Ricoh A151, Field Service Manual

Page: 290 / 397

8. DRUM CHARGE
8.1 GRID VOLTAGE CORRECTION
This machine does not correct drum residual voltage correction (V
R
correction) or drum wear correction.
8.2 GRID VOLTAGE FOR IMAGE DENSITY CONTROL
The main board controls the grid voltage through the CC/Grid/Bias power
pack. As the grid voltage for the image density control becomes less, the
copy image becomes lighter, and vice versa.
The grid voltage for image density is based as follows:
Grid Voltage = Standard image density grid voltage (–680 volts [SP60 = 4])
+
Auto image density level factor (SP34)
8.2.1 Standard Image Density Grid Voltage
The standard image density grid voltage (SP60) is set at the factory and the
setting is different for each machine. The setting of SP60 is printed on the SP
mode data sheet located inside the inner cover of the machine.
8.2.2 Auto Image Density Level Factor (SP34)
Auto image density level Data (SP34) Change of grid voltage (volts)
Normal 0 *
±
0
Darker 1 –40
Lighter 2
±
0
* Factory setting
The grid voltage and the exposure lamp voltage are constant regardless of
the output from the auto image density sensor. Only the development bias
voltage varies depending on the output from the auto image density sensor.
When the auto image density level data in SP34 is set to darker, the grid
voltage is changed –40 volts as shown in the above table. When it is set to
lighter, the grid voltage does not change. However, the development bias
voltage is corrected.
DRUM CHARGE
A202/A203 8-12 SM