This is a very old post but I thought I would answer it for future viewers. I just replaced the bulb in my x20 and it was delicate work but it functions once again as new. The bulb is located inside a brass enclosure at the top of the screen. Do not separate the layers of the screen. Simply remove enough screws to loosen the frame and work it off the top without putting pressure on the screen itself. There are 4 brass screws that are very small that hold the brass light enclosure on, so remove them. Carefully work the enclosure off, it will tear away from a screen layer it is glued to but no worries, it will slide back in by tapping it down carefully in place after you have freed up the light enclosure completely. Replace the bulb and reverse the process but don't worry about gluing it back, it will stay in place and function well just by replacing the screws. I used a 12.1" bulb from another model of IBM and it worked fine. The delicate part is carefully removing the bulb from the brass backbone and put it into the backbone from your unit. You have a relatively easy job ahead if you have a bulb and brass enclosure from the same screen! Cheers. GW