Developing Bias - Canon NP6320 Service Manual

CHAPTER 4 IMAGE FORMATION SYSTEM
2. Controlling the DC Bias
The differential amplifier of Figure 4-402 operates when DCBC is 16V or below. (The range
of DCBC (analog) is 6 to 16V, as set by the copy density cursor or the AE system.)
Differential amplifier goes ON.
Variable pulse-width oscillator goes ON.
DC high-voltage transformer goes ON.
The DC bias is applied to the developing cylinder.
The copy density knob changes the DC component of the developing bias as shown in Figure
4-401.
Figure 4-401 Changes in Development Bias
DC controller PCB
AE sensor
Copy density
knob
Copy density
lever
D/A
Black
converter
developing
assembly
4-10
COPYRIGHT © 1999 CANON INC.
DCBC
−500V to −0V
DC component of

developing bias

Copy density lever scale
(5)
-100
-200
-300
-400
-500
DC bias
(DC component) by Copy Density Knob
High-voltage transformer unit (HVT)
AC bias
switching
Square
circuit
wave
oscillator
ACBON
Differential
Variable
amplifier
pulse-width
DCBC
oscillator
Q1
Figure 4-402
6V to 16V
T1 drive
circuit
AC high-voltage
24V
transformer T1
24V
T2 drive
circuit
Rectifier
DC high-voltage
transformer T2
CANON NP6320 REV.0 DEC. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
Photo
sensitive
drum
Developing
cylinder
Static charge
eliminator