birdinlay, besides the answer from @mayer try following the Apple troubleshooting steps:
The computer will not power on (no fan movement, hard drive spin up and display is not lit)
1. Remove any connected peripherals and eject any PC card.
2. Check that the battery has enough charge to start the computer by pressing the button next to the LEDs on the battery. At least one LED must light solid (not flashing).
3. Connect a known-good Apple 65W Portable Power Adapter and power cord or plug to a known-good power outlet; make sure the DC plug is firmly inserted. The DC plug should light up, if not, replace DC-in board.
Important: The Apple 65W Portable Power Adapter is highly recommended to be used with the PowerBook G4 17-inch series computers. The adapters can be identified by 65W in the name and markings, and the metal securing-stud on the plug connector. Although previous 45W power adapters (see Knowledge Base article 88231 PowerBook and iBook: Apple Power Adapter) are plug compatible with the
PowerBook G4 17-inch series, it may not provide sufficient power during some activities and power may be drawn temporarily from the battery.
4. Try powering up without the battery installed (only works with 65W power adapter).
5. Reset the power manager. See procedures under the “Resetting the Power Manager Unit (PMU)” heading in the Hardware Troubleshooting Tools and Tips section. Warning: Resetting the power manager will permanently remove a RAM disk, if present, and all of its contents. You will also need to reset the date and time (using the Date & Time system preference pane).
6. For PowerBook G4 (17-inch Double-Layer SD) only, boot up the system and check the sleep indicator. If it turns on solid and turns off, the main logic board is getting power and completing the boot cycle. If no video appears, there is an issue turning the video on or system software is corrupted. Try booting off the DVD. If the light does not turn off, the boot cycle is not being complete. This may be cause by the hard drive not being seen by the system, system software corrupted or possibly a hardware issue.
7. Press Caps Lock key to see if key light comes on. If it does, hold power button down for six seconds to shut down the computer and restart.
8. If it still doesn’t start, verify power button cable is connected properly to top case flex cable assembly and that the flex cable is connected correctly to the logic board, if power button is not functioning correctly or damaged, replace the top case.
9. Disconnect keyboard completely. Inspect connectors. Restart with keyboard disconnected.
10. Remove any additional RAM.
Hardware Symptom Charts PowerBook G4 (17-inch DLSD/1.67/1.5/1.33GHz) Troubleshooting - 19
11. Try disconnecting the AirPort Extreme flex connector from the logic board and start the computer. If it starts, shut it down and check the flex cable connector and the connector on the logic board and replace the damaged parts.
12. Reseat these flex cables:
• DC-in flex cable
• Hard drive flex cable (will boot to flashing folder)
• Optical drive flex cable
• PC card cage flex cable
• Keyboard flex cable (on PowerBook G4 (17-inch 1.67GHz) only)
• Trackpad flex cable
• Right USB flex cable
• Modem flex cable
If the computer starts up, inspect the flex cable connector and its connector on the logic board for damage and replace the damaged parts.
13. Remove AirPort Extreme Card.
14. Try known-good DC-in board.
15. Replace logic board.
Let us know what you find out.