I have a Pentair Mastertemp 300. The digital display backlight lights up, but does not display any numbers or error codes. I have replaced the memory pad, thermistor, and high limit switch. The heater runs and can be controlled by the memory pad for off and on, and it shows the small lights on the bottom of the pad. Before I purchase a new control board, I want to make sure that there are no other causes for the non display of temperature and ability to see up and down settings. My current memory pad and control board have 6 pins. I am aware that this model control board has been discontinued and replaced by Pentair with an updated model with 8 pins and a matching memory pad that has 8 pins. Now I am totally confused what to do. Can you help me troubleshot? I am a retired builder and am pretty handy fixing things.