Theory of Operation 2-11
High Area Coverage Mode
The High Area Coverage mode delays page feeding giving the printer additional time
to dispense toner. This mode compensates for images whose toner density exceeds the
printer’s toner dispense capabilities. This typically occurs during continuous runs of
images that drop the toner density for any color Developer below the reference value.
Admix Mode
If High Area Coverage mode fails to compensate for the reduction in Developer toner
density, or if the printer is moved to an environment with a different humidity level
changing the reference value, Admix mode dispenses toner immediately to restore
toner density levels if needed.
LED Light Density CTD (ADC) Control Sensor
The CTD (ADC) Sensor is a photo-reflective sensor that emits light from an LED and
detects the reflected light returning from the Transfer Roller. The CTD (ADC) Sensor
reference voltage (reflected light density) is established when both the sensor and the
Transfer Roller are clean and free of defects. The light emitted from the LED is
controlled so that the reflected light density meets the reference value.
LED light emission control is implemented in two ways:
■ Sets the light density so that the light reflected satisfies a specific value.
■ Adjusts the subsequent light density to be within a specific tolerance value.
1. Light Density Setting
The reflected light density can vary greatly if the Transfer Roller has just been
replaced or the CTD (ADC) Sensor has just been cleaned, or is dusty with waste
toner. To compensate with this variance, the light density is reset each time the power
is turned on or a door is opened.
When the output of the CTD (ADC) Sensor does not meet the reference value, the
intensity of the LED light emissions are increased gradually and the Light Density
Setting is adjusted. If the light density is increased to the maximum and output of the
CTD (ADC) Sensor does not reach the reference value, a warning message indicates
the sensor is dirty. If the sensor output remains above the reference value, a fatal error
reports that the sensor is faulty.
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