I am having problems with my futaba 14sg and my new teleconverter. I try to register to my T14sg with the back conection port and the correct menu but always say "comunitation error". I connect like you say: the 4.8v battery into the side of powerbox legend and the other side to futaba t14sg with the correct polarization. I can not register it.
I have the same problem trying to update with the usb interface adapter, with the correct connection: USB to powerbox legend and batery to sbus2 leyend like says the manual. My computer says that no powerbox device is connected.
I update my powerbox competition srs some days ago to v21 without problems.
What can I do? Please, I need a solution as soon as possible. I think that my powerbox teleconverter is wrong.