My RD1200 has a blank screen. Checked power & battery, both good.

How do I get to the fuse to check whether that is the problem?

You can look here and see if it helps. It shows a fuse #4.

http://www.irritrol.com/controller_manuals/pdfs/manual_raindial07.pdf

Original source page:

http://www.irritrol.com/controllers/controllers_raindial.html