Question
I have changed the fuse and 3v battery and the controller still shows PR OFF. Is there anything else I can do to check and see if board is still good or whether to buy another controller?

Answer
Hey Scott, The only thing I could suggest, is on the bottom you will see the terminal strip that the wires are hooked to. The 2 far left wires are marked 24 vac, these are the wires from the transformer that supply power to the controller. Check the voltage on these wires with a volt/ohm meter and see if you are getting around 24 volts (23 to 26). If you are not getting the proper voltage, then the transformer is bad and needs to be replaced, and that could be why you are getting the power off (PR off) reading. If the transformer is okay, then the micro-processor is probably defective and it would be better to get a new controller. Good luck and have a great day.