Well for the benefit of other forum readers. If a button does not work you may get as lucky as I was. the F3 button was infact not working...I opened the keyboard to expose the buttons. The buttons comprise of three parts. The knob, the casing and the actual button switch. I removed the knob and the casing to expose the switch and sprayed liquid air in and around the button. VICTORY. It probrably managed to remove dirt or some other obstruction that prevented the button from making contact. Between fixing the black screen problem, changing the faulty floppy drive and repairing a button, I can only wonder what is next...