If the HD is broken you should probably see the question mark icon (so it should power up) Its probably a screen problem.
You Should reset the PMU to see if the power is going well,The Power Manager is an integrated circuit (computer chip) that is usually on the logic board of the PowerBook and iBook. As the name implies, it is responsible for power management of the computer :
Resetting PowerBook and iBook Power Management Unit (PMU) - Soporte técnico de Apple
- Force Quit (Option-Command-Escape)
- Restart (Control-Command-Power)
- Force Shut Down (press the power button for 10 seconds)
Then if that dosent work: Open the clamshell and check if the video cable its connected.
http://www.powerbookmedic.com/xcart1/files/AppleClamshelliBookRep.pdf
(check page 15 of 21)
Let me know what happens!
=)