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

[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.

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]

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.

BTW, that is explicitly mentioned in the Service Manual.




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

[FBz]

While we’re at it…  we don’t have a copy of the G4 Mac Mini Service Manual
in the Apple Repair Manuals & Reference Materials (in the Download Boards section).

But for those interested:
https://www.applerepairmanuals.com/the_manuals_are_in_here/mac_mini_sm.pdf

And odd, there’s no mention whatsoever of how to remove & re-paste the CPU heatsink. 

[ssp3]

FYI. There are two versions of Mac Mini G4 service manuals - from 2005 and from 2006.
2006 version is about those silent upgrade Minis.

[DieHard]

While we’re at it…  we don’t have a copy of the G4 Mac Mini Service Manual
in the Apple Repair Manuals & Reference Materials (in the Download Boards section).

Yeah... that download board was put together when the mini was OS X only and quite use-less, it's amazing that a machine that is such a "dog" under OS X with 1 GB Max, is now so beloved under OS 9.

Lastly, I remove the punctured tape use black electric tape after upgrading the HD to keep the air flow (since the old tape if removed does not stick well), I also use a small square of electric tape on the end of the cardboard channel to keep it in the correct shape and venting air.

[ssp3]

This short guide is worth reading. It is a website of electronic components supplier, not some boutique cooling products manufacturer pushing their overpriced warez.

https://uk.rs-online.com/web/content/discovery/ideas-and-advice/thermal-interface-materials-guide

One interesting line from that guide 

There is only likely to be approximately half a degree difference between using thermal pads or thermal paste in most standard applications.

Question. How many of users here had CPU overheating problems with their Minis that were in their original condition, not re-pasted by previous owner? Raise your hand.

[smilesdavis]

„ Bet there are a lot of people that have never seen this view…

I have in my G3bw ive just restored and cleaned

I still dont know whats that square piece of tape for or whats it called

I just cleaned it with ipa and applied new thermal grease and that was it

[FBz]

For those possibly hemostat-challenged  or caffeine-jittered  among us…

Two other very low-cost approaches to compressing those “winged” spring rivet fasteners (“push pins”) on your G4 Mac mini. One uses a nylon spacer… while the other, a more expensive, brass tube. I prefer the nylon spacer.

And I LOVE Ace Hardware stores!

   

Once the above-noted nylon spacer is pressed down firmly upon the “wings” and flush with the mobo, you can either use the pin to push the fastener on through the mobo - OR even use a 6 or 7d smooth finished nail (with the point cut or ground off). You could possibly even leave the point of the nail on if you’re dangerous.

   

Actually, once the nylon spacer is pressed down firmly and then ever-so-slightly  wiggled, the wings often will snap down within the mobo and you can then press them on through the mobo to release the heatsink (with whatever your little heart desires / pointy or not). Carefully.

    *

The brass tubing option is a bit more costly. $1.99 plus tax for a 12” length. [K&S Precision Metals #8128 5/32 O.D. x .014 I.D.] This fits over the wings a bit more snug and I’d most definitely recommend using a tiny bit of white lithium grease (or other light lubricant) to aid in the fitting / removal. Clean it up afterwards. And you may still need to use the pin noted above, or nail, etc. And of course, you’ll need to cut it to a usable length.

NOTE: The bigger-headed fasteners pictured are from a G5 iMac. Don’t know if their heads are too large for the mini’s heatsink - but their length and “wings” are very nearly the same. (G5's are just a bit longer.) And I should’ve shown one of the pins placed inside of a nylon spacer but hopefully that bit’s understood.

If none of this makes any sense to you… read this entire thread from the beginning.

[sonicsky]

I bought the pin in taobao china, the size is ok, anyone can contact me, [email protected]

[joeykork]

in case anyone knocked off C447 like I did when removing the heat sink rivets on my 1.25Ghz, I measured it as 9391pF (~0.01uF) on my ESR meter.

[fergycool]

Many thanks for this. I'd already got my 1.5Ghz G4 Mac Mini up and running, but I was a little scared at removing those pegs. But I just went back in and it went pretty well. It was seriously caked solid and I had to soak the heatsink in white spirit for an hour. But once cleaned up then with a bit of Noctua's NT-H1 3.5g paste, it was soon back up and running!
I used some forceps (taken from my fishing box!). But I did try a solder removing tool. That has a tube that fitted nicely over the top of the peg. Unfortunately I had no way to push the peg out. However, once I'd reassembled the Mac, then I remembered that if you push the plunger in the tool it does extend a little rod that would likely have worked. Just a thought for somebody to try (..or me if I get a second G4!). Thanks

[ssp3]

The nozzle of that desoldering tool is made of teflon, which is softer plastic than the one used for heatsink pegs, so it is now damaged.
Judging by the distance the plunger extends from the nozzle and that its not centered, I'd say that your tool is in pretty bad shape. Don't use it on delicate boards, like Mini, because it will scratch them, when you fire it. The effect (movement) is similar to the recoil of the gun - that metal part shoots towards the board.

[fergycool]

Aha! Whoops! I never thought about the hardenss of the nozzle. I did not actually use this though, just tried it.

[aBc]

Kudos for the original thought of possibly using the desolder tool. Maybe removal of the teflon tip, replaced with a similar length of the nylon spacer stock (mentioned above) in its’ place, might then work as a pin removal tool?

I really don’t use the desolder pump that I have due to the “shocking” recoil of the thing when working on very small bits. (It’s quite unnerving to me, working so closely and with magnifying headgear on - so I revert to using solder wick instead.)

And I mean, that when you “fire” such desoldering pumps they don’t extend (shoot) that metal plunger out of the end “towards the board”. That’s only extended when you elect to push the “un-cocked” plunger down through the nozzle to clear any hardened solder out of that nozzle. So if the nylon stock could be cut & fitted instead, one might actually have their own special Mac Mini heatsink removal tool?

Well, worth a shot anyway. There’s a project for someone. (You did put the hemostats/forceps back into your fishing tackle box?)

Looks like the processors’ mylar shield stuck to your heatsink (as if often the case). I usually remove that and don’t even attempt to reuse it. Also I peel the original thin foil off on the heatsink, which I assume originally served as a “paste-treated” barrier between the processor and the heatsink.


And looking at the red-outlined area, the white-ish looking areas are where the thing remained “stuck” to the processor (green dots). While the smoother, dark grey areas (yellow dot) might represent where actual heat-exchange contact was no longer in effect. (i.e. baked and separated.)

So whereas most recommend replacing heatsink paste every two-to-four years... some have G4 Mac minis that have never had this done (now, in nearly twenty years!).

Again, it would have been interesting to note the exhaust air temperature of your mini before replacing the paste. But big congrats on a job that many simply choose not to attempt!

[ssp3]

And I mean, that when you “fire” such desoldering pumps they don’t extend (shoot) that metal plunger out of the end “towards the board”. That’s only extended when you elect to push the “un-cocked” plunger down through the nozzle to clear any hardened solder out of that nozzle.

I should have added "when the nozzle is worned out".
When you use the pump extensively, the nozzle wears out rather quickly. From inside too, btw. Or, when you push the solder out or try to pull the plunger in by force, when some of the solder is stuck to it, it is possible to displace the nozzle a tiny little bit. As soon as plunger's tip is not flush with the nozzle's tip, your PCB is in danger. I've used up more than 20 pumps and even more nozzles to this day, so I know what I'm talking about. And I've scratched a few PCBs too

(I do have Hakko station and other desoldering tools, in case you're wondering, but that's another story).

A few pics from the web below.

[fergycool]

And looking at the red-outlined area, the white-ish looking areas are where the thing remained “stuck” to the processor (green dots). While the smoother, dark grey areas (yellow dot) might represent where actual heat-exchange contact was no longer in effect. (i.e. baked and separated.)

I removed everything and very carefullly also tried to clean the top of the CPU (although not too hard!).

Again, it would have been interesting to note the exhaust air temperature of your mini before replacing the paste. But big congrats on a job that many simply choose not to attempt!

Thanks. The exhaust air temperature was not too hot before, although I this was just tested with a wet finger rather than a thermometer. Now you can barely feel any heat at all.

Forceps are in my computer tool box now. There's two other pairs in my fishing box anyway :-)

Thanks again.