Service manual

1-4-19
2AV/X
Description
Maintenance
item No.
1-4
U091 Checking shading
Description
Performs scanning under the same conditions as before and after shading is performed, displaying the
original scanning values at nine points of the contact glass.
Purpose
To check the change in original scanning values before and after shading. The results may be used to
decide the causes for fixing unevenness (uneven density) of the gray area of an image: either due to optical
(shading or CCD) or other problems.
Also to check the causes for a white or black line appearing longitudinally.
Method
1. Press the start key. The screen for selecting an item is displayed.
2. Select the item to be operated using the cursor up/down keys. The selected item is displayed in reverse.
Display
SHD BEFORE
SHD AFTER
Output list
Performs scanning before shading and displays the result.
Performs scanning after shading and displays the result.
3. Press the start key. Scanning is performed under the selected conditions and the result is displayed.
When scanning is performed before shading, the scan value at the machine center should be slightly
different from those at the machine front and rear. When scanning is performed after shading, there
should be no difference between respective values. Any differences between the values at machine front
and rear indicates that scanner problem causes the fixing unevenness.
If the displayed results indicate no shading problems, the fixing unevenness (uneven copy density) is
caused by factors other than in the scanner section (shading or CCD).
If a black line appears, the cause may assumed to be based on the results of the scanning operation
before shading: if a white line appears, they may be assumed based on the results of the scanning
operation after shading. Note that depending on the thickness and location of the black or white line, it
may not be possible to use this method to determine the cause. This is because the displayed values
obtained from scanning at the limit of nine points are insufficient to provide significant information.
011 024 015
001 000 000
004 004 000
20 mm from the machine left
200 mm from the machine left
400 mm from the machine left
Machine center
100 mm from the machine
center toward machine front
100 mm from machine
center toward machine rear
Figure 1-4-4
4. Press the stop/clear key. The screen for selecting an item is displayed.
Completion
Press the stop/clear key. The screen for entering a maintenance item is displayed.