Problem(s) Encountered:

Dome encoder is not working properly.  Does not respond to TCS enabled

slews.  Azimuth does not update through the computer.  Dome error advances slowly even with the dome sitting in a parked position.  Operated manually for the remainder of the night.

Solutions:

Tests showed that the encoder appeared to be working correctly for CCW dome motions.  Encoder was not updating however for CW motions.  This would obviously lead to large errors very quickly.  Pulled the interface electronics for the dome readout and replaced chipset.  Since there are only 4 chips to pull, I swapped new ones for all instead of testing each chip individually.  I might try testing the failed set at some point, but I was more concerned with solving the problem for now.  After reinstalling the interface electronics, slewed the telescope around manually to ensure that the encoder was reading out for motions in both directions.  Then slaved the dome to telescope motions and verified that the dome tracks properly.  Finally, homed the dome via the TCS successfully.  Dome systems appear to be back to fully functional.