Ricoh FT 4015, Service Manual

Page: 35 / 229

5.4 DEVELOPMENT BIAS FOR IMAGE DENSITY CONTROL
The image density is controlled by changing two items: the amount of bias
voltage applied to the development roller sleeve, and the amount of voltage
applied to the exposure lamp.
Applying a bias voltage to the development sleeve reduces the potential
between the development roller and the drum, thereby reducing the amount
of toner transferred. As the bias voltage becomes greater, the copy becomes
lighter.
The method of control depends on whether the image density is manually
selected or auto image density is used.
The development bias voltage applied to the development roller sleeve has
the following factors:
Development bias voltage = Base Bias Voltage
(Manual or auto image density mode)
+
*Image Bias Adjustment Factor (SP33)
+
*Image Density Adjustment Factor (SP34)
+
Drum Residual Voltage (V
R
) Correction Factor
*NOTE: Image Bias Adjustment Factor (SP33) is applied for manual ID mode
only.
Image Density Adjustment Factor (SP34) is applied for ADS mode
only.
Det
ailed
Descript
ions
20 December 1996 DEVELOPMENT
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