Ricoh C211 Service Manual page 428

6-2. Printing Density Change
(950)
(830)
Shading Distortion (Vo) G VM
Black Level (1 ,7V)
Image Signal
Signal
I
a
Selector 1
output
Black Date
Correction
Shading Distortion
*
Memory Correction
:-3--- -n:
Vs
1~
I
o
VH
I
I
I
I
I
A/D
o
4 bit
I I
Image
I
I
Converter Signal
i
I
13
I
I
~;
= vL LUF
l-. .— --
I
0
4 bit
Image
Signal
I
5y
r ~ ;:
)
Selector 3
730/0— 3A
CN606-2
5
>
CN606-3
.-
670/o— 5B
3C z
c
47%o- 6C
CN606-5 10 ~
,g ~
1.7V
CN606-1 2
E .-
— COM
. CN606-4 4 c
II
I
1
I
LL&_J
1
J
J
A/D Converter
'w'N
I-5!3%
'e'ector'
-
MANUAL 1 1-2 H H L COM-3
MANUAL 2
2-3 H
L H
COM-5
Standard
H H H COM-1
MANUAL 3 4-5 L H H
COM-6
The printing density can be changed by the printing density switch when in the line
mode. This switch changes the threshold level to 47!Z0,67!!40,or 73% of the white
level.
The selected threshold level enters port
VL
while the shading distortion corrected image
signal enters port
VH
of the
A/D
convertor.
When the image signal (VS) is lower than the threshold level (VL), the LUF signal is
output from the A/D converter to make all BAD (Buffered A/D Converter) signals "H".
Then the image signal is output as a black.
—
When the image signal
(Vs) is
higher than the threshold level (VL), the LUF signal is
not output. Then the BAD signals are all "L".
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