Canon CP660 Service Manual page 129

1. Secondary Pre-Transfer Charging Bias Generation Circuit
This circuit consists of three signals (Figure 4-6y08) from the DC controller PCB, and
generates the secondary pre-transfer charging DC bias and the secondary pre-transfer
AC bias for application to the secondary pre-transfer charging assembly.
The application voltage to the secondary pre-transfer charging assembly is turned on
and off by the secondary pre-transfer DC bias drive signal and the secondary pre-trans-
fer charging AC bias drive signal. The secondary pre-transfer charging bias signal is used
to switch the level of the secondary pre-transfer charging DC bias according to environ-
mental conditions.
DC control PCB
2. Secondary Transfer Bias Generation Circuit
This circuit is controlled by four signals (Figure 4-609) from the DC controller PCB,
and generates the secondary transfer DC (positive) bias and the secondary transfer DC
(negative) bias for application to the secondary transfer belt.
The secondary transfer DC (positive) bias drive signal is used to turn on and off the
DC (positive) bias applied to the secondary transfer belt, while the secondary DC (nega-
tive) bias drive signal is used to turn on and off the DC (negative) bias applied to the sec-
ondary transfer belt.
The secondary transfer bias level (constant current) control signal and the secondary
transfer bias level (constant voltage) control signals are bias level switch signals, and are
used to switch the secondary transfer DC (positive) bias according to the type of paper
and the conditions of the environment.
DC controller
PCB
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Secondary pre-transfer DC bias
drive signal
Secondary pre-transfer AC bias
drive signal
Secondary pre-transfer
charging bias level switch
signal
Figure 4-608
Secondary transfer DC (positive)
bias drive signal
Secondary transfer DC (negative)
bias drive signal
Secondary transfer bias level (constant current) control signal
Secondary transfer bias (constant voltage) control signal
Figure 4-609
CANON 660/2100 REV.0 FEB. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
CHAPTER 4 IMAGE FORMATION SYSTEM
Secondary pre-transfer
charging assembly
Secondary pre-
transfer charging
AC
bias generation
+
circuit
DC (negative)
Secondary transfer belt
Secondary
transfer bias
generation circuit
DC (positive)
or
DC (negative)
4-31