Won't Turn On

Within the past 6-7 years, I have been through 2 powerbook G4's The first one was a 15" Powerbook Titanium DVI, one morning it wouldn't start, and I decided to take it to a computer repair place, since i don't live near an apple store, and they couldn't fix it, but said that they could try a new logic board, for a few hundred bucks, so i decided to just replace it with a 17" 1.67Ghz Low-Rez PB G4 Aluminum. The First powerbook wouldn't start at all, the CD drive would appear to spin up, and than the Computer would heat up near the cpu, like it would as if it was on, but that was about it, also, caps lock would work on the keyboard (the light would turn on) and for some strange reason, F5 would turn on the num lock light instead of the num lock key. The second powerbook worked for about 2 years, but one day, i dropped it, and it worked, i picked it up, and continued to use it, and later shut it off, to charge it. Upon turning it back on, it wouldn't work, no boot, no chime, no video, it was completly dead just like the other one, the drive would spin, and it would get warm, but nothing else, and just like the other one, the caps lock worked, and the F5 key would turn on num lock, just like the other one, i took it to the computer repair place, just like the last one, and they checked for basic fults, dislodged cables, ram, ect, but found nothing, and offered to replace the logic board again, but i decided to just let it sit in a corner, and wait for the price of PowerBook G4 parts to go down, so i might replace it, unfortionatly it's still 800$ for a new baord, and doesn't really seem worth it, but i was wondering if there ware any commonly known issues with these computer's that would cause symptoms like these, and if i might be able to fix somthing, and save the computer.

Thanks,

Chris