OKIDATA DOC-IT3000, Service Manual

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Service Guide DOC-IT3000/4000
Chapter 2 Principles of Operation
Charging
Charging is effected by making a corona discharge to the image drum from the charge wire.
The application of a high voltage (-6Kvdc) from the power supply to the charge wire generates
negative ions in the vicinity of the charge wire through a corona discharge, which are discharged
to the grid plate and the image drum surface. Positive charges are induced in the aluminum base
of the image drum, allowing the negative charges on the image drum surface to be retained.
The aluminum base of the image drum and the grid plate are connected to the ground and a
varistor, respectively, so a rise in the grid plate potential above about -700vdc will lead the
negative charges on the grid plate to the ground via the varistor. During charging, the grid plate is
kept at a potential of about -700vdc, controlling the quantity of negative ions discharged to the
image drum surface and preventing uneven discharging on the image drum surface. Charging
allows the image drum surface to be kept at about -700vdc.
Ozone is generated by a corona discharge around the charge wire. If the ozone is attracted to the
image drum surface, its charged condition would be altered, preventing image stability. To prevent
this, a fan motor removes ozone around the charge wire.
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