20 inch iMac g4 USB 2.0 logic board in a 17 inch 1.25ghz imac body?

Discussion in 'Apple Collectors' started by BittenApple, Jul 25, 2014.

  1. BittenApple macrumors 6502a

    BittenApple

    Joined:
    Nov 29, 2008
    #1
    20 inch iMac g4 USB 2.0 logic board in a 17 inch 1.25ghz imac body?

    having a hard time figuring out all the PN for the USB 2.0 iMac G4 and which boards are compatible with my body.
    thanks
     
  2. Intell macrumors P6

    Intell

    Joined:
    Jan 24, 2010
    Location:
    Inside
    #2
    I believe the USB 2 17" and 20" G4 iMac have swappable logicboards. I think even the USB 2 15" is swappable, but no other models can be swapped into a USB 2 model's dome.
     
  3. BittenApple thread starter macrumors 6502a

    BittenApple

    Joined:
    Nov 29, 2008
    #3
    Thanks. They layouts of the chips look exactly the same on my current motherboard as on the ebay listings that are listed as 20 inch logic boards..

    also my motherboard came with bluetooth on board. is this is a separate chip or soldered onto the board? thanks again

    no worries about eec codes?

    do the different colored heatsinks mean anything?
     
  4. Intell macrumors P6

    Intell

    Joined:
    Jan 24, 2010
    Location:
    Inside
    #4
    The Bluetooth in on a separate board on the bottom of the logicboard. You have a few options when it comes to the Bluetooth for the new logicboard. Option 1: Don't install it.
    Option 2: Install the current Bluetooth board from the old logicboard to the new.
    Option 3: Purchase a Bluetooth 1.X board for use with the new logicboard.
    Option 4: Purchase a Bluetooth 2.X board for use with the new logicboard.
    Option 5: Use a USB Bluetooth dongle.

    For the ECC codes, there won't be any problem. They are dynamically read and the system changes to them. I don't think the different colour heatsinks mean anything, I could be wrong about this one.
     
  5. 666sheep macrumors 68040

    666sheep

    Joined:
    Dec 7, 2009
    Location:
    Poland
    #5
    IIRC PSU connectors do differ between 17" and 20".
     
  6. BittenApple thread starter macrumors 6502a

    BittenApple

    Joined:
    Nov 29, 2008
    #6
    they look identical in pictures? are they wired differently? or could this be a pre usb 2.0 distinction?
     
  7. MacTech68 macrumors 68000

    MacTech68

    Joined:
    Mar 16, 2008
    Location:
    Australia, Perth
    #7
    I assume you're looking for a replacement logic board for your EXISTING 17" 1.25Ghz G4 iMac?

    There were 5 logic boards for the USB2 iMac G4.

    Originally, Apple released a 15" & 17" only, in Sept 2003.

    Later, when the 20" was released, new motherboards appeared for the 15" & 17" (as well as one for the new 20" model).

    A new neck assembly was created for the 20". These assemblies include the display cabling and are different for the 15", 17" and 20".

    Why the 15" and 17" boards were changed is something I can't determine. None of the specs changed as far as I can tell, though the later versions would have shipped with 10.3.1 instead of 10.2.7.

    The power supplies were different part numbers for the 20" vs the 17" & 15", but I'm not sure if the pinouts were exactly the same, although the 12v and ground certainly ARE the same pinouts. I'd assume the difference is to drive the larger display, especially the higher requirements of the backlight on the 20".

    What DOES scare me a little is that the bottom housing (the very base of the whole machine) is a different part number from the 17" to the 20". Just why this is is also a mystery, but may indicate a small difference in logic board mounting, or a difference in attachment with the faraday cage which is another part that differs from the 17" to the 20".

    One thing that does worry me is TDMS "swing". There seems to be two settings for this, and I can't determine which setting is for which display. It appears that this is a difference in the voltage used for the serial TDMS bus. If the wrong display is connected, you could destroy the display.

    Without more info, I'd stick to the logic board your machine originally shipped with. IE, exchange like for like.
     
  8. BittenApple thread starter macrumors 6502a

    BittenApple

    Joined:
    Nov 29, 2008
    #8
    So physically all the USB 2.0 iMac G4 have the same connectors for the video display and the PSU but cannot be used between each other because of the cabling being wired differently?
     
  9. MacTech68 macrumors 68000

    MacTech68

    Joined:
    Mar 16, 2008
    Location:
    Australia, Perth
    #9
    Not quite.

    The designs appear to be roughly the same, but there are differences that may mean using a 20" logic board in a 17" chassis may;

    1). not work

    2). not physically fit

    3). damage the display.
     
  10. BittenApple thread starter macrumors 6502a

    BittenApple

    Joined:
    Nov 29, 2008
    #10
    Thanks for your help. There seems to be a lot of 20 inch logic boards on ebay but none for the 17 inch version. Ill just have to be patient. Thanks again everyone!
     
  11. HereBeMonsters macrumors 6502

    HereBeMonsters

    Joined:
    Jul 5, 2012
    Location:
    Fareham, UK
    #11
    Where are you? I've got a 17" G4 that I'm parting out. If in the UK, I'll send it out to you.
     
  12. ZombieZapper macrumors newbie

    ZombieZapper

    Joined:
    May 7, 2017
    #12
    Hi, do you still have the iMac G4 logic board? I know this post is almost 3 years old...
     

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