Hey- I thought I should pass this on, just did it with my 21" and now the screen looks great and it was really simple to do. If you have a trinitron monitor that has gotten really bright over time, this is a solution. I would add that if you follow the directions here but want a bit cleaner finish, if you pull out the old resistor and replace it with your new one, it is definitly easiest to solder it if you pull the legs thru from the bottom and bend them over to re-solder, instead of placing the resistor on top - check the link and you'll understand what i mean.

Trinitron screen brightness fix
15" MBP late 2008