I finally got my 1721 sticky track ball problem solved.. I opened the radar
case and expected I would have reasonable access. What I found was the
assembly would require major disassembly of the radar display.

I'm still not sure of why it was difficult to turn, but I finally took a
damp soapy rag to the ball, got it wet and rolled it around until it seemed
to turn freely in all directions. I then wiped it dry and gave it a coat of
silcone spray. Rolled the ball around for a couple minutes and everything is
working smoothly.

I suspect it had accumulated some dust and dirt over time.. Future
maintenance will include wiping the track ball with a damp cloth.

Steve
s/v Good Intentions