Canon NP6251 Service Manual page 534

Non-AE, Copy Density at 5
<Pre-Checks>
Clean the charging wire.
Check the height of the
charging wire.
Make two to three
copies of the Test
Sheet.
COPYRIGHT © 1997 CANON INC. CANON NP6350/NP6251 REV. 0 JULY 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)
<Density slope>
Is there a
NO
difference in density
between front
and rear?
YES
Is it low (light)
YES
at the rear?
NO
Turn the adjusting screw Turn the adjusting screw
at the rear of the primary at the rear of the primary
charging assembly charging assembly
clockwise, and turn the counterclockwise, and
adjusting screw at the turn the adjusting screw
front counterclockwise at the front clockwise the
the same degree (1.5 mm same degree (1.5 mm
max. each). max. each).
Turn off and then on the
machine, and make a
copy.
Note 1: If the difference still exists after turning the screw
1. 5 mm (each; a full turn causes a 0.7mm
difference), check the charging assemblies,
scanning lamp, and scanner for dirt.
Note 2: When turning the screw counterclockwise, take
care so that the wire is not 7.5mm or less in
height.
< Solid black >
Check the copy paper
and the transfer system.
Is the density
NO
of gray scale No. 1
too low (light)?
YES
Clean the standard white
plate, mirror, lens, dust-
roofing glass, scanning
lamp, reflecting plate, and
heat absorbing glass.
Turn off and then on the
machine, and make a
copy.
1
* *
Is 'VDM' 'VDT' YES
±10 V?
NO
Check the potential
control system; if
normal, replace the
YES
Is 'PLMT' '1'?
photosensitive
drum.
NO
YES
Is 'VL1M' 'VL1T'
±10 V?
Check the scanning
NO
lamp and the
potential control
system; if normal,
YES
Is 'VL1M" 'VL1T'
replace the
±10V?
photosensitive
drum.
NO
5
* *
Increase the value of
'VDT-SW'.
Turn off and on the
machine, and make a
copy.
I. MAINTENANCE AND INSPECTION
A. Image Adjustment Basic Procedure
Is the density Execute AE adjustment.
YES
of gray scale No. 10
(See p. 11-36.)
proper?
NO
Is the density
NO
of gray scale No. 10
too high (dark)?
YES
3
* *
Increase the value of Decrease the value of
'LIGHT_5'. 'LIGHT_5'.
Make a copy.
11-3