This article explains how to replace the bottom housing in a PowerBook G4 computer. You may also view the following procedure in QuickTime at http://www.info.apple.com/installparts .

Be sure to follow the instructions in this sheet carefully. Failure to follow these instructions could result in damage to your equipment and may void your warranty.

Warning : Sharp edges can exist inside your computer and on any parts being removed or installed. Use caution to avoid injury.

Replacing the modem requires these basic steps:

• Turn off the computer.
• Remove any cables and the battery.
• Remove the bottom case from the computer.
• Attach the new bottom case to the computer.
• Reinstall the battery and reconnect any cables.

Note : Written and video instructions covering customer-installable parts are available at:
http://www.info.apple.com/installparts/ .

Removing the Bottom Case

1. Place your computer on a clean, flat surface.

2. Shut down your computer. Disconnect the power cord and any other cables connected to the computer.
Warning : Always turn off your computer before opening its case to avoid damaging its internal components.
Warning : The internal components of your PowerBook may be hot. If you have been using your PowerBook, wait 30 minutes after shutting it down to let the internal components cool before continuing.

3. Place a towel or soft cloth on a table in front of you. The towel or cloth will protect the keyboard and display area of the PowerBook when you flip it over to remove the bottom case. Make sure it covers an area large enough for your PowerBook and that it hangs over the edge of the table.

4. With the display open at an angle greater than 90 degrees, carefully flip the PowerBook over and lay it flat, fully on the table. Make sure the display hangs over the edge of the table and rests lightly on your lap.

5. Slide the battery compartment latch to remove the battery. Make sure to return the battery latch fully to the right. Removing the battery will help you remove the bottom case and prevent you from accidentally turning on the computer while installing the AirPort Card.

6. Using a Phillips screwdriver, remove the eight screws that secure the bottom case to the PowerBook (in the order shown in the illustration below).
Important : To avoid damaging the case, be careful that the screwdriver tip does not slip out of the screw head during removal.

7. To remove the bottom case you will need to disengage it at the left and right sides, then carefully pivot it forward to release a retaining clip near the DVD drive slot, as follows.
Important : Do not push on the rubber feet of the bottom case.

At the left side, carefully slide the bottom case slightly up and away from you by pushing on it just above the hinge of the display, and at the same time from within the battery compartment, pushing away from you on the edge of the bottom case, until the left side releases.

8. At the right side, again carefully slide the bottom case slightly up and away from you by pushing it just above the hinge of the display, and at the same time from within the battery compartment, pushing away from you at the right-most edge of the bottom case, until the right side releases.

9. When both the left and right sides have released, carefully pull up on the bottom case at the edge that is closest to you and rotate it away from you, pivoting evenly over the front edge to release a retaining clip that is located near the DVD drive slot.
Important: Do not force, twist or pry the bottom case if it binds or resists. The case should remove easily. If not, follow step 7 again, until the case releases.

Installing the Bottom Case

1. To attach the bottom case, align the notches on the right and left sides of the case (some of these can be viewed through the battery opening). Then press down and toward you slightly to secure the case.

Verify that the case lies flat and fits properly around the battery latch and that the alignment tab that protrudes on the underside of the bottom case, shown in the illustration below, has seated properly.

The case edges should line up smoothly.

Note : Applying pressure to the bottom case at the back of the battery compartment opening, near the latch, and on the front and back outside edges of the case can help with alignment.

2. Check that the eight screw holes on the case align with the holes on the computer. Verify that the display rests on your lap as shown in the first figure.

3. Replace the eight screws (in the order shown in the illustration below). Do not overtighten or damage could result. Note : The screws must go in straight and easily; if not, readjust the bottom case for proper alignment.

Important : To avoid damaging the case, be careful that the screwdriver tip does not slip out of the screw head during tightening.

4. Replace the battery.

5. Turn the computer over so that the DVD slot faces you. Just below the center of the DVD slot, verify that the bottom case is flush with the front edge of the slot. If the case is slightly bowed and there is a gap, carefully pull the bottom edge of the DVD slot until it clicks into place and becomes flush with the bottom case.

6. Reconnect the power cord and any other cables. Restart your computer.
Warning : Never turn on your computer unless all of its internal, external, and case parts are securely installed. Operating the computer when its case is open or missing parts can damage your computer or cause injury.