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

BittenApple

macrumors 6502a
Original poster
Nov 29, 2008
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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
 

Intell

macrumors P6
Jan 24, 2010
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Inside
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.
 

BittenApple

macrumors 6502a
Original poster
Nov 29, 2008
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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.
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?
 

Intell

macrumors P6
Jan 24, 2010
18,872
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Inside
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.
 

MacTech68

macrumors 68020
Mar 16, 2008
2,185
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Australia, Perth
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.
 

BittenApple

macrumors 6502a
Original poster
Nov 29, 2008
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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?
 

MacTech68

macrumors 68020
Mar 16, 2008
2,185
149
Australia, Perth
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.
 

BittenApple

macrumors 6502a
Original poster
Nov 29, 2008
999
499
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.
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!
 

Expobill

Suspended
May 30, 2018
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Im looking for one as well. as the eskimos say on every Feb 14th, my igloo needs some loving!