Ricoh FT8680 Service Manual page 33

31 July 1995
1.3.6 Vr Measurement
Drum
Potential
The drum residual voltage (Vr) tends to increase during the drums life due to
electrical fatigue. The residual voltage cannot be reduced even if the
exposure lamp voltage is increased. Therefore, the Vr change has to be
compensated by other means.
The main PCB checks the drum potential just after the erase lamp exposure,
by the drum potential sensor during drum conditioning. The drum potential is
in fact Vr. This measured Vr is used as the standard for the following other
compensations.
1. Vd Correction
2. V Correction
L1
V
0
Vd
Original Density
Dark
2-9
PROCESS CONTROL
V
L
Vr
Light
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