Ricoh FT7770 Service Manual page 86

30 April, '89
- Toner Density Control -
The image density sensor checks the density of the sensor pattern image
once every 5 copy cycles.
from the sensor: the value for the bare drum (Vsg) and the value for the sen-
sor pattern (Vsp)
whether or not more toner should be added,
When the image density is too low, the CPU activates the toner supply sole-
noid to add a selected amount of toner over the next 5 copy cycles.
When in SP mode, the ID sensor output can be displayed in the liquid crystal
display, and VR203 on the main board can be used to adjust the intensity of
the sensor LED.
Abnormal Conditions
Under the following conditions,
operation panel.
Condition 1:
Condition 2:
Condition 3:
SP 29 displays the voltage level.
in the following table.
sensor. These are used only to determine whether condition 1, 2, or 3
exists.
Condition 1
(Vsg is selected by W #2-3
The CPU receives two voltage values directly
These two values are then compared to determine
o
High image density (no toner is added)
Low image density (toner is added)
Copies can still be made.
Vsg is less than 2.5 volt,
Vsg is O volt.
Vsp is greater than 1,4 volt.
These are not actual voltage reading from the ID
Condition 2
and VSp is selected by W
the wrench mark will being flushed in the
The condition and voltage level are given
Condition 3
2-30
#2-4.)