I dont think I can -in fact -I know I cannot!
In this day and age where keyboards start from around $20 I do not think I would even bother.
I now buy a keyboard that has a "backlight" -that is -when your fingers get near it, and if the room is dark, it lights up so you can see the keys without lights -I hate lights in the day so this is ideal for me.
This is of course more expensive, however I would not bother trying to fix a keyboard.