After I replaced the hard drive in my old iBook G3 (with the help of iFixit guides), it will not boot connected to mains power, only with the battery. It also always returns its date/time settings to its "zero-hour", when it left the production line.
The G4 suffered a fall and no longer "finds" the HD to start. In addition it has a yellow vertical line on the monitor at the beginning of its rightmost third part to the left.
I suspect a logical board problem on the G3, and some physical damage on the G4's HDD.