Ricoh FT5233 Service Manual page 44

12 February 1992
1.6 DRUM ROTATION CONTROL
(V)
Drum
potential
Drum rotation time
Grid bias
V Correction for Sensor
(V)
G
voltage
Pattern
–600
–550
–520
–500
–500
–450
0 1 2
Drum rotation time
1.6.1 Overview
During the OPC drum's life the photo conductive layer gets worn and this
causes a drop in drum sensitivity and a decrement in the drum potential after
the drum charge.
The CPU keeps track of the drum rotation time (main motor on time) that
corresponds to the wear of the drum surface. The grid bias voltage is
increased at set intervals (V
1.6.2 V Correction
G
If drum potential decreases after the drum charge, the ID sensor pattern on
the drum becomes lighter, causing higher toner concentration in the
developer. Also, copy image density becomes slightly lighter.
To control toner density properly and to keep copy image density, drum
potential is maintained by increments of the grid bias voltage at set intervals.
(See graph above)
(H)
–580
–560
–540
37 63 88~(H)
correction).
G
Grid bias
(V)
voltage
V
G
–850
–800
–765
–750
–745
–700
0 1 2
2-15
PROCESS CONTROL
Correction for Image
–825
–805
–785
37 63 88~(H)
Drum rotation time