PSU

  1. #1


    Member Since
    Apr 05, 2009
    Location
    Argentina
    Posts
    65
    iMac G5 PSU
    I have an iMac G5 20" (actually a friend's), that I believe has a faulty PSU. I opened it up, removed the PSU and -to my surprise- I found it's got a standard ATX 20pin power connector! For troubleshooting purposes, could I plug a standard PC PSU (more specifically, my OCZ Z 850W PSU) into the thing and thous isolate the PSU issue? From what I can tell, it should work, but I'm worried about the iMac using some special voltage rail or something, anyone got some info on this?

  2. #2

    Buzzard2010's Avatar
    Member Since
    Oct 22, 2010
    Location
    Bretforton, Worcestershire
    Posts
    2,571
    Specs:
    MacBook Pro 15" 2014, 2.2GHz i7, 16GB RAM, 250GB SSD, OSX 10.9.5 - iPhone 5s 16gb
    As long as the voltage supplies are the same as used by the faulty one it shouldn't be a problem at all.

    - Simon

    If you have been helped, don't forget to use the Reputation system at the top right of their post.
    May 2011
    Nominated: March 2011 & April 2011

  3. #3


    Member Since
    Apr 05, 2009
    Location
    Argentina
    Posts
    65
    The voltages are the same, but the pinouts are different (or so I read online). I'm going to try to test them both with a multimeter, and then modify a 24 pin to 20 pin adapted so that they're the same. I also am going to have to configure screen sharing, since I don't have a 24v rail on my PSU (the iMac appears to need one for the display backlight (or maybe, since it's the backlight after all, I can use it without).
    Any help/tips on this project will be highly appreciated. Right now, I'm searching for the right pinout specs, to compare with multimeter readings.

  4. #4

    harryb2448's Avatar
    Member Since
    Nov 28, 2007
    Location
    Nambucca Heads Australia
    Posts
    21,705
    Specs:
    Imac 27" Retina 3.3GHz, 512GB Flash, 16GB memory, OS X.11.4.
    Quite common to replace G5 iMac PSU with an ATX. This may help:-


    https://supercollidercomputers.wordp...-atx-external/
    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!

  5. #5


    Member Since
    Apr 05, 2009
    Location
    Argentina
    Posts
    65
    Quote Originally Posted by harryb2448 View Post
    Quite common to replace G5 iMac PSU with an ATX. This may help:-


    https://supercollidercomputers.wordp...-atx-external/
    Yes, it can be done without much effort. However, for a permanent solution, both PSUs are still necessary: no ATX PSU has a 24v rail.

    I checked the pinout on my iMac PSU, and it matches that one. My multimeter also reported crazy voltages on the 12v and 5v rails (13.7v and 5.9v respectively, also, the 24v rail is running at 26v, so I could't use this PSU anyways, I'd have to end up getting a DC upscale after all).

  6. #6

    chscag's Avatar
    Member Since
    Jan 23, 2008
    Location
    Fort Worth, Texas
    Posts
    47,988
    Specs:
    Late 2013 27" iMac, iPad 3, iPhone 6s+, iPhone 6+, 3 iPods, El Capitan
    The rails will always read higher until loaded down. Those voltage readings seem normal for an unloaded PS circuit.

  7. #7


    Member Since
    Apr 05, 2009
    Location
    Argentina
    Posts
    65
    Quote Originally Posted by chscag View Post
    The rails will always read higher until loaded down. Those voltage readings seem normal for an unloaded PS circuit.
    Ok, didn't know that, thanks. I contacted the owner of the iMac, and he pretty much said "do whatever you wan't, and if you can't fix it, keep it". Personally, I'd buy an ATX PSU and mod it to work with the iMac, and either have both PSU's hooked up, or buy an upscaled, or an external AC 240v > DC 24v adapter. So now I'm on the lookout for a cheap ATX PSU for this thing .

  8. #8


    Member Since
    Dec 13, 2009
    Posts
    176
    Specs:
    iMAc 1.8GHz PowerPC G5, 2GB, 10.5.8
    These machines had a lot of power supply problems, particularly a bad capacitor supplier. Just google "iMac G5 power supply" and you'll find all kinds of stuff. One fellow fixed his for $51 worth of capacitors (PM me if you can't find that).

    It seems you can also get replacements for the Apple supply-that seems a LOT easier than monkeying with not-the-right-thing from ATX.

    This fellow sells reconditioned $89, or fix yours for $59, but he is in America.
    http://natramelec.com/g5powersupply/g520.htm
    Some eBay sellers might ship to Argentina.

    Buena suerte!

  9. #9


    Member Since
    Apr 05, 2009
    Location
    Argentina
    Posts
    65
    Ughh, Safari just crashed on me and I lost my beautiful response.
    Short version:
    It worked, but not the display (I didn't even try it, since the PSU I bought has only 8A on the 12v rail, I should have checked it first), I'm using screen sharing to control it.
    So now I need some info on:
    DC 12v >24v upscalers. Do these exist? How big are they? Would it fit inside the iMac, so that I only need one power connector?
    Also, I'm looking to see if there is any small form factor PSU that would fit inside the iMac, and, maybe even inside the actual iMac PSU frame. Any info greatly appreciated. If it's a little wider (i.e.: the back cover does't fit back on with it inside), I guess that's OK, since I can always cut a chunk out of the back case and leave that exposed (I would probably have to invent some kind of cover for it, for safety ). The measurements are: 1.7" deep (from screen towards back cover), 7.2" wide (from one side of the iMac towards the next) and 3.1" long (from the bottom stand-side of the iMac towards the top of the screen).

  10. #10


    Member Since
    Apr 05, 2009
    Location
    Argentina
    Posts
    65
    Guys, do you think that this: 200 Watt DC-DC ATX PSU + a 12v ~18A AC-DC adapter work? I could then easily fit it inside the iMac, and have the AC adapter on the outside... what's more, I'd have room for that 12v > 24v up converter (waiting for info on that).
    Here's the link to the specific ebay item I'd buy: http://cgi.ebay.com/200W-12V-DC-DC-M...#ht_2472wt_754.

    Incase anyone tries this (or something similar) in the future, this link should come in handy: http://pcbheaven.com/exppages/Reuse_...ex_connectors/

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Imac G5 help. Suspect faulty psu?
    By djkus in forum Apple Desktops
    Replies: 11
    Last Post: 03-18-2012, 09:20 PM
  2. g5 imac isight psu gone.. again!
    By djkus in forum Apple Desktops
    Replies: 0
    Last Post: 11-02-2011, 09:14 AM
  3. Intel iMac (2006) power cuts out - PSU?
    By Leggie in forum Apple Desktops
    Replies: 5
    Last Post: 01-28-2011, 12:42 PM
  4. iMac G5 turns of randomly - PSU fault????
    By bewarned in forum Apple Desktops
    Replies: 2
    Last Post: 09-14-2010, 08:48 PM
  5. Replacing the PSU
    By DarkDTSHD in forum Apple Desktops
    Replies: 5
    Last Post: 07-22-2007, 08:54 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •