Canon iR C6800 Series Service Manual page 940

Chapter 13
13.3.4.3.2 Frequent DF Reading Glass Cleaning Message
The following is a list of causes and field remedies associated with the symptom:
Cause
A. dust or dirt on the reading glass; the reader unit detects dirt to issue the cleaning message, and it does not detect
stray dust
B. dirt on the read roller, or dirt on the white plastic film
C. scratch on the reading glass: or dirt resisting cleaning
D. scratches in radial direction of the red roller, or dirt remaining after cleaning
E. dirt on the CCD
<Checking for Dirt on the CCD>
The presence of dirt on CCD cells will cause a line in the image in both stream reading and copyboard modes alike.
If the particles are small, the reader unit will make up for their presence, removing lines from the output image.
Set '0' to the following service mode item, and check the output image for a line; thereafter, be sure to change the
setting back to its initial value:
COPIER>OPTION>BODY>DFDST L1 (level 1)
Field Remedy
A. Clean the reading glass using cleaning tissue or cleaning oil.
B. Dry wipe the read roller/white plastic film; or, use alcohol to clean them.
Memo:
If the machine is installed in a dusty place, cleaning it on a periodical basis is desirable.
C: Replace the reading glass.
D. Replace the read roller.
Memo:If you have replaced the rear roller, be sure to perform the following:
white level adjustment
DF height adjustment
E. Replace the CCD unit.
13.3.4.3.3 Frequent DF reading Glass Cleaning Message (user requesting disabling of the message)
This message is not issued in response to the presence of dirt inside the machine (i.e., it is not used to alert the user
to an error condition). Nevertheless, if the user requests disabling the message, go through the following:
Field Remedy
A. Change the level used to detect dust.
Decrease the level of detection (level 1) in service mode: COPIER>OPTION>BODY>DFDST L in increments of '5'.
Memo:
A decrease in the level will decrease the level of correction executed for the presence of dust, possibly leaving a light
black line in the output image. Setting it to '0' will disable dust detection all together.
B. Change the setting of the cleaning message in service mode:
COPIER>OPTIONAL>BODY>DFDST L1 (level 1).
Memo:
The cleaning message may be disabled in service mode, but the machine will still check for dust; varying the read
position according to the result of detection.
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