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Introduction

The Power Mac G4 MDD uses a uniquely shaped 344W or 400W AcBel or Samsung power supply. It has a 24-pin connector (not 24-pin ATX!). The original AcBel power supplies were notoriously loud, earning the Power Mac G4 MDD the nickname "WindTunnel".

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  1. 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.
    • 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:

  2. Unplug the computer. Unplug the power supply and all external connections from the computer. Pull on the side lever and lower the side of the case.
    • Unplug the computer.

    • Unplug the power supply and all external connections from the computer.

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

  3. The hard drive cages are located here.
    • The hard drive cages are located here.

  4. Cage 1 Start by removing this screw. Remove the ATA-66/ IDE ribbon cable from the motherboard.
    • Cage 1

    • Start by removing this screw.

    • Remove the ATA-66/ IDE ribbon cable from the motherboard.

  5. Now, remove the power connection from the drives. Now, remove the power connection from the drives.
    • Now, remove the power connection from the drives.

  6. Push this tab down, and pull the cage toward you. Now, you can set cage 1 aside. Now, you can set cage 1 aside.
    • Push this tab down, and pull the cage toward you.

    • Now, you can set cage 1 aside.

  7. Cage 2: Remove this Phillips screw:
    • Cage 2:

    • Remove this Phillips screw:

    • Disconnect this IDE ribbon cable from the logic board.

  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.
    • 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.

  9. With the ribbon cable clip free, pull this tab towards you, slide the cage up until it hits the platform under the power supply, and pull it away. Now, set the cage on top of the CPU, and remove the power connectors. Now, set the cage on top of the CPU, and remove the power connectors.
    • With the ribbon cable clip free, pull this tab towards you, slide the cage up until it hits the platform under the power supply, and pull it away.

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

  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, then slide the drives out.
    • 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, then slide the drives out.

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

    • The MDD does not have a 128GB drive limit like older Macs. My MDD has 3 drives (a 400GB Hitatchi Deskstar, 40GB Seagate Barracuda 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.

    Thanks - excellent tutorial!

    Question: If you have a single internal drive, and a connected extrenal drive via firewire or usb, what jumper setting should be set for the internal drive and the external drive? Booting into Mac OS 9 natively (not via Classic) on the internal drive seems to be sensitive to the jumper settings and I’m having issues getting it to work.

    LTG Seb - Réponse

    LTG: The jumper settings on the internal drives make no difference for any external drives. The jumper settings are to distinguish between Master and Slave drives when there are two drives connected to one ATA/IDE ribbon cable. Since the ATA/IDE drive ribbon cables are purely internal to the Mac, they have no connection to any external drives.

    johnsawyercjs -

    I ran my MDD with 3-750GB IDE HD’s. When they got flakey I replaced them with 2TB SATA drives in the back cage with a cheap SATA to PATA adapter and they formatted out to 1.8TB. I then cloned (CCC) the boot drive to one of the 1.8TB drives. It boots to the new drive and every thing seems to operate like normal. I don’t know how big we can go but we know that a MDD will handle at least 2TB HD’s and I have 5TB in my iMac 15,1

    Glenn Stettler - Réponse

    Glenn: you might get some extra speed from those SATA drives if you install a SATA card into one of the PCI slots (if you can still find one), and connect the drives to it. I ran a couple SATA drives in my MDD this way for years, before the MDD’s power supply burned out.

    johnsawyercjs -

    This is an amazing blog. This is my computer, I think a 2004 model. I have a question though; I bought a 1 TB 3.5’ SATA WD Black Performance Hard Drive and have 2 weeks to return it. It appears I need a bridge adapter from the old IDE ATA to the newer SATA, will this adapter work? :

    https://www.amazon.com/QNINE-Adapter-Dri...

    My dilemma: My hard drive is clicking like crazy (freezing) and I use this machine paired to my old Digidesign DigiRack 001 recording system. It’s proprietary and not forward compatible to anything other than OS 10.3.2 and I need to desperately clone this old Toshiba 80g hard drive in order to keep functioning on this version of Protools.

    Carlos Branham, Jr. - Réponse

    Correction: My G4 must not be the MMD version. Doesn’t have all those peripherals in the rear. Wish I could add a photo. I’m thinking it was build in 2003.

    Carlos Branham, Jr. -

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

  12. Now, remove the IDE and power cables from the drives. Now, remove the IDE and power cables from the drives. Now, remove the IDE and power cables from the drives.
    • Now, remove the IDE and power cables from the drives.

  13. Remove these two Phillips screws: Pull the cage away from the front until it is free. Slide the cage towards you, and out of the Mac.
    • Remove these two Phillips screws:

    • Pull the cage away from the front until it is free.

    • Slide the cage towards you, and out of the Mac.

  14. To remove the drive(s) from the cage, remove the two screws on each side of the drive(s), then 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!)
    • To remove the drive(s) from the cage, remove the two screws on each side of the drive(s), then 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!)

  15. You may find removing the system fan is unnecessary to remove the power supply cable from behind it, but if you're unfamiliar with how the power supply cable is situated behind the fan, this step is useful in seeing this. Disconnect the optical drive IDE/ATA-33 cable from the logic board.
    • You may find removing the system fan is unnecessary to remove the power supply cable from behind it, but if you're unfamiliar with how the power supply cable is situated behind the fan, this step is useful in seeing this.

    • Disconnect the optical drive IDE/ATA-33 cable from the logic board.

    • Disconnect the system fan 2-wire power cable connector from the logic board.

  16. Grab the system fan by its sides and pull it up and out. The system fan is very large and loud, compared to standard sized fans. Grab the system fan by its sides and pull it up and out. The system fan is very large and loud, compared to standard sized fans. Grab the system fan by its sides and pull it up and out. The system fan is very large and loud, compared to standard sized fans.
    • Grab the system fan by its sides and pull it up and out. The system fan is very large and loud, compared to standard sized fans.

  17. To remove the power supply connector from the motherboard, push the top end of this clip towards the power supply connector, and pull the connector up and off the motherboard. If the connector seems to be stuck, rock it back and forth a tiny bit to loosen up the connection, then pull up again. To remove the power supply connector from the motherboard, push the top end of this clip towards the power supply connector, and pull the connector up and off the motherboard. If the connector seems to be stuck, rock it back and forth a tiny bit to loosen up the connection, then pull up again.
    • To remove the power supply connector from the motherboard, push the top end of this clip towards the power supply connector, and pull the connector up and off the motherboard. If the connector seems to be stuck, rock it back and forth a tiny bit to loosen up the connection, then pull up again.

  18. Push on these two clips here to release the power cable. Thread the power cable out of the small hole it comes through, at the far side of the Mac. Thread the power cable out of the small hole it comes through, at the far side of the Mac.
    • Push on these two clips here to release the power cable.

    • Thread the power cable out of the small hole it comes through, at the far side of the Mac.

  19. Remove this Phillips screw: There may be a small 2.5mm hex (not Torx) screw here on the back of the case, it must be removed if present:
    • Remove this Phillips screw:

    • There may be a small 2.5mm hex (not Torx) screw here on the back of the case, it must be removed if present:

  20. 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. Disconnect any drive power connectors that you may not have already connected. 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. Disconnect any drive power connectors that you may not have already connected.
    • 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. Disconnect any drive power connectors that you may not have already connected.

  21. 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).
    • 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 than the Mac Pro to support six drives.

  22. This is also the notoriously loud AcBel 400W "Windtunnel" power supply This is also the notoriously loud AcBel 400W "Windtunnel" power supply
    • 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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Chris Green

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

jpkjpkjpk - Réponse

Agreed, fan removal totally unnecessary.

maccentric - Réponse

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 - Réponse

Great guide ... I didn't remove either of the fans and was able to remove Power Supply Unit. Now trying to decide how to get it fixed or to get a rebuilt or ....

Earth Bound Traveler - Réponse

Nice instructions and photos. Another set I'd found on line specified a T-10 Torx for case screw connecting the power supply -- wrong, for mine anyway -- 2 mm hex worked for me.

DaR - Réponse

DaR: this is usually a 2.5mm hex screw

johnsawyercjs -

If you have a no-power issue, I have successfully repaired the power supply by changing the capacitor near the 5VSB circuit. In my case it was slightly bulged, once removed it was completely non-functional. It is a 10V 1000uF capacitor, I replaced it with a 1000uF 16V capacitor I had unhand. Follow the 5VSB wire (purple wire) to the PCB and check the capacitors near by. Fully functional now.

Scott Gibson - Réponse

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