Canon CLBP-460PS, Service Manual

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the paper within a specified period of time after detection of the ITB HOME POSITION DETEC-
TION signal (/ITBHP), the DC controller conducts the pick-up operation one more time. If the
registration paper sensor cannot detect the leading edge of the paper after the 2nd pick-up oper-
ation, the DC controller assesses a pick-up delay jam and reports it to the video controller.
b. Last paper detection
This printer can detect the last paper on the multi-purpose tray. The distance between the
multi-purpose tray paper sensor and the secondary transfer unit is short. Therefore, if the last
paper is picked-up during continuous printing, the DC controller starts writing the next image
before it detects that there is no paper on the tray.
The last paper is detected before writing the next image to prevent smearing of the photo-
sensitive drum and intermediate transfer belt.
To detect the last paper, the last paper sensor (PS3) monitors the rotation of the last paper
detection roller on the multi-purpose tray. If there are two or more sheets on the multi-purpose
tray, the last paper detection roller does not rotate when one sheet is picked up. When the last
paper is picked up, the last paper detection roller rotates, and the last paper sensor output
changes between “H” and “L”. The DC controller determines that the last paper has been picked
up and notifies the video controller of no paper on the multi-purpose tray and inhibits forma-
tion of the next image.
Figure 2-5-5
2 - 81
CHAPTER 2
Multi-purpose tray
Last paper sensor
(PS3)
Last paper detection roller
Last paper
< Last paper pick-up >
Multi-purpose
pick-up roller
The last paper detection
roller turns.
The last paper detection
roller does not turn.
< Normal paper pick-up >