Need help debugging some iBooks

[punger]

Hello, a while back I won a couple auctions on Ebay. For around £20 total I managed to get three iBook G3s, one iBook G4 and a broken charger (auction was for spares/repairs) . Because of the broken charger I haven't got around to testing them until just this morning when one arrived.

None of these machines seem to get any sort of display so I'll be as detailed as possible:

iBook G3 800MHZ/256MB/30GB/COMBO, Airport card seems to be installed
Startup jingle, CapsLock and NumLock keys display a light when pressed, fans spin

iBook G4 1.33GHZ/256/60G/SuDr/APX
Startup jingle, CapsLock and NumLock keys display a light when pressed, fans spin

iBook G3 700MHZ/256MB/30GB/COMBO
Startup jingle, CapsLock key displays a light when pressed, NumLock doesn't seem to work, can't hear fans spinning but definitely still on

iBook G3 900MHZ/256MB/40GB/COMBO, Airport card seems to be installed
Startup jingle, CapsLock and NumLock keys display a light when pressed, fans spin

Asking here because I only have a PowerMac G5 which works, never tried iBooks before.

Any tips/tricks that might help/further information? Any immediate ideas or causes?

If all of them just have faulty displays then I'm probably bummed

EDIT: Should note all machines are 14"

 

[Dronecatcher]

I would say it's almost 100% likely the screens are bad - hence them being sold as a bundle.

However, my iBook very occasionally boots to a black screen and one of these two resets it:

Reset the PRAM by holding down the Command(Apple), Option(Alt), P and R keys after switching on, wait for three chimes before letting go.

Remove battery (and power cable if attached) and hold the power key down for ten seconds.

 

[Slix]

This is going to sound silly, but I've had this happen with a few different iBooks and PowerBooks, so it's worth a try.

Once it makes the startup chime, try pressing the brightness up button a few times. Somehow sometimes a few of my iBooks and PowerBooks get dimmed all the way down after restarting, and need to have the brightness turned on manually.

PRAM reset is also a good idea, but I wanted to mention my experiences with this to give another idea.