Canon CP660 Service Manual page 41

Step 7 (secondary transfer)
In this step, the toner on the intermediate transfer drum is transferred to paper, which
is forced against the intermediate transfer drum by the secondary transfer belt assembly
pushed up by the secondary transfer belt cam.
In this step, continuous application of a positive bias on the secondary transfer belt
causes the surface of the belt to take on a negative potential, possibly leading to sepa-
ration faults if left unattended. To prevent faults, a negative DC bias is applied at the end
of secondary transfer for removing charges from the belt.
During multiple initial rotation, a negative DC bias is applied to prevent soiling the
back of paper; i.e., the toner adhering to the surface of the secondary belt is returned to
the intermediate transfer drum.
To prevent excessive increases of charges on the transfer belt caused by continuous
application of positive DC bias on the secondary transfer belt, a negative DC bias is
applied to the separation charging assembly to remove charges from the belt at the end
of secondary transfer.
Secondary transfer
belt assembly
COPYRIGHT © 1999 CANON INC.
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Intermediate transfer drum
Figure 1-810
CANON 660/2100 REV.0 FEB. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
CHAPTER 1 GENERAL DESCRIPTION
Paper
DC bias
1-29