Ricoh FT6645 Service Training Manual page 80

4.4.2 Bias Control In Copy Cycle
The bias output is determined by five factors.
The total bias is described as;
ADS Mode:
Manual ID Mode:
V : Total bias
B
V : Base bias
BB
V : ADS Compensation
BA
V : User Tool mode ID Selection Compensation
BU
V : Magnification Compensation
BMG
V : Manual ID Selection Compensation
BM
1) Base Bias (V
BB
As explained in the process control section, the base bias for development is
determined by the residual voltage (V
initial setting.
V = V + (–220)
BB R
2) ADS Compensation (V
V
BA
(negative)
According to the original background density, the bias is compensated. The
compensation value is determined with the voltage measured by the ADS
sensor (ADS sensor output: V
V = 234 x (V
BA ADS
NOTE: V has a limited range from 0 V to –300 V.
BA
STM
V = V
B BB + VBU
V = V + V
B BB BU
)
[V]
V
Drum
Potential
Dark
)
BA
–300
0
Dark
) as follows:
ADS
–2.3)
2-49
+ V + V
BMG BA
+ V + V
BMG BM
D
V
L
V
R
Original Density
) measured in process control data
R
1.02 V
1 2
1 2
V (V)
ADS
V
BB
Light
2.3
2.7
Light
FT6645/6655/6665