The autocenter script wasn't working in a very robust way (sometimes the socket connection to the controller failed, some times no motion was obtained after issuing a command). So I rewrote the interface to the Newport controller using the http server interface. The code is in picomotor8742_http.py. This version seems much more robust.

There is a large wandering line that spans all frequencies. Not sure what the origin is, but it will need some noise hunting. Here are spectrograms of all four QPD X signals. The line is visible in all of them, at the same frequency. So it's definitely something external coupling into the light or the QPD electronics. It's not visible in the sum of the QPD quadrants, but maybe just because it's buried in noise.

Finally, I tried to excite the disks, but I couldn't get any motion of the optical lever beams. To be investigated, there might simply be some cables disconnected.