Trackball Cleaning

I have cleaned many mice in my time but I never had to clean an optical trackball before. Today I just couldn't take it anymore so I pulled out my toolkit and removed the four little screws, being careful not to drop them, cleaned it out and put it back together.

It looked pretty neat once open with the two little red lights shining out.

Only problem was, while the ball worked fine the clickers no longer worked.

Once again I opened it, being careful not to lose the four little screws and after a while I figured out what I had done wrong.
Once again I put it back together and now I am a happy camper again.

I just wonder why it is I always seem to have to do things twice before I get it right.
(SIGH)