I am having some issues with my Raymarine RL70C not functioning properly this spring. I spoke with a tech, who suggested that I disconnect the radar input from the back, to see if it is the radome unit (common) or a problem with the dash mounted unit. How do I access the back of the dash? there is a mirror in the bathroom. I am assuming if I remove that, it will have an access panel similar to the one outside of the anchor locker?