Some iBook G3s have the problem of their screens having lines or staying black when booting. The problem is with the graphics chip. To fix this problem we must reflow the the solder beads in the graphics chip. In this instructable I use a heat gun, but you can also use a blowtorch on low. Below is a picture of a ballgrid array graphics chip like the iBook's.
This is a very risky project so don't do this unless you don't want your iBook any more(except for parts).
Step 1: Finding the Graphics Chip
First you must locate the graphics chip. It is on the back of the logic board with some foam on top. Remove the foam carefully.
Step 2: Applying the Tinfoil
Apply 4 sheets of tinfoil around the chip cut a hole for the chip. Place a little solder on top of the chip.
Step 3: Using the Heat Gun
Use the heat gun on low. Start 12 inches above the chip and hold it there for 10 seconds. Slowly lower the heat gun until it is 3 inches away. When the solder on the chip melts, hold the heat gun for 10 more seconds. Be extremely careful not to bump the chip and keep the board level.
Step 4: Boot the IBook
Put the laptop back together and boot it. If it doesn't book you overcooked the chip. Scrap for parts. If it has the same problem lather, wash and repeat.