Recieved my 8 zone gen 2 rachio today. I pulled the cover off my ancient nelson controller and obviously the identification marks on the nelson are not the same as the rachio. I have a 7 zone system. No rain sensors that I am aware of (moved into the home several months ago). All the zones work.
From left to right on the nelson controller…
Two 9V slots (1 thin brown wire and 1 thin red wire)
Two 24V slots (1 thin black wire and 1 thin white wire)
1 C slot (2 white wires twisted together in same slot)
P - empty slot