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MDD to ATX Case ConversionReturn to News Page

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Apple Mirror Drive Door to PC ATX Case Conversion
By W. Li
Posted: 8/8/2005


Author's Disclaimer: This project will void your warranty. There is a fair amount of sheet metal work involved. This is presented for interest only and is NOT an apple approved modification.

Introduction
As delivered, the 2002 G4 towers are a marvel of case design. Incredible functionality is crammed into a rather small stylish case with little room to spare. The stock case is made up of two parts: the multiple exterior stylish plastic plates, and an inner very rigid steel chassis. One big feature is the swing out door to expose the entire motherboard. (This is also true of previous towers since the 1999 B&W G3 Model) The rivets that secure the hinge of the fold-out side access door to the main chassis will be removed. There is much cabling under the motherboard that must be disconnected very carefully as much of it will be re-used. The usual caveats apply in handling the motherboard. This project involves few electrical modifications, and a fair amount of sheet metal work.

My primary goal in this project was to improve internal cooling. Common complaints of the stock configuration are a lack of adequate cooling when fully packed, and really loud fans.

The New Case
Generic PC cases are attractive for these projects as they are plentiful, and the cost is low. I selected a new ATX midtower from Directron.com: the all aluminum SF-561S for $42. It has five exposed 5.25in and three 3.5in exposed bays, and four internal 3.5in bays, as well as capacity two front and one side 80mm case fans. There is no motherboard pullout plate. Here is the interior of the new case. (Fig 1)

Pix of ATX case
Figure 1: An interior view of the new case as delivered


Disassembly of the Stock Computer
First, remove all the exterior plastic plates and handles from the Apple MDD case. You'll need a small hex tool. Next, remove all the stock subassemblies and the drives with their cables. Remove all fans and the power supply. You will essentially strip out everything from the stock case. Detach all cabling to the motherboard. Remove the large heatsink and the CPU daughter card. Store everything in static-proof bags. The motherboard is held in by just ONE screw to the hinged steel swing out door. All the other motherboard supports are obtained through small steel flanges. Remove the motherboard and store it in a static-proof bag. The hinge is a robust piano hinge that is riveted to the main chassis. I left the hinge attached to the swing out steel door, by drilling only those rivets that attatch it to the main chassis. (Fig 2).

stripped MDD mb tray
Figure 2: Here is the isolated steel door that held the motherboard

None of the remainder of the stock case is reused in this project.

Note that the rear vertical steel plate containing the port cutouts is left attached to the MB chassis. (Fig 3)

ATX case MB tray
Figure 3: Another view of the steel MB chassis showing the
rear port plate with all the plastic removed


New Case Modifications
The stock MB chassis was then placed inside the new case, noting that nothing matched up with any of the rear ATX cutouts. I carefully marked where the discrepancies were on the ATX case, and cut the rear aluminum on the new case to just clear the rear stock steel chassis. Remaining holes were covered with thin aluminum perforated sheet. as seen here. This must be done carefully and precisely as this step is irreversible.

In this manner I was able to preserve the excellent rigidity of Apple's steel motherboard chassis and also have a ready-made rear port plate. Note that all the rear slots are recessed in the new case, as they were in the original case. Note also the squarish cutout for the power supply AC plug at the top of the case. This one step saved me all the headache of attempting to create a sturdy motherboard mount in the new case. (Fig 4)

rear case pix
Figure 4: A rear view of the new case showing case cutouts


You have to cut out a portion of the upper right corner of the MB plate to clear the 5.25in drive bays in the new case. This cut has to be measured carefully to just clear the bay support cage and yet not impinge on the motherboard once it is mounted. (Fig 5)

ATX case internals
Figure 5: Stock steel MB plate bolted to the case


I now bolted the hinge of the MB plate to secure it to the new case along the lower edge, and bolted the steel plate away from the MB along the upper edge . The rear port plate abuts against the rear of the new case. And here is the same view with the motherboard mounted (Fig 6). You have to drill these bolt holes in the new case chassis.

ATX internals w/MDD MB
Figure 6: Motherboard mounted on its steel chassis inside the new case

Note the CPU connector ready to receive the CPU daughter card in lower left of the image. I used the same mounting hardware for the daughter card and its heatsink. This was possible only because the stock mounting plate was re-used.


Power Supply
These models employ a non-ATX form factor power supply. The stock power supply does not have the square form factor that the ATX cases are built for. These are long thinner supplies. However, it will fit nicely at the very top of the new case. Its width is just 2mm smaller than the lateral internal sheet metal of the new case. It is held in place with a wooden shelf, secured to the new case with screws. The hex screw at the rear of the supply is reused to secure it to the new case to prevent for-aft motion. The rear of the stock power supply case was cut to allow less air resistance. (Fig 7)

PS Cutouts
Figure 7: Some metal was removed from the rear of the cage to improve air flow


The top 5.25 inch bay of the new case is dedicated to a custom intake duct for the power supply; mounted onto a 5.25" to 3.5" adapter plate. In this way, I was able to isolate the power supply cooling airflow by drawing outside air through a front grill. (Additional cooling of the power supply is possible by opening up the top of the stock supply case, and adding a top exhaust fan). The existing supply leads reach the power input connector on the motherboard except for four leads, which were merely spliced an inch longer.

The stock power supply 60mm fans are a well known source of noise. I removed both stock Delta 38CFM 47dBA sleeve fans and mounted two new Evercool ballbearing 26CFM 30dBA fans. Side-by-side they do not fit inside the supply cage, but do bolt in if mounted outside. The cover space left by the old fans of the supply was later closed off. (Fig 8).

PS Fans
Figure 8: New Evercool fans mounted on power supply


Components
The hard part is over! Using the stock mounting hardware, I installed the CPU daughtercard, then the huge aluminum heat sink; mounting its 120mm fan on a small aluminum bracket screwed into the two tapped holes on the sink. I did not re-use the noisy 120mm 150CFM 153dBA Delta fan, but instead installed a Panaflo 115CFM 45dBA high efficiency fan. A small cardboard square directs exhaust flow of this fan directly over the heat-sink and out the back grill. It is cut in such a way that it fits snugly against the rear of the case, as well as the side panel once that is installed. I tried to keep the warmed heatsink fin air out of the case. (Fig 9)

Final internals pix
Figure 9: Interior view of the completed project


Speaker
The Apple speaker was clamped to the rear of the three bay 3.5in housing as shown above, and a simple perforated aluminum grill attached in front. It is rarely in use, as audio is usually taken out the rear audio port.

Front Power Control
The front power control box was left intact, and was mounted behind a 5.25" cover plate with the LED facing forwards. The LED illuminated a small plastic pilot lamp bezel press-fitted to a 5.25" cover plate. I soldered two small wires from the Apple microswitch to the front case power button microswitch.

Here is the finished product. The power supply intake duct grill is on top, the power control panel LED below, an empty 5.25 inch bay for future expansion, a Superdrive, and a Zip 100 drive. The speaker grill is below, and two 80mm case intake fans are at the bottom to cool the internal hard-drives. The front USB and Firewire ports are not connected, and remain a future project should the need arise. (Fig 10)

Finished front case pix
Figure 10: Front case view


Operating temperatures
I tested using OS 10.39 and Thermograph X, as well as external thermocouples mounted inside the power supply and in the fins of the CPU heat-sink. With a room temperature of 75°F the CPU temperatures dropped from 145° to 123°F in spite of a lower capacity fan. The power supply probe read 92°F and the CPU fin probe read 102°F. Both hard-drives ran at 90°F. Clearly, installing lower airflow but quieter fans did not compromise internal operating temperatures.

Summary
All in all this was a very satisfying project. It took better part of a week, most of which was spent in getting Apple's steel motherboard plate to fit inside the new case in a secure and useful manner.
W. Li
Mercer Island, WA


Other System/Case Conversion Articles:
For other System/Case Conversions, Cooling mods, and related articles, see the Systems page (organized by mac model/series).
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