Canon PC720 Service Manual - Page 66

density correction

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MEIOPERATIONS AND TIMING ,,,,,w,:m.k- ;,.onw44.0.. 4. Controlling the Voltage Level of the DC Bias to Suit the Copy Density Setting The copier varies the DC bias control signal (DCBPWM) according to the settings shown below to vary the DC component voltage, thereby controlling the copy density. • setting of the density adjusting lever (manual control mode) • output of the AE sensor (automatic control mode) • type of developing assembly Type of developing assembly DC bias Black -80V to -550V Color -115V to -580V The density correction switch (SW101) on the DC controller PCB may be set to either of the three settings by the user, selected to correct foggy images caused by changes in the sensitivity of the photosensitive drum. The density correction switch (SW101) functions when the density is adjusted in manual mode or during automatic density adjustment mode. 0 .miera cts 'qA Figure 3-309 See Figures 3-310 through -313 for changes in the DC bias according to the setting of the density adjusting lever in manual mode and to the changes in the AE sensor output in automatic mode. 3 - 26 COPYRIGHT @ 1994 CANON INC. CANON PC72017401750/770 REV.O AUG.19M PRINTEDIN JAPAN pout AU JAPON)

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MEI
OPERATIONS
AND
TIMING
,,,
,
,w
,
:m
.
k
-
;,
.onw44.0..
.miera
cts
4.
Controlling
the
Voltage
Level
of
the
DC
Bias
to
Suit
the
Copy
Density
Setting
The
copier
varies
the
DC
bias
control
signal
(DCBPWM)
according
to
the
settings
shown
below
to
vary
the
DC
component
volt-
age,
thereby
controlling
the
copy
density.
•
setting
of
the
density
adjusting
lever
(manual
control
mode)
•
output
of
the
AE
sensor
(automatic
control
mode)
•
type
of
developing
assembly
Type
of
developing
assembly
DC
bias
Black
-80V
to
-550V
Color
-115V
to
-580V
The
density
correction
switch
(SW101)
on
the
DC
controller
PCB
may
be
set
to
either
of
the
three
settings
by
the
user,
selected
to
correct
foggy
images
caused
by
changes
in
the
sensitivity
of
the
photosensi-
tive
drum.
The
density correction
switch
(SW101)
functions
when
the
density
is
adjusted
in
manual
mode
or
during
automat-
ic
density
adjustment
mode.
0
'qA
Figure
3-309
See
Figures
3-310
through
-313
for
changes
in
the
DC
bias
according
to
the
set-
ting
of
the
density
adjusting
lever
in
manual
mode
and
to
the
changes
in
the
AE
sensor
output
in
automatic
mode.
3
-
26
COPYRIGHT
@
1994
CANON
INC.
CANON
PC72017401750/770
REV.O
AUG.
19M
PRINTED
IN
JAPAN
pout
AU
JAPON)