Turn the keyboard locking screw located in the middle of the keyboard so that it is parallel to the space bar. A half turn from parallel to parallel will unlock it. Another half turn will lock it again.
Pull the keyboard release tabs toward you and lift up on the keyboard until it pops free.
Remove the seven T8 Torx screws from the lower case.
Using your thumbs, slide the lower case toward the front of the computer.
The lower case may stick in the front on a tab just above the center of the optical drive. Be careful as you work the case off, or you may break the thin strip of plastic just above the drive.
Disconnect the pink and white inverter cable from the inverter board.
The display inverter has orange plastic shielding around it that looks similar to the tape used elsewhere within the computer. Do not remove the shielding from the inverter.
Lift the DC-In board out of the computer by pulling up and away from you.
If you don't have a 667 MHz computer, there is a fan in this location which makes it a bit difficult to remove the DC-In board.
If there is a fan present, rotate the DC-In board slightly clockwise before easing it out at a slight angle in order to clear the fan clamp on top of it.
Before continuing, place a soft cloth on your work surface to rest the computer on. Turn the G4 over and place it on the cloth.
Disconnect the four indicated connectors from the logic board.
The large multicolor cable may be difficult to free.
The top center cable may not need to be disconnected to remove the modem filter board. It connects to the logic board fan to its immediate left, which is attached to the logic board itself.
Disconnect the two connectors from the modem filter board.
To the immediate right of the modem filter board, the heatsink has two sets of five fins with a double-wide space in between them. This space is where the gray & black coiled wire is supposed to go to ensure a flush fit.
Remove the modem filter board from the computer by pulling up and to the right.
There is a small plastic post which helps hold the modem filter board in place. You need to clear this post to remove the modem filter board from the computer.
Remove the seven T8 Torx screws from the logic board.
The five black screws go on the right side of the logic board, the large silver screw goes at the top, and the small silver screw is located on the left side.
Disconnect the 5 indicated connectors from the logic board, removing tape as necessary.
Reassembly Tip: Reseating the logic board will be much easier if you use kapton tape to hold these five connectors out of the way until it is in place.
Caution: If taping the connectors back, be careful not to use tape with anything but very weak adhesive (i.e. kapton tape). Even electrical tape can pull the paint off the hinges when removed.
Carefully lift the logic board up and pull it away from you.
This step requires some force, but if the logic board will not come up, make sure that you have removed all the necessary screws and connectors. Warming the heatsink with a heatgun or blow dryer will help release the logic board.
On 800 MHz and above G4s, you must disconnect the fan cable from the logic board before you lift the board entirely off.