Classic Mac Hardware (Troubleshooting, Upgrading, & Modifying) > General Hardware Discussions

HOT MINI? (Definitive Step-by-Step Guide to Thermal Paste Mac mini G4 CPU)

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FBz:
“Guess what’s on now…” -FGTH

G4 Mac Mini Heatsink Removal, Re-paste and Replace.

Considering that there have now been nearly 50,000 downloads of the Mac OS 9.2.2 (Mac mini PPC G4 Only) Install Image since 2018 AND that these G4 Mac minis are now nearly 20 years old… maybe yours is long overdue to have its’ heatsink cleaned & re-pasted?

You may have your own method for doing this (or have simply avoided it because it seems a daunting task?). Well the first time is a bit nerve-racking but after that… not so much. BUT it must be done.

Check your fan’s exhaust temperature and if it quickly rises to anything above 100˚F / 37.8˚C within the first 10-15 minutes after a cold boot - it’s time to take steps to avoid the CPU “China Syndrome” - while the thing can still boot. I use an infrared thermometer or one of those round dial HVAC thermometers (http://macos9lives.com/smforum/index.php?action=dlattach;topic=5955.0;attach=12782;image) or if you haven’t either of those handy… an oven temperature thermometer - or possibly even a regular body temp thermometer (glass ones might break). I placed a digital body temp thermometer in my coffee this morning and its’ range pegged out @ 105˚F. (So even those might work safely for this.) But really, if you’ve had your G4 Mac mini for more than 4 years - or you use it extensively… it’s best to replace the paste anyway. Especially if you have never done so.

Here Goes…

Once you get your mini stripped down to the motherboard you’ll see the four little plastic spring rivet fasteners (“push pins”) or whatever they’re called… and that’s where the real fun begins.

Again, you may have your own approach to this task, or there may even be a special tool.
In either case, speak up and let the rest of us know!
How do YOU do it?

ADDENDUM: Okay ‘ave described another approach that doesn’t require squeezing with needle-nosed pliers, hemostats, etc. AND possibly without the aid of any visual magnification dee-vices. BUT… do read through all of this mish-mosh first, perhaps as a primer - then go to (Reply #10 below). http://macos9lives.com/smforum/index.php/topic,6875.msg52691.html#msg52691 - FdB

   

Notice the top of the little “winged demon” retainer pin (lower right inset above).


Squeeze the Wings and Push Down on the Heads
Sometime - it’s good to also wiggle the pins in the grasp of hemostats while also pushing down.

After removing the motherboard, place it top down on a terry cloth towel. (No towel in pic below.)

   

The green outlined area above is where you’ll focus your attention to see the red-dotted retainers
(dotted below). Those are the four “wing-ended” pins that need be compressed in order to push them
through the mobo to release the heatsink. (See mobo top view, first shown above / lower right corner
inset.) I use a pretty small pair of hemostats to squeeze those wings in enough that I can then push
each pin down and through the mobo. An opti-visor magnifier is also handy to see those little wings
because sometimes one wing will compress enough and the other one doesn’t. In that case, I’ll use
a small screwdriver or spudger to press that second wing in, while still applying downward pressure
… as the other wing has already started down (hopefully) and partially into and through the mobo.

Some might be able to do this without magnification? My eyes are no longer that sharp - which is
why I use the opti-visor. And it is a two-handed task.

Hemostats are held near-parallel to the board (sideways) to squeeze the pins so that you can push
down with whatever you’re using to push the pins down from above and (again, hopefully) through
the mobo.

You might notice below, the wings on the upper left pin are fully extended, while others may not be.

Other things to watch for are: C573, C567, C447 and C452. You CAN turn the pins using hemostats
BEFORE - in order to get the best angle of attack that won’t interfere with those. I have seen some
of those missing. Likely from being “scraped” off while trying to squeeze wings and push the pins
through. (OR maybe from excessive heat - via paste that needed renewed but wasn’t.) Your mini
will not boot without these. Notice them before you start squeezing and pushing pins downwards.

*Asterisks alongside images denote “clickable” for MUCH larger views.

    *

I have been using one chop-stick for the downward pressure - but today I opted for a pencil with
the lead flattened / no longer pointed (with sandpaper). I like this better than the one chop stick.

   

Now, I have found some other spring-loaded pins but they’re all listed as 18.6mm and there’s no
mention of their shaft’s diameter. I have yet to maim any pins to the point they needed replacing
BUT if anyone has tried the 18.6mm pins… DO speak up. Have seen mention that small nylon
nuts & bolts can be used… and have even heard of using zip ties as substitutes. :o

Mother is the necessity of invention after all.

   

   

Not Stuck?

Now if your paste has never been renewed, you won’t likely see something like the image below.
Instead you will see a sort of thin black film (original heatsink material) surrounding what you can
see as a faint outline (below) of the processor. I use cotton balls soaked in isopropyl alcohol (91%)
to lightly remove this film, with several passes and fresh cotton balls, until the thin film is all gone.
(Arctic Silver also makes a liquid solution for this that works equally as well.) This does take quite
a bit of time and several passes to remove that “film”. Keep it wet and take your time.

The last mini I re-pasted… I had to actually pry up on the four corners of the heatsink to remove
it AFTER the pins were removed. I’d say that it was really BAKED on. When it did come loose, the
clear mylar normally surrounding the chip came off with the heatsink. I did not replace that. I just
cleaned everything up & re-pasted with Arctic Silver and that 1.42 GHz mini has been fine since.

    *

After cleaning the above (and also below), I apply new paste and replace the heatsink and pins.
Bet there are a lot of people that have never seen this view…

   *

*After applying the paste, twist the heatsink a bit, back and forth with light downward pressure
in an attempt to equally distribute the paste before pushing the retainer pins through the mobo.

FIN

Have sorta covered this a bit before:
http://macos9lives.com/smforum/index.php/topic,4925.msg35560.html#msg35560
(Better pictures & more info now.) *Make sure you put your fan back in correctly after teardown.

AND more info on G4 Mac mini exhaust HEAT and bottom heat, etc… found in this post and entire thread:
http://macos9lives.com/smforum/index.php/topic,5955.msg52638.html#msg52638

OH... and if you poke a hole in any of that tape to remove your original HD screws (either for fun or to replace the HD with an SSD) cover that back up or replace it with another piece of tape - so the fan doesn't possibly blow / bleed any hot air back into the interior as it exits the mini through that hole. ;)

ssp3:
Very useful. Thank you!  :)

What did Apple use originally? A thin thermal pad or thermal paste?

FBz:
You’re most welcome.

Was thinking of your recently deceased mini and wondering about the status of C573, C567, C447 and C452 on your mobo and whether or not one (or more) of them may have “removed themselves” under prolonged or sustained heat? I’ve a 1.25 MHz model here that someone sent to me DOA and I just noticed C573 and C447 were absent today. Hmmm?

Check them devils, ehh?

And I wouldn't call it a paste... it was more like a very, very (paper thin) pad. Like a thin paper sheet. You'll see it when you get your heatsink off, if it had never been removed and pasted before.

DieHard:
I predict this will be a "must read" for mini owners so it's getting the biggest sticky (bold listing) it can get :)

ssp3:

--- Quote from: FBz on October 19, 2023, 05:55:11 PM ---OH... and if you poke a hole in any of that tape to remove your original HD screws (either for fun or to replace the HD with an SSD) cover that back up or replace it with another piece of tape - so the fan doesn't possibly blow / bleed any hot air back into the interior as it exits the mini through that hole. ;)

--- End quote ---

BTW, that is explicitly mentioned in the Service Manual.




If you're going to use "naked" SSDs or adapter boards, cover this hole too.



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