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Excellent write-up on LCS Servicing, Quad G5

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There are a handful of us who like the G5, and want to keep the machines running. The rest of you can ignore this post!


The following link could be of use to someone trying to quieten a Quad G5, and to prolong its life: http://www.saunalahti.fi/~holindho/g5-quad-v1-lcs-repair.html . Notice the graphs at the foot of the page, as 10ºC lower CPU temperatures at idle and 40ºC lower under load would make all the difference in dealing with fan noise. There are some further links re. cooling systems in the G5 at the bottom.


I have serviced three air cooled units (essentially just thermal grease renewal and cleaning out dust, followed by recalibration) with excellent results, and these are very easily done (contrary to what some people think), but the liquid cooled systems especially make people shudder. The writeup takes much of the complexity out of the whole question.


I believe that there were two LCS systems in the Quad G5, so be aware of that — your LCS may differ. All the same, the author has documented not only the basic plumbing and mechanicals, but crucially, the presence of sediments in the radiator fluid used after several years, leading to clogged filters. There will be a related need to clean out the radiator and clean or renew the hoses.


As in your car's cooling system, the lifespan of radiator fluids is limited, and when sedimentation occurs, the works are bound to get gummed up. The key thing in the LCS is to keep it running optimally, as the temperature thresholds are really rather slender, so this is good to know about.


My "new" Quad G5 is still working well, but it could still afford to run at slightly lower temps, so methinks I'm going to service it sometime over the coming months.

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On 10/29/2018 at 9:27 PM, Franklinstein said:

Original link is dead as of 30 Oct 18 and apparently since at least 2017. Archive has it from April 2014. Does someone [read: admin-type person] want to preserve it or copy/paste the info here?

I would also like to see it.


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I recently picked up a Dual 2.5Ghz G5. Of course all the coolant leaked out corrosion has only affected both cpus and I cleaned them up. Board is still mint and the PSU although Dirty seems fine. I need to figure out how to rebuilt the cooling system as well, mine differs slightly from this post.

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  • 68kMLA Supporter

Oh nice, thanks for the great tips. I have a LCS in a box that needs repairs, glad I kept it when I replaced the current one.

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Unfortunately many of the images in the archived page are now gone. So I got in touch with the original author, and apparently he had been planning on moving the now defunct pages to his new domain. My query prompted him to finally do it! Here are the new links:


Main LCS repair article: https://h-lindholm.net/articles/g5-quad-lcs-repair/g5-quad-v1-lcs-repair.html

Pump repair article: https://h-lindholm.net/articles/g5-quad-lcs-repair/g5-quad-v1-lcs-repair-pump.html

The stress test live CD made for the project: https://h-lindholm.net/articles/g5-quad-lcs-repair/stress-v2.iso.bz2


My G5 quad definitely needs a rebuild as it is failing its thermal calibration. I'm planning on doing something closer to the following with clear tubing and what looks like a reservoir.

My G5 is my bridge machine and I barely use it because of how loud it gets. Hopefully this rebuild will help.


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