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10 May 1996
3. DRUM UNIT
3.1 DRUM CHARGE
This copier uses a single corona wire scorotron system to charge the drum.
The corona wire applies a negative charge to the drum surface. The striped
stainless steel grid plate makes the corona charge uniform and controls the
negative charge on the drum surface to -650 V (standard) by applying a
negative grid bias voltage.
The high voltage supply board –C/G gives a constant corona current (–450
µA) to the corona wire, and controls the grid voltage (based on the results of
process control) to maintain proper image density. Grid voltage is controlled
to match changing factors such as a dirty grid plate, dirty charge corona
casing, and OPC chargeability.
The use of the single wire scorotron system has the following advantages.
•
The amount of corrosive gas (O
total current.
•
The life time of the drum is increased due to the decrease in the amount
of corosive gas.
•
Uneven charge problems are alleviated due to the increase of the amount
of current per meter of the corona wire.
, NO
) is reduced due to the decrease in
3
X
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DRUM UNIT
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