"PowerBook G4 won't boot, no chime"에 답변It seems you’ve tried everything except resetting the SMC (System Management Controller). Here’s a link to Apple’s article on this topic. https://support.apple.com/en-us/HT201295 Good luck!
"Wont BOOT, fans at full throttle"에 답변I realize that this is a very late response, but perhaps it will help others who search the "Answers Index" area here. Have you tried a(n) SMC reset? This can "cure" a lot of issues. (1) Reset SMC of an iMac, Mac Pro, Mac Mini: (2) Shut down the computer. (3) Unplug the computer's power cord. (4) Wait fifteen - twenty seconds. (5) Attach the computer's power cord. (6) Wait five seconds, then press the power button to turn on the computer. OR (1) Shut down your Mac (2) Disconnect the power cord (3) Wait fifteen - twenty seconds. (4) Press and hold the Mac’s power button for 5 seconds (5) Release the button (6) Reattach the power cables and boot the Mac as usual