Backlight refuses to work when screen open more than 45 degrees?

Hi all,

I recently bought an iBook G4, July 2005, 1.33GHz model. The machine works perfectly, except for the fact that the backlight refuses to be on if the screen is at a less than right angle with the body of the machine. In other words, to make the backlight work, I have to open the screen more than 45 degrees, and then it works brilliantly. I have discovered that if it doesn't work, all I have to do is put it to sleep then wake it up again, making sure to open it more than 45 degrees, and then it works. Pushing it less than 45 degrees immediately results in the backlight turning off, but I can still see the dim screen. I know that the backlight isn't broken since it works at certain angles. I have heard about issues with an inverter cable or something, but can't fathom specifically what my issue is. Any help is appreciated. Thank you in advance!