The other side of the pin is occupied by the pot that is on the last pic. I was thinking of jumpering a wire from that middle pin it where it teminates (which is on the tube socket) however am not particularly sure of its effect as the pot is used to adjust the voltages heading/coming from it. The setup is from a uncompleted tube preamp project that I was thinking of restarting again. Anyone know of a place where i can send it to for final touch up? Still thinking of working out the cabinet design and fabricating it.