Power Mac G4 MDD Power Supply Replacement

  • Author: Chris Green
  • Time estimate: 30 minutes - 1 hour
  • Difficulty: Difficult

The Power Mac G4 MDD Used a uniquely shaped 344W or 400W AcBel or Samsung Power Supply. It had a 24-Pin Connector (not 24-Pin ATX!) and the original AcBel power supplies were notoriously loud, and earned the Power Mac G4 MDD the nickname "WindTunnel," since the computers were so loud.

Edit Step 1 Case  ¶ 

Image 1/2: Six USB ports.

Edit Step 1 Case  ¶ 

  • 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).

  • Six USB ports.

  • Four FireWire ports.

  • Assorted SCSI (SCSI50/SCSI68)

  • Assorted Audio

  • Video (ADC & DVI)

  • Networking (RJ-45 Ethernet/56k Modem)

  • Some later model MDD's (such as the dual 1.42GHz) Have a FireWire 800 Port Here:

Edit Step 2  ¶ 

Image 1/3:

Edit Step 2  ¶ 

  • Pull on the side lever and lower the side of the case.

Edit Step 3 Hard Drives  ¶ 

Image 1/1:

Edit Step 3 Hard Drives  ¶ 

  • The hard drive cages are located here.

Edit Step 4  ¶ 

Image 1/3: Start by removing this screw.

Edit Step 4  ¶ 

  • Cage 1

  • Start by removing this screw.

  • Remove the IDE ribbon cable from the motherboard.

Edit Step 5  ¶ 

Image 1/2:

Edit Step 5  ¶ 

  • Now, remove the power connecton from the drives.

Edit Step 6  ¶ 

Image 1/3: Now, you can set cage 1 aside.

Edit Step 6  ¶ 

  • Now, push this tab down, and pull the cage towared you.

  • Now, you can set cage 1 aside.

Edit Step 7  ¶ 

Image 1/2: Remove this Phillips screw:

Edit Step 7  ¶ 

  • Cage 2:

  • Remove this Phillips screw:

  • Disconnect this IDE ribbon cable from the logic board.

Edit Step 8  ¶ 

Image 1/2: To remove it, push the end, and it should pop up.

Edit Step 8  ¶ 

  • It's likely that there is a cable clip holding the ribbon cable to the case.

  • To remove it, push the end, and it should pop up.

Edit Step 9  ¶ 

Image 1/3: Now, set the cage on top of the CPU, and remove the power connectors.

Edit Step 9  ¶ 

  • With the clip free, pull on this tab, lift the cage up, until it clicks, and pull it away.

  • Now, set the cage on top of the CPU, and remove the power connectors.

Edit Step 10  ¶ 

Image 1/2: 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.

Edit Step 10  ¶ 

  • Once the cables are free, set the drive cage aside.

  • 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.

  • The two cages are cross compatible and can be put in either rack.

  • 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).

  • 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.

Edit Step 11 Optical Drive Cage  ¶ 

Image 1/2:

Edit Step 11 Optical Drive Cage  ¶ 

  • Start removing the optical drive cage by removing the back cover.

Edit Step 12  ¶ 

Image 1/3:

Edit Step 12  ¶ 

  • Now, remove the IDE and power cables.

Edit Step 13  ¶ 

Image 1/3: Now, pull the cage away from the front until it is free.

Edit Step 13  ¶ 

  • Remove these two Phillips screws:

  • Now, pull the cage away from the front until it is free.

  • Now, lift the cage out.

Edit Step 14  ¶ 

Image 1/2: My MDD has a 3rd Party 22X SuperDrive, for burning DVD's in Leopard (Thank You Generic Drive Support!)

Edit Step 14  ¶ 

  • 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.

  • My MDD has a 3rd Party 22X SuperDrive, for burning DVD's in Leopard (Thank You Generic Drive Support!)

Edit Step 15 System Fans  ¶ 

Image 1/3: Remove these two Phillips screws:

Edit Step 15 System Fans  ¶ 

  • Optical Fan:

  • Remove these two Phillips screws:

  • Now, slide the plate towards the case, and lift it up, and off.

Edit Step 16  ¶ 

Image 1/2: Now, lift the fan straight up and out.

Edit Step 16  ¶ 

  • Once the cover is removed, disconnect the power cable and thread it under the dust shield.

  • Now, lift the fan straight up and out.

Edit Step 17  ¶ 

Image 1/2: Disconnect the optical drive IDE cable from the logic board.

Edit Step 17  ¶ 

  • System Fan:

  • Disconnect the optical drive IDE cable from the logic board.

  • Now, remove the system fan cable.

Edit Step 18  ¶ 

Image 1/3:

Edit Step 18  ¶ 

  • 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.

Edit Step 19 Power Supply  ¶ 

Image 1/2:

Edit Step 19 Power Supply  ¶ 

  • To remove the power supply connector from the motherboard, push at the top of this clip, and pull the connector off.

Edit Step 20  ¶ 

Image 1/3: Now, thread the power cable out of the small hole it comes through.

Edit Step 20  ¶ 

  • Push on these two clips here to release the power cable.

  • Now, thread the power cable out of the small hole it comes through.

Edit Step 21  ¶ 

Image 1/2: There may be a small hex screw here on the back of the case, it must be removed if present:

Edit Step 21  ¶ 

  • Remove this Phillips screw:

  • There may be a small hex screw here on the back of the case, it must be removed if present:

Edit Step 22  ¶ 

Image 1/2:

Edit Step 22  ¶ 

  • Now, slide the power supply towards the front of the case, and pull it out. It is a little heavy, so don't drop it on the logic board.

Edit Step 23  ¶ 

Image 1/2: The power supply connector has a 25V lead to drive apple ADC displays, so though it is possible to modify an ATX power supply, it won't be able to drive ADC displays, just VGA, or DVI, though the computer will work fine (I've actually tried this).

Edit Step 23  ¶ 

  • The power supply has a 24-Pin connector with non-standard voltages, so dropping in a 24-Pin ATX power supply without modification isn't a great idea.

  • The power supply connector has a 25V lead to drive apple ADC displays, so though it is possible to modify an ATX power supply, it won't be able to drive ADC displays, just VGA, or DVI, though the computer will work fine (I've actually tried this).

  • It also has three 12V/5V rails to drive all six drives (four hard drives, two optical Drives) simultaneously. This is the only Macintosh computer other then the Mac Pro to support six drives.

Edit Step 24  ¶ 

Image 1/2:

Edit Step 24  ¶ 

  • This is also the notoriously loud AcBel 400W "Windtunnel" power supply

Conclusion

To reassemble your device, follow these instructions in reverse order.

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3 Comments

Nice overall, but I don't see the point in removing the fans.

jpkjpkjpk - Reply

Agreed, fan removal totally unnecessary.

maccentric - Reply

Thank you. Used the guide to replace the power supply, in my G4 , with one from a dead G4 I had in the garage.

Jim Asherman - Reply