My observations on reapplying thermal paste on a Powerbook G4

Discussion in 'PowerPC Macs' started by Tito910, Jul 12, 2016.

  1. Tito910 macrumors member

    Joined:
    Jul 10, 2016
    #1
    Short version: not worth it.
    ---
    So I'm the proud owner of a Powerbook G4 12 inch. I bought it mostly-mint and I love it. I surprisingly am able to actually use it for daily work which is impressive considering it's over 10 years old! I'm typing this thread on it. Anyway, while I'm fairly happy with the thermal output on it, I wondered if I could do better by applying new thermal paste. I've heard some accounts of 8c drop in temps and some others with no drop at all. So I decided to give it a go.

    First the specs:
    12 inch Powerbook G4 Aluminum
    1.5ghz 1.25gb ram SSD
    Arctic Silver MX-4 thermal paste

    I measured temps before and after and took some pictures. I ran both before and after tests in a room with 73F ambient temp using a Flash youtube video playing in full screen. I let it go for 20 minutes then checked the cpu and gpu temps using Temperature Monitor.

    Before: cpu: 61.5c -- gpu: 58.5c

    I followed the guide and removed the heatsink. Several things stood out to me. First the thick thermal pads and then the exposed heatpipes

    [​IMG]
    ^The heatsink covers 3 chips. From the top: the g4, a very large Agere chip (southbridge?), and the nvidia gpu. The bottom two have a thick reusuable thermal pad. The G4 had something else on it though. My best guess is some sort of phase change material. It was a pain to remove.

    [​IMG]
    ^Here's a shot with the pads removed. You can clearly see the exposed heatpipes. This is less than ideal as it allows massive air pockets between the thermal pad and the heatsink.

    [​IMG]
    ^ here's a shot of the chips without the heatsink. The g4 is on top, then an Agere chip (aka big-chip), and last the nvidia gpu. It looks like the vram is stacked on top of the gpu in a package-on-package config.

    [​IMG]
    ^a shiny and clean G4!

    So my original plan was to apply thermal paste on all 3 chips. However after opening up the heatsink I had to change my plan for several reasons. First the exposed heatpipes would mean I would need to use a lot of thermal paste to remove the air bubbles. Second, the nvidia gpu was partially covered by the laptop's internal frame. If I had to reapply thermal paste it would be very difficult to clean up the gpu without having to remove the entire frame. And most importantly, the frame forced a gap between the heatsink and the big-chip and gpu. This isn't an issue for a thermal pad since it's thick enough to easily bridge the two. But a thermal paste is only supposed to be a thin spread. It's not meant to fill 1.5 mm gaps!

    The G4 made direct chip to heatsink contact, so I used thermal paste on there. But I refitted the big-chip and gpu thermal pads. I closed everything back up and ran my test again.

    Before: cpu: 61.5c -- gpu: 58.5c
    After: CPU: 61.0c -- GPU: 58.2

    I suppose they are lower. But they're so close they might as well be the same.

    All in all I'm a bit disappointed by the cooling system of the G4 Powerbook 12 inch. 1.5 mm thermal pads and exposed heatpipes that create huge air pockets! But even then it's a huge step up from my 15 inch tibook.

    While it was cool to take a peak inside the machine, there was virtually no movement in temps and you run a risk of causing serious damage to the computer. I wouldn't recommend doing this.
     
  2. eyoungren macrumors P6

    eyoungren

    Joined:
    Aug 31, 2011
    Location:
    Phoenix • 85037
    #2
    My wife has the 1.0Ghz 12" PowerBook. Got it for $58 and a new screen for about $20 which was all it needed (it rolled down a flight of stairs at a house in New York city).

    The process of swapping the screens meant it had to be taken completely apart. With all the tight tolerances in there I broke the sleep light cable and a keyboard key. At one point a hacksaw was involved when I ran a long screw back in the wrong place.

    By the third time of taking it apart I got things working fine. I left the heat sink off the first and second time because I had broken the springs on the spring screws over the CPU. Consistent thermal shutdown demanded I had to open it up a third time to put the heatsink back (I had to open it a second time because I hadn't gotten the logicboard connected back correctly).

    By the time replacement parts arrived I opened the damn thing a fourth time and it's been closed since then because I don't want to open the damn thing ever again!

    I did not do any repasting because at the time I was very unfamiliar with that. But despite everything (as well as a fall which dented a corner (my wife)) the Mac still functions perfectly without overheating.

    So, I am in agreement with your experience that repasting, at least with this model, probably doesn't help much.
     
  3. HansiS macrumors newbie

    Joined:
    Dec 8, 2014
    #3
    I'm feeling that my 12" PB lately is getting kinda hot and noisy (as in more than usual) and I was considering to change and reapply the thermal paste as well. It's still the same as it was twelve years before. Too bad your experiences show no improvement.

    But on the other hand, I opened and tinkered it many times and the thought of going through yet another full tear-down feels unjustifiably.
     
  4. Dronecatcher macrumors 68000

    Dronecatcher

    Joined:
    Jun 17, 2014
    Location:
    Lincolnshire, UK
    #4
    I bought a 1Ghz 12" Powerbook when they were first released - I don't ever recall the fan being noisy - are the lower speed variants noisy now I wonder?
    I currently have a 1.33 Powerbook and a 1.33 iBook - I love the form factor of the Powerbook but hardly ever use it, as the slightest thing brings the fan on and anything taxing makes it stupid loud. You'd have thought all that metal would have worked wonders for heat dissipation - by contrast the iBook is always silent.
     
  5. 128keaton macrumors 68020

    128keaton

    Joined:
    Jan 13, 2013
    #5
    I think, more often than not, on these 12" the bearings dry up. A quick bit of oil for me always quietens it.
     
  6. bobesch macrumors 6502a

    bobesch

    Joined:
    Oct 21, 2015
    Location:
    Kiel, Germany
    #6
    You may use G4FanControl to fall in love with the PowerBook...
     
  7. eyoungren macrumors P6

    eyoungren

    Joined:
    Aug 31, 2011
    Location:
    Phoenix • 85037
    #7
    Doesn't work on the 17" PowerBooks. :D

    God knows I tried. And the dev was completely unresponsive when I emailed/contacted him.
     
  8. bobesch, Jul 14, 2016
    Last edited: Jul 14, 2016

    bobesch macrumors 6502a

    bobesch

    Joined:
    Oct 21, 2015
    Location:
    Kiel, Germany
    #8
    Thank you so much for that excellent foto-documentation!
    It'll help others to feel more comfortable to open the Book for regoofing.
    I broke one of the spring-attached screws off the logic-board, when I did the same you did (kinda screwed up the book...) - maybe it was broken before. I was lucky my friend&neighbour soldered it onto the board again without damaging anything...
    --- Post Merged, Jul 14, 2016 ---
    If you run your book with a CCC/SuperDuper! copy from another book with different specs G4FanControll might not work. A fresh install could help.
     
  9. 128keaton macrumors 68020

    128keaton

    Joined:
    Jan 13, 2013
    #9
    Oh yeah. Mine was loud and annoying too, but it wasn't that hot. G4FanControl fixed that riiiight up
     
  10. crammedberry macrumors regular

    crammedberry

    Joined:
    Jan 5, 2011
    Location:
    The Golden State
    #10
    It's pretty surprising that you didn't see any significant results from reapplying thermal paste. I did this to my iMac G4 and it actually made it run cooler. I don't recall if they have CPU temp sensors, I did this a few years ago but I recall it running cooler without the fans blasting all the time.

    I also reapplied thermal paste on my old MacBook Pro, one of the few still alive with the 8600m Nvidia cards, and the temp on that one dropped by 10ºC after reapplying.
     

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