Introduction
The Power Mac G4 MDD Uses two system fans, an optical fan (for the optical drives), and a main system fan (cools the CPU, the hard drives, and the graphics card).
What you need
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            The Power Mac G4 MDD: the last, and the fastest G4-based Mac. This computer boasted up to a Dual 1.42GHz PowerPC G4 CPU (though I have a single 1.25GHz). 
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            Six USB ports. 
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            Four FireWire ports. 
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            Assorted SCSI (SCSI50/SCSI68) 
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            Assorted Audio 
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            Video (ADC & DVI) 
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            Networking (RJ-45 Ethernet/56k Modem) 
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            Some later model MDD's (such as the dual 1.42GHz) Have a FireWire 800 Port Here: 
 
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            It's likely that there is a cable clip holding the ribbon cable to the case. 
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            To remove it, push the end, and it should pop up. 
 
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            With the clip free, pull on this tab, lift the cage up, until it clicks, and pull it away. 
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            Now, set the cage on top of the CPU, and remove the power connectors. 
 
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            Once the cables are free, set the drive cage aside. 
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            To remove the hard drives from the cages, remove the four screws on the sides of the cage that are connected to the drives, than slide the drives out. 
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            The two cages are cross compatible and can be put in either rack. 
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            The MDD does not have a 128GB drive limit like older macs, My MDD has 3 Drives (A 400GB Hitatchi Deskstar, 40GB Seagate Baracuda 7200.7, and a 30GB Quantum Fireball LCT). 
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            Note the ID jumpers on the two drive set. One is set to Master, the other to slave. A single drive can be set to Cable Select. 
 
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            Remove these two Phillips screws: 
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            Now, pull the cage away from the front until it is free. 
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            Now, lift the cage out. 
 
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            To remove the drive from the cage, remove the four screws on the side of the drive, and pull the drive out of the cage. 
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            My MDD has a 3rd Party 22X SuperDrive, for burning DVD's in Leopard (Thank You Generic Drive Support!) 
 
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            Optical Fan: 
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            Remove these two Phillips screws: 
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            Now, slide the plate towards the case, and lift it up, and off. 
 
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            Once the cover is removed, disconnect the power cable and thread it under the dust shield. 
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            Now, lift the fan straight up and out. 
 
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            System Fan: 
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            Disconnect the optical drive IDE cable from the logic board. 
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            Now, remove the system fan cable. 
 
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            Now, grab the system fan by the sides and pull it up, it should come free, the system fan is very large and loud, compared to standard sized fans. 
 
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To reassemble your device, follow these instructions in reverse order.
To reassemble your device, follow these instructions in reverse order.
