I don't think you've run the Apple Hardware Test on your PowerBook, because you haven't got any discs, but with the help of this Apple doc "you can download the appropriate CD image listed below and burn an AHT CD." (Credit to knoodles for the link.)

After you burn your CD, boot your PB from it, run the "Extended Test" in loop-mode (control-L) for *at least* 5 loops, and see what, if anything, it tells you.

Keep us posted

The new Great Equalizer is the SEND button.

In Memory of Harv: Those who can make you believe absurdities can make you commit atrocities. ~Voltaire