A rotatable charging apparatus includes a length extending between a first
end and a second end, with the rotatable charging apparatus centered about
an axis parallel to the length. The rotatable charging apparatus outer
periphery forms N apparatus positions. One charging device is fixed to
each of N-1 apparatus positions. The remaining (Nth) apparatus position is
devoid of a charging device, thus forming an "empty" charging device
position. A host printing machine selectively causes the rotatable
charging apparatus to rotate about its axis thereby selectively position
any of its N-1 charging devices to face a proximately-located
photosensitive element. When a problem exists with the current charging
device, or when the total number of operating hours of the current
charging device exceeds a fixed threshold, the printing machine causes the
rotatable charging apparatus to rotate from its current charging device to
position a new charging device facing the photosensitive element. Also,
the printing machine causes the rotatable charging apparatus to rotate
from its current charging device to the empty charging device position
facing the photosensitive element when a power-down or hard-stop condition
exists in the printing machine.