Xerox Phaser 6280 Service Manual page 117

Phaser 6280 Color Laser Printer Service Manual
ADC Sensor Adjustment
The ADC Sensor is a reflection type sensor that radiates light from its LED
onto the target and detects the reflected light at its photoreceptor and outputs
electric signals responsive to the amount of the detected light.
To ensure an accurate patch density measurement, the surfaces of the ADC
sensor is cleaned to remove soil due to toner, etc...., and the light amount
adjustment is made so that the reflected light amount satisfies the prescribed
value, when creating the patch for potential control and toner density control.
The surface is cleared by actuating the ADC Solenoid, which causes the ADC
Pad to wipe the lens on the ADC Sensor.
LED Light Quantity Control of ADC Sensor
The ADC Sensor is a reflection type sensor that radiates light from its LED
onto the target and detects the reflected light at its photoreceptor and outputs
electric signals responsive to the amount of the detected light. For exact
density measurement, the sensor output value (reflected light intensity) must
be the specified value when no toner is put on the Belt as an objective. The
reflected light intensity varies, depending on the Belt surface condition or dirty
condition of the ADC Sensor surface. The light intensity emitted from the LED
is controlled so that the reflected light intensity satisfies the specified value.
This control is made in two ways, one to set the light intensity so that the
reflected light quantity satisfies the specified value, and the other to adjust the
subsequent light intensity to be within the tolerance.
1. Light Intensity Setting
The reflected light intensity may vary largely, if the Transfer Unit was
replaced or the ADC Sensor was cleaned. Assuming this fact, the light
intensity is set when the power is turned On, or the Front Cover is opened
and closed.
The light intensity of the LED is increased gradually, and the set value is
fixed when the output of the ADC Sensor exceeds the specified value.
2. Light Intensity Adjustment
At the execution of ADC, the light intensity adjustment is made
immediately before the patches for toner density control are generated.
The LED outputs the current setting of light intensity to check the output
value of the ADC Sensor for the specified range. If the output value is low,
the light intensity is increased by the specified amount at the next ADC, or
if high, the light intensity is reduced at the next ADC.
Theory of Operation
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