Ricoh FT8680 Service Manual page 38

PROCESS CONTROL
1.4 COMPENSATIONS DURING COPY CYCLE
During continuous copying, the drum sensitivity changes due to the electrical
fatigue. The drum sensitivity also changes during rest time.
The following compensations are used for the drum sensitivity changes in the
copy cycle:
V
1.4.1 VL Compensation
The drum light potential (V
To get constant image quality in continuous copy runs, the development base
bias is compensated during the copy cycle.
At the beginning of each original scanning, the V
developed on the drum. The main PCB monitors the drum potential (V
the latent image of the V
and adjusts the development base bias.
See development bias section for details.
Development Base Bias:
V = V + 280 –
BB L2
∆
V = V – Vr (Maximum
L2
NOTE: N is the setting for the exposure lamp adjustment in the SP mode.
M is the setting for the Latent Image Adj. in SP mode.
Pattern
L
Drum
Potential
A171D508.wmf
) is changed during the copy cycle.
L
sensor pattern through the drum potential sensor,
L
∆
V + 10 N – 15 M
∆
V = 210, Minimum
V
0
Vd
Dark
Original Density
sensor pattern is
L
∆
2-14
31 July 1995
V
BB
V
L
Vr
A171D510.wmf
) of
L2
V = 110)
Light