Ricoh FT5233 Service Manual page 83

DEVELOPMENT
6.5.6 Bias for Sensor Patterns
(1) Development bias voltage for ID sensor pattern
SP33: Black Pattern Bias
Black Toner
Data
Density
0 Normal
1 Lighter
2 Darker
3 Darkest
SP75: Red/Blue/Green Pattern Bias
Color Toner
Data
Density
0 Normal
1 Lighter
2 Darker
3 Darkest
The development bias voltage for the ID sensor patterns (both Vsg and Vsp)
are shown in the above table. They differ depending on color because the
relation between the reflected light intensity and developed sensor pattern
density is different from color to color. The difference of development bias
voltage for each color's ID sensor pattern compensates them.
The development bias voltage for ID sensor pattern is –20V more for the first
500 copies than that for the rest. This is to compensate a tendency of the
developer to have a slightly higher toner density until it stabilizes.
The toner density can be adjusted by changing the setting of SP33 for black
and that of SP75 for color, as shown in the table.
(2) Development bias voltage for V
The development bias voltage for non-image area is applied to the bare
drum where Vrg output is sampled.
0V is applied for the V
the process control section.
(3) Development bias voltage for V
The base development bias voltage (VB0–20V) for the V
Vlg and Vlp) is decided in the process of the initial V
The actual bias voltage for the V
Development Bias Voltage for
ID sensor Pattern
0~500 501~
–220V –200V
–180V –160V
–240V –220V
–260V –240V
Development Bias Voltage for ID sensor Pattern
0~500
Red/Blue Green
–200V –240V
–160V –200V
–220V –260V
–240V –280V
R
pattern which gives Vrp output, as explained in
R
pattern
L
L
Red/Blue
–180V
–140V
–200V
–220V
pattern
pattern has some corrections.
2-54
12 February 1992
501~
Green
–220V
–180V
–240V
–260V
pattern (both
L
pattern detection.
L