The 26-1 connector is fine, that's the right type for a 25; if your halfmoon says "Chorale - Tremolo" on it, it'll just call up Off and Tremolo on the 25 ('cause it's a single-speed Leslie). Unfortunately the only guess I have for the low volume is that you've got faulty components in the amp. Maybe that's why it was free? (needs an amp rebuild?) The "Orpheus" being single-speed will go back what, about 50 years minimum, so no surprise if you've got some bad caps etc. in there. Others can help more with the specifics. Good luck with it and congrats - it's still awesome if it was FREE!