Canon CP660 Service Manual page 177

5. Cassette 1 Last Sheet Detection
The printer unit is capable of detecting the last sheet from the cassette 1. The feed-
ing distance from the cassette 1 paper absent sensor to the registration roller is short; as
such, if the last sheet was picked up during continuous printing, writing would start before
the DC controller PCB identifies the absence of paper, requiring the printer unit to detect
the absence of paper before writing starts and, ultimately, to prevent soiling between the
photosensitive drum and the intermediate transfer drum.
The cassette 1 last sheet sensor (PS29) is a reflecting type sensor, and consists of a
light-emitting section and a light-receiving section. In the presence of paper, the light from
the light-emitting section will be reflected by the paper to reach the light-receiving sec-
tion. In the absence of paper (after the last sheet has been picked up), on the other hand,
the light from the light-emitting section will pass through the machine's inside, not reach-
ing the light-receiving section.
In response, the DC controller PCB will assume that the last sheet has been picked
up, and communicate the fact to the printer board*
1
* Reader controller PCB (when making prints with the reader unit installed).
One Sheet Exists in the Cassette 1
No Sheet Exists in the Cassette 1
COPYRIGHT © 1999 CANON INC.
Download free service manual at http://printer1.blogspot.com
Last sheet
Cassette 1 last sheet sensor (PS29)
Figure 5-212
CANON 660/2100 REV.0 FEB. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
CHAPTER 5 PICK-UP/FEEDING SYSTEM
1
to stop writing of the next image.
Pick-up roller
5-15