Ricoh PRIPORT VT 2000 Series Service Manual page 58

2.5.7 Printing Density Change
VT2100/VT2130/VT2150 Circuit in Line mode:
Shading Distortion
Memory Correction
Signal
Selector 1
Output
Black Date
Correction
(Terminal No.)
MANUAL 1
MANUAL 2
Standard
MANUAL 3
The printing density can be changed by the printing density switch when in
the line mode. This switch changes the threshold level to 47 %, 67 %, or 73
% of the white level.
The selected threshold level enters port V
corrected image signal enters port V
In manual printing density mode (Dark, Darker, and Lighter), the A/D
converter outputs either all "H" BAD signals (4 bit) or all "L" BAD signals (4
bit). This is determined by the LUF signal
When the image signal is lower than the threshold level, the LUF signal is
output from the A/D converter to make all BAD signals "H". Then the image
signal is output as a black.
When the image signal is higher than threshold level, LUF signal is not
output. Then the BAD signals are all "L".
3
3
73%
67%
47%
1.7V
A/D Converter
CN606
SW ON
-2
1-2 H
2-3 H
---- H
4-5 L
Image Signal
VS
VH
A/D
Converter
VL
LUF
5V
Selector 3
3
A
5
B
6
C
COM
1
Selector 3
-3 -5
H L COM--3
L H COM--5
H H COM--1
H H COM--6
while the shading distortion
L
of the A/D converter.
H
2-31
28 February '91
4 bit
Gate
Image
Signal
5
CN606-2
3
CN606-3
Printing
1
CN606-5
Density
S.W.
2
CN606-1
4
CN606-4
4 bit
Image
Signal