Hitachi HT-4139-28 Maintenance Manual page 53

REV0 2010.02.15
7.8.4.5 Hardware
NOTE: Recognize 11 marks at the edge of sheets and display the reference value (reference
coordinate) and the measurement (sensor coordinate)
At recognition of characters it will be used for correction of distortion.
If result is "NG" (failed),
(1) Judge from the measurement results.
When both side are measured at the same time, to confirm which side has
the issue and check if the sheets are normal. Repeat scanning multiple
times.
Confirm the images.
(2)
Get images with the reading test of the maintenance menu or
Video image display 2.
Cleaning the optical systems
(3)
If image is abnormal at (2), clean the lower mirror, cover sheet,
and the scanner assy.
7.8.4.6 Paper feeding speed
NOTE: Recognizing the 11 marks in the Fig.4 and calculate the speed difference between the reference
value and measurement results and get the speed correction value.
Result +: Paper feeding speed is faster
Result -: Paper feeding speed is slower
If result is "NG" (failed),
(1) Clean the T1 roller. Check if there is any part where paper might be jammed in the paper feeding
mechanism.
In case of (+): Paper feeding speed is faster. Roller maybe has become thicker because of contamination.
In case of (-): Paper feeding speed is slower, abnormal paper feeding, paper slip。
(2) Confirm the images.
Get images with the reading test of the maintenance menu or Video image display 2.
(3) Cleaning the optical systems
If image is abnormal at (2), clean the lower mirror, cover sheet, and the scanner assy.
(4) If (3) can not fix the problem, replace the scanner ASSY and the MAIN_P/K__ASSY.
Abnormalities of image are caused by contamination at the reading part and the scanner assy.
-H7-20-
[Hardware surface and back]
Information for correction of
CCDSensor optical systems.
Fig. 4 Position of mark recognition
[Feeding speed]
Speed correction range of the Paper feed motor
Correction range: ±1.0%
distortion of the