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CHARGE
2.2 CHARGE CORONA CIRCUIT
The DC power supply board supplies +24 volts (Va) to the charge/bias/grid
power pack as the power supply source. About 8 seconds after the copy
process starts, the CPU drops CN107-B14 from +24 volts to 0 volt. This
actuates the dc/dc converter within the power pack which applies a high
negative voltage of approximately –5.3 kV to the charge corona wire. The
corona wire then generates a negative corona charge.
The grid limits the maximum corona charge to –940 volts. This ensures that
the charge does not fluctuate and an even charge is applied to the drum
surface. When developing the test pattern for the image density sensor, the
grid charge is –460 volts.
The copy grid voltage, and ID sensor grid voltage amounts can be adjusted
using service program modes #23 and #22, respectively.
The grid drive signal applied to CN1-6 is a pulse width modulated signal. As
the width of the pulses applied increases, the strength of the grid charge also
increases. The main board monitors the grid charge at CN110-8 and controls
the width of the drive pulses based on this feedback.
Charge/Bias/Grid PP
Charge / Bias Grid PP
DC/DC
Converter
DC/DC
Converter
CN1-1
CN1-2
CN1-3
CN1-6
CN1-10
2-4
31 December 1992
DC Power
CN2
-6
24V Va
GND
CN107
Main Board
-B14
24
Charge
CN110
Grid Drive
-1
0/5
Grid monitor
-8
0
2.5
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