Apple Macintosh

Power PC Late 2004 Rev. B. Dual 2Ghz CPU

PARTIAL DISASSEMBLY GUIDE.

by MIKX September 2006

All photos ©

Do not use this guide for liquid cooled G5's

This guide does not take you to the point where the motherboard can be removed.

We will just be removing the CPU-Heatsink Units and the Power Supply.

(The author assumes no liability nor responsibility for any damage incurred by anyone using this guide)

- PREFACE -

Now that the G5 was in the spotlight I decided to look at this Mac's operating and ambient temperatures using Marcel Bresink's excellent "Hardware Monitor" and was shocked to see that the Memory Controller Heatsink was running at an average of 72°C, that is too hot for my liking, especially in a humid country like Japan where I live. To make a long story short, the Memory Controller Heatsink - after partially disassembling my G5, cleaning and removing huge amounts of dust now averages 57.5°C. This is a reduction of 14.5°C !

All other sensor readings are dramatically reduced. To achieve this I had to overcome an irrational and deeply rooted, conditioned fear of touching things that Apple doesn't want me to. Endless checking around the internet yielded only one relevant page put up by the very courageous Carl Otto.

His G5 disassembly page is HERE and he very kindly replied to my emails with advice and help for which I am eternally grateful.

I have some little experience with tearing computers apart and rebuilding them, I have owned many Amiga and Mac models. FDrom swicthing off my G5 - disassembling - dust removal-cleaning -re-assembly and restart took about two hours. If you have ever upgraded a CPU in older G3 or G4 Macs you will not come to grief if you plan the disassembly like a military operation. Work slowly, thoroughly, keep notes, check everything three times.

Assemble the tools and prepare your workspace thoughtfully and soon enough your G5 will be clean, cool and happy.

MIKX

Tools Required

Two cans of compressed air / a fine brush for dust removal / plastic tweezers.

2.5mm Allen Key : The total length of this tool NOT including the handle must be a minimum of 15cm.

Allen key size2.5mm (The handle width should not exceed 13mm).

If you can't find the exact one, modify an existing one.

First Steps to G5 Disassembly

(PRINT THESE STEPS OUT)

Pic 1.

1. Shutdown your G5 - remove the power cord, monitor cable and any external Audio/USB/Firewire cables.

2. Place the G5 case on a clean wide table with good lighting - remove the aluminium door - the clear plastic airflow door - all memory DIMMS and the CPU Fan assembly.

3. Ensure that you have 2 Phillips head screw drivers, one large and one little and a box (with a lid) into which you can put the various screws that we will be removing.

4. This step is not strictly necessary but just good common sense : - Remove all third party PCI cards, including your graphics card (won't hurt to clean the card).

5. Now it is time to remove the CPU Cover (pic 1.)

The CPU cover has a small, grey two part locking pin in one hole on the top of the cover (Pic 2. ). Pic 2.

This pin is a pain to remove - the trick is to use a very fine pointed object to pry up the centre of the pin - not all the way out - just out enough to "unlock" the pin.

having slid the centre part up, lever the whole pin out.This pin is not a crucial part, you could fabricate another later.

6. Remove the CPU cover by sliding to the front of the G5 case and up.

7. Remove the front CPU COVER FRAME (Pic 1.) by gently pulling up and to the front of the case. This part has lugs that seat into holes in the two CPU heatsinks.

Pic3.

NOTE : Now you can see the two CPU-Heatsink units - It is crucial that you mark each with a pencil "A" & "B"

make corresponding marks on the nearest case edge.Each unit MUST go back in the same position as one is a master

and the other a slave. Mix it up and your fans will go crazy and speed will be reduced.

Pic 4.

8. The CPU Heatsink Allen screws. (NOTE: The posts into which the Allen Key screws sit are called "LAGSHIELDS" see pic 10).

Now here is where you will be using the special Allen key tool. I stress that it's dimensions are crucial to undoing the screws

( NOTE : These Allen screws can be left in place in their holders ). The Allen Key Tool should be 15cm in length with the handle being no more than 13mm in width.

8.1 Now you will need a small torch to help you see the Allen screws in their holes - using the Allen key tool, loosen each one - don't remove them.

9. Removing the CPU-Heatsink units:

Once you are certain that all Allen screws are loose you may remove the CPU-Heatsink units. Lift each, slowly, straight up - lifting at an angle could damage the CPU connector.

Pic 5.

Place them on clean paper in the order they were in the case - they need to go back to the exact same positions later.

Pic 6.

10. Removing the REAR CPU FANS & REAR GRILL & gasket

The Rear CPU Fans are easy to remove, just press down on the two tabs that hold them in place - they can now be moved to one side OR removed completely for cleaning if you remove their power cable - GENTLY.

Behind the Rear CPU Fans there is the airflow exit area frame and infront of that, flush against the inside rear of the case, a gasket. This gasket is held in with about 8 fine screws, you will need a fine Phillips head driver to remove them. NOTE THE ALIGNMENT OF THE GASKET for later replacement. Remove the gasket.

Pic 7 . Pic 8.

11. Removing the Power Supply cover - this covers the Power Supply Unit (PSU).

There are two large screws in the Power Supply Cover: Remove them with your large Phillips Head driver.

Now remove the LOWER "lagshields" ( the post pins into which the CPU-Heatsink Allen screws are seated) to allow the Power Supply Cover clearance for removal.

12. Disconnect the THREE Power Supply connectors : This is done by PRESSING gently on the levers on the connectors and also gently pulling.

13. Now carefully & slowly remove the Power Supply cover.

Pic 9.

12. Removing the Power Supply (PSU).

There are four (4) large Phillips head screws on the bottom exterior surface of the G5 case. At this point I suggest asking someone

to steady the G5 case at an angle that will give you sufficient clearance to allow you to remove these four (4) screws.

Having removed the screws you are now free to remove the Power Supply Unit (PSU) - slide it gently to the front of the G5 case and then even more gently, up and out of the case.

Congratulations! You have completed this major operation. Proceed with taking the PSU apart for cleaning - don't touch anything inside it,

use compressed air & brushes!. Do the same with all of the parts you have removed so far.

PUTTING EVERYTHING BACK IN THE CASE

Carefully replace everything in the reverse order to which you removed them . . . .

read the notes below when you come to replacing the CPU-HEATSINK UNITS.

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Pic 10 .

REPLACING THE CPU-HEATSINK UNITS - NOTE 1

The most important element in putting eveything back is ensuring that all of the LAGSHIELDS (the posts into which the Allen Screws sit) are sufficiently tight (just a bit over "finger tight"). The object is to secure the CPU-Heatsink Units securely to restrict movement.

If you find a loose LAGSHIELD you can insert a fine screw driver shaft into the holes in the sides and "gently" tighten them.

I cannot stress too much that too much tightening will lead to big problems.

REPLACING THE CPU-HEATSINK UNITS - NOTE 2

Prior to replacing the CPU-Heatsink Units the Allen Screws should just sit "loose" in the LAGSHIELDS until you are ready to secure the CPU-Heatsink Units.

Replace CPU-Heatsink Unit "A" (closest to the PCI slots) gently; the unit will 'click' into place.

Do the same with CPU-Heatsink "B".

Now begin evenly tightening all of the Allen Screws with your special Allen Key tool.

DOUBLE CHECK THAT EVERY ALLEN SCREW IS IN PLACE AND TIGHTENED.

Proceed, methodically, thoroughly - there should be no screws left over.

When re-installing cables - put the G5 power cable in LAST.

DUST is your enemy. It clogs air intakes, gathers on fan blades and reduces their efficiency.

Dust will eventually raise the ambient temperature inside your G5 case. Your G5 will shut down rather than allow a CPU to be damaged.

While looking at the following pictures bear in mind that prior to taking them I had already removed 80% of the obvious dust clumps that were visible in the case.

The first three pics are scary

Below :

A single clump removed from the interior of the PSU.About 10cm in length.

Below :

To show scale, a clump removed from the general bottom area of the G5 case UNDER the usually inaccessible area under the PSU cover.

The bottom case area with 80% of the dust removed.

Here is how the PSU "SHOULD" look . ..

This guide is intended for owners of late 2004 Revision B. dual processor 2Ghz PPC G5's.

If you have one of these G5's and it is out of warranty and not in Apple Care and you have some experience in pulling computers apart . .and putting them back together . .successfully . .then perhaps this guide will be useful for any repairs / replacements that need to be done in inaccessible areas in the case.

Have fun.

MIKX - JAPAN.

( There is no clickable link to my mail address to avoid spambot mail address harvesting, please type in manually )

Do not use this guide for liquid cooled G5's