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Adamki2000 · Feb 7, 2005, 10:35 PM

This is a different kind of motherboard upgrading question than any of the others I've been able to find on the 'net and I'm wondering if anyone's ever attempted this before and how successful it may be. I have a slot-loading iMac G3 350MHz machine that I want to upgrade since I don't really have the money to go out and buy a new computer and probably won't be able to for the next year or so at the minimum.

I recently purchased the motherboard pulled from a 600MHz iMac G3 and I was hoping I could figure out how to install it into my machine with no problems. I know that it's not quite as simple as "swap out the old and in with the new" kind of thing but what I really need to know is are there any kind of possible hardware incompatibilities I should be aware of before I try to install this new logic board? The down converter (power board) I think was the same across the entire 350-700MHz iMac line. However, I know there were 2 kinds of CRTs used and therefore 2 analog/video/power boards as well. I know my iMac right now has the LG CRT display and the corresponding PAV board (with the switch for either an LG or CPT CRT). The question is, if I plug the down converter board onto the iMac 600MHz logic board, attach it to my current PAV board and try to power it up, will it work? I'm afriad of blowing out a board or making the CRT explode or something. I doubt it'd be that bad but should all the parts of the iMac 350 be compatible with the newer logic board?

I'd think the answer would theoretically be yes but I don't know. So far I do know that my heat shield had to have the cutout on the back for the VGA port sawed out so it'd fit around the 600MHz logic board and I know that I'm going to have to move the heat sink on the divider panel down just a bit and apply a thermal pad to keep the 600MHz processor from overheating but aside from that, do you guys know if that's all I need to do? No parts of my iMac 350 need to be replaced with newer components from a 600-700MHz iMac?

Thanks for all the help!

MichiganRich · Feb 8, 2005, 12:58 AM

(reply deleted due to rampant sarcasm and mean-spiritedness)

*giggles*

Adamki2000 · Feb 18, 2005, 05:33 PM

Can anyone out there help me? I have the tech service manuals for both my model iMac and the Summer 2001 models but they don't give any info. on whether parts are cross-compatible. I think the biggest issue I need clarification on is what (if any) differences exist between the power/analog/video boards in the 2 different models and if my LG CRT will work with the new logic board. I guess I just need to make sure that my PAV board won't overpower or underpower the later-model logic board. I know this is a very technical issue but any help of any kind is much appreciated!

iREZ · Feb 18, 2005, 06:23 PM

Try the mod forum.

Detrius · Feb 19, 2005, 03:31 PM

The ONLY difference you need to worry about is the processor heatsink. The processors were in two different locations on the boards. As long as the hump that comes up from the frame is in the same location, you are fine. That's all you have to worry about.

Adamki2000 · Feb 19, 2005, 06:32 PM

Oh thank you, thank you, THANK YOU!!!! I was hoping that was all that was needed and that the PAV board would be compatible. Looks like that's the case and I already took care of moving the heatsink down a bit on the divider panel and it's now mounted in it's new position, with fresh thermal pads in place. Now to reassemble it and let you guys know if all goes well as planned! Again, thanks so much for that much-needed information! :-D