  The D0 experiment was designed in the mid 1980s and ran at the Fermilab pp
collider from 1992 through 2011. I describe the uranium-liquid argon
calorimeter and its readout electronic which was upgraded in the late 1990s to
handle the higher luminosity of the upgraded Tevatron during its second running
period from 2001-2011. I summarize maintaining the calorimeter for 20 years of
data taking. I further describe a few issues that arose during that time,
including different types of noise and the anomalous high voltage currents seen
only in the central calorimeter.
