Canon PC720 Service Manual - Page 71

Measuring, Density, Original

Get Canon PC720 PDF manuals and user guides View all Canon PC720 manuals
Add to My Manuals
Save this manual to your list of manuals

Page 71 highlights

OPERATIONS AND TIMINGEll G. Measuring the Density of the Original (AE) 1. Outline The copier is equipped with an automat- ic density adjustment (AE) mechanism which adjusts the DC component of the developing bias. As long as the original has an even overall density, the AE mechanism ensures the generation of copies without fogging by varying the DC component of the developing bias to suit the density of the original. The copier's AE mechanism does not execute an AE scan; rather, it measures the density of the original during initial rotation at the scanner home position; for this reason, the copying speed remains the same in both AE and non-AE modes. Figure 3-316 shows the circuit that con- trols the measurement of the density of origi- nals. AE sensor // Scanning lamp Copyboard glass // // // AE sensor 0 Photosensitive Developing w drum cylinder Microprocessor AE signal VR103 Developing DC bias Developing DC bias on signal (DVDCON) Microprocessor DC bias control circuit Developing DC bias control signal (DCBPWM) Composite power supply PCB Amplifier circuit DC controller PCB Figure 3-316 COPYRIGHT © 1994 CANON INC. CANON PC72G7401750770 REV.0 AUG.1994 PRINTED IN JAPAN pivot AU JAPON) 3 - 31

  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10
  • 11
  • 12
  • 13
  • 14
  • 15
  • 16
  • 17
  • 18
  • 19
  • 20
  • 21
  • 22
  • 23
  • 24
  • 25
  • 26
  • 27
  • 28
  • 29
  • 30
  • 31
  • 32
  • 33
  • 34
  • 35
  • 36
  • 37
  • 38
  • 39
  • 40
  • 41
  • 42
  • 43
  • 44
  • 45
  • 46
  • 47
  • 48
  • 49
  • 50
  • 51
  • 52
  • 53
  • 54
  • 55
  • 56
  • 57
  • 58
  • 59
  • 60
  • 61
  • 62
  • 63
  • 64
  • 65
  • 66
  • 67
  • 68
  • 69
  • 70
  • 71
  • 72
  • 73
  • 74
  • 75
  • 76
  • 77
  • 78
  • 79
  • 80
  • 81
  • 82
  • 83
  • 84
  • 85
  • 86
  • 87
  • 88
  • 89
  • 90
  • 91
  • 92
  • 93
  • 94
  • 95
  • 96
  • 97
  • 98
  • 99
  • 100
  • 101
  • 102
  • 103
  • 104
  • 105
  • 106
  • 107
  • 108
  • 109
  • 110
  • 111
  • 112
  • 113
  • 114
  • 115
  • 116
  • 117
  • 118
  • 119
  • 120
  • 121
  • 122
  • 123
  • 124
  • 125
  • 126
  • 127
  • 128
  • 129
  • 130
  • 131
  • 132
  • 133
  • 134
  • 135
  • 136
  • 137
  • 138
  • 139
  • 140
  • 141
  • 142
  • 143
  • 144
  • 145
  • 146
  • 147
  • 148
  • 149
  • 150
  • 151
  • 152
  • 153
  • 154
  • 155
  • 156
  • 157
  • 158
  • 159
  • 160
  • 161
  • 162
  • 163
  • 164
  • 165
  • 166
  • 167
  • 168
  • 169
  • 170
  • 171
  • 172
  • 173
  • 174
  • 175
  • 176
  • 177
  • 178
  • 179
  • 180
  • 181
  • 182
  • 183
  • 184
  • 185
  • 186
  • 187
  • 188
  • 189
  • 190
  • 191
  • 192
  • 193
  • 194
  • 195
  • 196
  • 197
  • 198
  • 199
  • 200
OPERATIONS
AND
TIMING
Ell
G.
Measuring
the
Density
of
the
Original
(AE)
1.
Outline
The
copier
is
equipped
with
an
automat-
ic
density
adjustment
(AE)
mechanism
which
adjusts
the
DC
component
of
the
developing
bias.
As
long
as
the
original
has
an
even
overall
density,
the
AE
mechanism
ensures
the
generation
of
copies
without
fogging
by
varying
the
DC
component
of
the developing
bias
to
suit
the
density
of
the
original.
0
w
AE
sensor
The
copier's
AE
mechanism
does
not
execute
an
AE
scan;
rather,
it
measures
the
density
of
the
original
during
initial
rotation
at
the
scanner
home
position;
for
this
reason,
the
copying
speed
remains
the
same
in
both
AE
and
non
-AE
modes.
Figure
3-316
shows
the
circuit
that
con-
trols
the
measurement
of
the
density
of
origi-
nals.
Copyboard
glass
//
//
//
//
Scanning
lamp
Microprocessor
AE
sensor
Photosensitive
drum
Developing
cylinder
Developing
DC
bias
Developing
DC
bias
on
signal
(DVDCON)
AE
signal
VR1
03
Amplifier
circuit
DC
controller
PCB
Figure
3-316
Microprocessor
DC
bias
control
circuit
Developing
DC
bias
control
signal
(DCBPWM)
Composite
power
supply
PCB
COPYRIGHT
©
1994
CANON
INC.
CANON
PC72G7401750770
REV.0
AUG.1994
PRINTED
IN
JAPAN
pivot
AU
JAPON)
3
-
31