CANON NP6545
Manual de Servicio

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Primary Current Control To measure the dark area potential (VD) for the first time after power-on, a reference current (setting stored in ROM) is sent to the primary charging assembly, and the potential sensor is used to measure the drum surface potential. The DC controller PCB compares the measurements taken of the drum surface potential and the target potential; if the drum surface potential differs from the target value, the primary charging level control signal (HVTPC) generated by the DC controller ,PCB is corrected. In this way, the corrected current is applied to the primary charging assembly by the high-voltage transformer (HVT). The subsequent measurements are made using the previously corrected value as the reference current, thereby reducing the first copy time. Such measurement and correction are repeated as many as eight times so that the dark area potential (VD) will be as close to the target value as possible. If the potential is not within the allowance after the eighth measurement, the dark area potential will be determined using the eighth correction value. Note: I I�, I I� ) tf the potential is in excess of the control range of the target value�aftec measuring the potential eight times, the,notation�l; will be indicated for �PLMT�(upper limit flag 1� �3, ((4 of the primary current value) in service mode, (*J*). #I(, �8 8, ,I

a.

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Potential control may be disabled by �POCNT� (display mode; *4*). When done, the primary current value will be 1000 uA in text mode and 800 uA in photo mode.

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b. Controlling the Intensity of the Scanning Lamp To measure the light-area potential for the first time after power-on, the reference ON voltage (setting stored in ROM) is applied to the scanning lamp. In response, the scanning lamp exposes the standard white plate so that the reflected light is projected to the drum. The potential of the surface of the drum exposed to the light is measured by the potential sensor, and the data is sent to the DC controller PCB. The DC controller PCB compares the measurement and the target value; if the measurement differs from the target value, the intensity adjustment signal (LINT) generated by the DC controller is corrected. The subsequent measurements are taken using the previously corrected value as the reference voltage, thereby reducing the first copy time. The corrected voltages are applied to the scanning lamp by the lamp regulator. Such measurement and correction are repeated as many as eight times so that the light area potential (VLI) will be as close to the target value as possible. However, if the measurement does not fall within the allowance after the eighth measurement, the eighth correction value will be used to determine the intensity of the scanning lamp.

COPYRIGHT@

1997 CANON INC.

CANON NP6045 REV. 1 MAR. 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)

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