I've just started piddling with the galvos Steve gave me, and after discovering and loosening the shaft lockdown hex screw, there seems so be 3 seperate 'indents' that I can feel as the shaft is rotated (VERY gently, I assure) I've read about breaking the centering spring. I thought there was a center position and that's it. Applying V+ will rotate one way and -V the opposite. I dont know what these 3 different indent positions are for

The galvos do work; plus and minus 10V does move the shaft back and forth.