Canon NP6085 Service Manual page 131

c. Developing Bias Control Circuit
The circuit used to control the developing bias
has the following functions:
(1) Turns ON and OFF the AC bias.
(2) Turns ON and OFF the DC bias.
q Turning OFF the AC Bias
ACBTP is '1'.
ACBTP
The AC bias switch circuit turns OFF.
The high-voltage AC transformer
output is cut off.
The above condition cuts off the AC bias to
the developing cylinder.
w Turning ON the AC Bias
is '0'.
ACBTP
The AC bias switching circuit turns ON.
The above condition turns ON the drive cir-
cuit, causing the high-voltage AC trans-
former to supply an AC bias of 1500 Vp-p to
the developing cylinder.
e Controlling the DC Bias Voltage Level
The voltage of the DC bias is determined
by signals (DCBC) from the DC controller
PCB.
When the output of the DC controller PCB
(DECB) increases, the voltage of the DC
bias will also increase.
DC controller PCB
Q158 (master)
Microprocessor
D/A converter
COPYRIGHT © 1996 CANON INC.
Drive circuit
J722
J127
-3
-B3
ACBTP
Switching circuit
J127
-B5
J722
-5
ROED
Switching circuit
J722
J127
-4
-B4
DCBC
Differential amplifier circuit
Figure 3-329
CANON NP6085 REV.0 JULY 1996 PRINTED IN JAPAN (IMPRIME AU JAPON)
d. Roller Electrode Bias Control Circuit
The circuit used to control the roller electrode
bias has the following functions:
(1) Turning ON and OFF the Roller Electrode
q Turning OFF the Roller Electrode
The roller electrode drive signal
'1', i.e., the registration roller is at rest.
The switching circuit turns OFF.
The drive circuit turns OFF.
turns OFF.
The above condition cuts the bias to the
roller electrode.
w Turning ON the Roller Electrode Bias
is '0', i.e., the registration roller is
ROED
rotating.
The switching circuit turns ON.
The drive circuit turns ON.
turns ON.
The above condition supplies a bias of
about -1000 V (effective value) to the roller
electrode.
4. Pre-Cleaning Exposure Assembly
The pre-cleaning exposure assembly houses
63 LEDs from the drum front to the drum rear
used to remove charges remaining on the drum
after transfer/separation, thereby ensuring uni-
form cleaning.
The sequence of operation is the same as
when the pre-exposure LED turns on. (See p.3-23.)
High-voltage transformer 2(HVT2)
High-voltage AC
transformer(T1)
high-voltage DC
transformer(T2)
Drive circuit
Voltage
detection circuit
3. OPERATIONS AND TIMING
The high-voltage DC transformer
The high-voltage DC transformer
Drum
is
ROED
Developing
cylinder
Roller
electrode
3-73