Ricoh FW830 Service Manual page 46

31 December 1992
4.6 IMAGE DENSITY SENSOR BIAS
The ID sensor bias is similar to the development bias; however, it is applied
only when developing the ID sensor pattern.
Basically, the ID sensor bias is fixed. The normal ID bias level is –200 volts,
but it can be changed using service program #18. The following table shows
the possible settings. You should clearly understand the effect of changing
the ID sensor bias. If the ID sensor bias is increased the sensor pattern will
become lighter. This will cause more toner to be added to the developer and
thus copy images will become darker and toner consumption will increase. If
the ID sensor bias is decreased, lighter images and less toner consumption
will result.
Service Program #18
Setting
ID Bias –200
A developer counter correction is applied to the ID sensor bias to
compensate for changes in the triboelectric properties of the developer as a
new developer mixture is broken in. The following table shows this correction.
Notice that the correction depends on the average Vsp/Vsg ratio as
measured during initial conditioning as well as on the developer counter. By
factoring in the initial conditioning Vsp/Vsg ratio, this correction compensates
for slight variations between different lots of developer as well as for changes
in the developer during the break-in period. After the initial conditioning, the
copy counter will display the density level (dL).
Developer Counter Correction
Initial Conditioning
dL Vsp/Vsg (%)
1 0–10
2 10–15
0 15–20
3 20–25
4 >25
NOTE: Perform the initial conditioning by SP#5 whenever the developer
mixture is replaced. As the developer counter returns to 0 at this
time, do not perform SP#5 when the drum is replaced. There is a
possibility of dLE being displayed. This means that there was on ID
sensor (Photo sensor) error during the initial conditioning. (dLE:
Vsp/Vsg > 50%, dLP: Vsp > 2.5 < Vsg)
0 1 2
–180 –240
Factory Setting
Developer Counter (A3 lengthwise = 420 mm)
0–499 Copies 500–999 Copies More than 1000
–40 V
–20 V
0 V
+20 V
+40 V
3 4
–280 –320
–20 V
0 V
0 V
+20 V
+40 V
2-27
DEVELOPMENT
0 V
0 V
0 V
+20 V
+40 V