CANON NP1010
Service Manual

F. 1.

Measuring Outline

the Document

Density

The copier is equipped with an automatic density control (AE) mechanism, which controls the DC component of the developing bias to suit the density of the document. As long as the document is uniform overall, copies free of fogging can be made by varying the DC component of the developing bias. The AE sensor is mounted inside the lens unit and consists of a photodiode and operation amplifier. 2. Mechanism

During the initial rotation (INTR), the scanning lamp goes ON, and the scanner moves forward about 12 cm and reverses. The microprocessor on the DC controller, while the scanner moves in reverse, reads the output of the AE sensor 80 times at intervals of 1 mm. The area measured at the time is as shown in Figure 3-20.

Remove the upper front cover, and close the, copier. Turn the power ON, and open the delivery unit cover. Place a blank sheet of paper (copy paper) on the copyboard, and close the document cover. Hold the REDUCTION/ENLARGEMENT and ZOOM MODE keys down, and close the delivery unit cover. . The copier enters the AE adjustment mode. . The count is �00�. 6) Select the DIRECT copy mode, and press the COPY START key. * The scanning lamp goes ON, and the scanner moves forward to the copy paper. . The count indicates the output of the AE sensor read by the microprocessor. 7) Turn VRIOI on the DC controller until the count is �55�. Note: The problem detection circuit of the lamp regulator will be activated if the scanning lamp remains ON for 15 to� 30 seconds to turn the lamp OFF. If the lamp goes OFF before the count indicates �55�. turn the power OFF and ON, and repeat step 3) and onward. 8) 9) Note: Press the CLEAR/STOP key. Turn the power OFF and ON.

�-_

1
100mm

Figure 3-20

Area

Measured

See Figures 3-21 and 3-22 for the relationship between the count indication and the input of the microprocessor or the DC component of the developing bias.

The microprocessor calculates the average of the density data of the 80 points and controls the DC component of the developing bias based on its result.

5v

3.

Adjustment ov

The following adjustment is performed when the DC controller or AE sensor is replaced. 1) Turn the power OFF, open the copier, and remove the drum unit.

Figure 3-21

Figure 3-22

. .

Cover the drum

as soon prints

as it is out of or scratches

Do not leave finger

3-18

COPYRIGHT

01988

CANON

INC.

CANON�NP-1010

AEY.0 OEC. 1988

PAINTED

IN JAPAN IIMPAIME

AU JAPDN)