Problem(s) Encountered:

Attempted to rotate spectrograph 77 degrees, unplugged instrument and after replugging and rebooting were unable to get it to connect with the telescope again.

Solution:

Main power cord for everything on the telescope was pulled out.  Ground prong of connector ripped off.  New connector installed.

Large-scale motions of the rotator should ALWAYS be performed from within the dome.  Perhaps the cable would not have been damaged if it was discovered earlier.