Canon PC720 Service Manual - Page 64

Controlling, Developing, Separation, Static, Eliminator

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ME OPERATIONS AND TIMING E. Controlling the Developing/ Separation Static Eliminator Bias 1. Outline Figure 3-308 shows the circuit that con- trols the developing/separation static eliminator bias, and the circuit has the following functions: • turns on and off the DC component. • turns on and off the AC component. • controls the voltage level of the DC bias according to type of developing assembly. • controls the voltage level of the DC bias according to the copy density settings. The developing cylinder is given AC and DC biases during copying operation. While the photosensitive drum is rotating, except during development, about -500 V is applied to the developing cylinder regardless of the position of the density adjusting lever, thereby preventing adhesion of excess toner to the surface of the photosensitive drum. AC power supply 1 Transformer T101 Transformer T2O1 1=.4 5V Amplifier 205 -ea rn r9i) Ea Photosensitive Developing drum cylinder Ampl fier/ rect fier - circuit Static eliminator 3 - 24 Microprocessor Oc utt < Composite current PCB o OV 7=C.0D O - RS 25 CI 0 o a> ) O o tu 25 O DC controller PCB Microprocessor o Co oo 0) a) C w 0) :FEO- o O • TcDD.O al at 8 8 Density correction swlch (ST101) AE/intensity senso PCB Senso PCB Control panel Figure 3-308 COPYRIGHT © 1994 CANON INC. CANON PC72074017501710 REIM AUG.1994 PRINTED IN JAPAN omPFumt AU JAPONI

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ME
OPERATIONS
AND
TIMING
E.
Controlling
the
Developing/
Separation
Static
Eliminator
Bias
1.
Outline
Figure
3-308
shows
the
circuit
that
con-
trols
the
developing/separation
static
elimi-
nator
bias,
and
the
circuit
has
the
following
functions:
•
turns
on
and
off
the
DC
component.
•
turns
on
and
off
the
AC
component.
•
controls
the
voltage
level
of
the
DC
bias
according
to
type
of
developing
AC
power
supply
assembly.
•
controls
the
voltage
level
of
the
DC
bias
according
to
the
copy
density
set-
tings.
The
developing
cylinder
is
given
AC
and
DC
biases
during
copying
operation.
While
the
photosensitive
drum
is
rotat-
ing,
except
during
development,
about
-500
V
is
applied
to
the
developing
cylinder
regardless
of
the
position
of
the
density
adjusting
lever,
thereby
preventing
adhesion
of
excess
toner
to
the
surface
of
the
photo-
sensitive
drum.
1
Transformer
T101
9
ri)
1.
4
=
5V
Transformer
T2O1
Amplifier
205
-
ea
rn
Ea
Ampl
fier/
rect
fier
—
circuit
Microprocessor
O
c
utt
o
OV
7.
0
—
=
CD RS
O
25
CI
Composite
current
PCB
<
a)
o
o
>
tu
O
25
0
O
DC
controller
PCB
Microprocessor
Co
w
o
o
0)
o
a)
C
0)
:O
o
F
E
O
-
•
T
D
-
cD
.
O
al
at
8
8
Density
correction
swlch
(ST101)
AE/intensity
senso
PCB
Senso
PCB
Control
panel
Figure
3-308
Photosensitive
drum
Static
eliminator
Developing
cylinder
3
-
24
COPYRIGHT
©
1994
CANON
INC.
CANON
PC72074017501710
REIM
AUG.1994
PRINTED
IN
JAPAN
omPFumt
AU
JAPONI