Ricoh FW830 Service Manual page 42

31 December 1992
4.4.2 Toner Density Sensor
The toner density sensor works in conjunction with the ID sensor to control
the amount of toner in the developer mixture. It has three basic functions.
First, it controls the toner supply in case the toner density is greater than the
upper limit and the toner density is less than the lower limit. It does not matter
what the ID sensor input is. If the amount of toner in the developer is greater
than the upper limit (in this case, the toner density sensor value, Vts, is less
than 2.4 V), toner supply is prohibited. Second, it checks toner density if an
original larger than 1220 mm is copied. Third, it takes over toner density
control completely if the ID sensor becomes abnormal (=Vsp > 2.5 V or Vsg <
2.5 V).
The toner density sensor is powered by 24 volts from CN101-1 of the main
board. The sensor's sensitivity is set by the control signal applied from
CN101-3. The input signal from the sensor is applied to CN101-2. This is an
analog signal. When the toner density is at the standard level, the analog
signal is approximately 2.1 volts.
Toner Density Sensor (S2)
Control
Circuit
Coils
2-23
Main Board (PCB1)
1 CN101-1
[24V] Va
-2
2
Toner Density Sensor
3 -3
[7.0V] (Control)
-4
4
GND
DEVELOPMENT