Ricoh Robin Service Manual page 47

DEVELOPMENT
5.4.1 Base Bias Voltage Factor In Manual Image Density Mode
Manual ID Level
Base Bias Voltage (volts)
Exposure Lamp Data
Vo: Exposure Lamp Data for ID level 4 (SP48)
In manual ID mode, the base bias voltage depends on the manually selected
ID level. The voltage applied at each ID level is shown in the above table.
The base exposure lamp voltage also varies depending on the manual ID
level as shown in the table.
*Note: The base bias voltage at ID level 7 can be changed using SP50 as
follows.
Image density
Normal
Darker
Lighter
Lightest
5.4.2 Base Bias Voltage Factor In Automatic Image Density Mode
In auto image density mode, the base exposure lamp voltage is fixed at Vo
(SP48). Image density is controlled by changing only the base bias voltage.
The base bias voltage depends on the background image density of the
original, which is measured using the auto ID sensor. (See page 2-16 for
more information.)
The CPU checks the voltage output from the automatic ID circuit. This circuit
has a peak hold function. The peak hold voltage corresponds to the
maximum reflectivity of the original. The CPU then determines the proper
base bias level with reference to the peak hold voltage.
The table on the following page gives the base bias voltages at each ADS
output level.
When the automatic density level is set to lighter by SP34, the base bias
voltage shifts –40 volts as shown in the following table.
Darker
1 2 3
–120 –160 –160
Vo –4 Vo –4 Vo –2
Data (SP50) Bias voltage (volts)
0 –240
1 –200
2 –280
3 –320
(Factory Setting: –240 volts)
2-28
4 5 6
–160 –160 –200
Vo ±0
Vo +2 Vo+2
24 June 1994
Lighter
7
–240 *Note
Vo+4