Ricoh A156 - Page 70

V
L
detection is done at the following times:
• Every 1000 Copies
• Forced Detection: whenever a new drum or exposure lamp is installed,
or exposure lamp voltage is adjusted, or when the optics are cleaned,
forced V
L
detection (SP3-105) must be executed. (See Service Tables -
Practical SP Mode Use Tables for the correct sequence of SP modes to
perform at this time).
Forced V
L
detection is different from the routine 1,000 copy V
L
detection,
so it is explained below in detail.
During forced V
L
detection, BL and V
REF
are determined as shown below.
NOTE: BL = Development bias used for V
L
correction.
BL starts at -50 V and -20 V is added until the value of V
LP
is appropriate.
V
L
Correction Method
During V
L
pattern detection, lamp voltage, drum charge voltage and
development bias are as follows.
•
Lamp voltage: same as during normal copying (ADS mode)
•
Drum charge voltage for the V
L
pattern: same as during normal copying
• Development bias for forced V
L
detection: BL + V
R
correction + V
BL(ID)
•
Development bias for V
L
detection every 1000 copies:
= BL + (–25 V) + V
R
correction + V
BL(ID)
V
BL
(ID) is an ID compensation factor based on the current ID correction
used for the V
SP
pattern (see Image Density Control for details on this ID
Correction). It is applied as shown in Table 12.
Table 12
ID correction 0 V –40 V –80 V
V
BL
(ID)
±
0 V
–10 V –20 V
BL= BL -20V
V
LP
/V
LG
> 0.45?
V
LP
, V
LG
detection
START: BL = -50V
BL = current BL
V
REF
= V
LP
/V
LG
NO
YES
_
SP3-105
Fig. 19
A156/A160/A162 2-22 STM