Ricoh Aficio Color 4006, Service Manual

Page: 54 / 487

24 February, 1999 PROCESS CONTROL
2-5
Detailed
Descriptions
Step 1: V
SG
Adjustment
The type of ID sensor used in this machine responds differently for black and color,
so there are two V
SG
values, one for black toner and one for CMY toner.
The type of ID sensor used in this machine is very sensitive, and outputs some
voltage even if there is no light being reflected off the drum. This output is known
as the ‘offset’. It is about 1 V for black and about 0.2 V for color, but is different for
each sensor. For more details on this sensor (known as a ‘diffused reflection ID
sensor’), see ‘Step 4: Sensor Pattern Density Detection’.
The ID sensor checks the bare drum’s reflectivity and the machine calibrates the
output of the ID sensor as follows. This voltage is known as V
SG
:
•
Black: (1.8 + offset)
±
0.1V
•
Color: Must be between 0.2 and 3 V
This calibration compensates for the drum’s condition (due to ageing) and the ID
sensor condition, such as dirt on the surface of the drum or ID sensor.
Note that V
SG
for black is less than half that in previous models. This is due to the
new type of ID sensor.
Step 2: ID Sensor Pattern Generation
The machine makes a 16-grade pattern on the drum for
each toner color. Each grade is made by changing the
LD power. At this stage, the patterns are not developed;
they remain as latent images.
20
1st level
of LD power
2nd level
of LD power
3rd level
of LD power
15th level
of LD power
16th level
of LD power
25
20
A259A004.WMF