[CA11] Seatalk RL 70 C Pathfinder

I have a RL70C Pathfinder system installed. It has the 'Mother' unit (where the cards are inserted) and a repeater unit in the cockpit.
The Repeater unit got damaged by moisture and I want to replace it. (the inside screen is discoloured)
Can I use another 'Mother' unit in the cockpit without inserting additional chart cards or does it have to be the identical repeater unit?
The system works extremely well!