2. OperationThe DC controller PCB measures the outputs of the original detection circuits atintervals of 0.2 sec until the Copy Start key is pressed or for 15 sec after the copyboardcover open/closed sensor (PS5) has turned on while the copyboard cover is beingclosed.Figure 3-402If an original exists over a sensor, the original detection circuit receives the lightreflected by the original so that the output of the detection circuit remains the sameregardless of the angle of the copyboard cover.If no original exists over the sensor, on the other hand, the output of the detectioncircuit immediately after PS5 turns on is small. When the copyboard cover is fully closedthereafter, the light reflected by the detection circuit receives the light reflected by thecopyboard sheet, and the output will be larger.Accordingly, the DC controller will assume the presence of an original if the output ofthe detection circuit remains the same, while assuming the absence of an original if theoutput changes.This type of detection enables identification of the size of even a black original.Reference:1. If the original is thick and, as a result, the copyboard cover will not fully close afterPS5 has turned ON, the level of the sensor output will not change regardless ofthe size of the original. If none of the levels (of the three sensors) does notchange, the DC controller identifies the size of the original by comparing themeasurement taken when PS5 has turned on against the slice level.2. If the copyboard cover is opened (PS5 is off), the cassette containing themaximum size paper will be selected. DC controller PCBOutputOriginaldetectioncircuitPS5 ONOriginalCopyboard cover30° (approx.)(The thickness of the output arrow represents the size of the level.) OutputPS5 ONDC controller PCBOutput(constant)Output(varied)COPYRIGHT © 1997 CANON INC. CANON NP6350/NP6251 REV. 0 JULY 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)CHAPTER 3 EXPOSURE SYSTEM3-21Download service manual and resetter printer at http://printer1.blogspot.com
