Whenever an electronic device displays a blank screen it means trouble, a water softener is no different.  What could cause this issue?  Often a power surge or brown out can cause damage resulting in this condition.

The first step in problem solving this dilemma is checking to make sure that the water softener is plugged into a working, non switched, electrical outlet.  Once that has been confirmed the next step is to remove the face plate and confirm that all the connections at the bottom of the circuit board are connected.

There are only two components that could be causing this problem, the transformer or the circuit board.  You will need a basic voltage meter like this one to narrow down the defective part.  Un plug the electrical connection from the bottom of the circuit board and test to see if there is any voltage coming through the transformer, if so, the circuit board needs to be replaced, (Clack Circuit Boards) if not replace the transformer first. Clack Transformer

How can you minimize the chances of this happening again?  Purchase a surge suppressor power bar, like what you use for a television or computer and plug your water softener and all other water treatment components into it.