Fixing the backlight cutting out when the screen is tilted past about 60 degrees on an iBook 500. The (poor) design of the hinge assembly causes the cables that pass through it to be over-stressed and eventually break. Part no. 922-5017 (inverter cable with reed switch) was replaced (available in the UK from www.applemacparts.com).
Steps to take:
Instructions for most of the above steps are in the iBook service manual.
Below are photos during the fixing that may be of use if you take the plunge and try it yourself.