Canon imageRUNNER 330 Service Manual page 96

CHAPTER 4 IMAGE FORMATION SYSTEM
c. Photosensitive Drum Resistance
The surface coating of the photosensitive drum tends to become worn over time, causing its
photosensitive medium to become thinner and, ultimately, affecting its charging characteristics. To
ensure the production of stable image, the resistance is measured and the density correction curve is
varied according to the result of measurement.
The surface of the photosensitive drum is charged to a specific voltage (AC + DC).
Application current values are sampled while charging takes place to compute the resistance
of the photosensitive drum.
The resistance is checked at such times as shown below:
• During initial rotation after the Copy Start key is pressed.
• During initial rotation after the front door is opened and closed (other than for jam
removal).
• During initial rotation after the control panel power switch is turned on.
• During initial rotation after making 500 copies/prints.
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COPYRIGHT © 1999 CANON INC. CANON imageRUNNER 400/330 REV.0 JAN. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
Copy density
Coating
is thin.
Density
correction curve
Figure 4-308
Coating
is thick.
Original density