Fig. 4-19 Exposure Mask Removal - Canon NP-70 Service Manual

NP•70
4-15
4) EXPOSURE MASK
The center portions of the fluorescent lamps radiate a slightly greater amount of light than
the ends and the lens unit enhances this action by passing more light through its center than
through its edges. Thus, the exposure mask is necessary to minimize these differences by illu-
minating the drum surface equally from one end to the other —the central light is decreased in
intensity by a narrowing of the slit, and the light from both ends is increased by a widening
of the slit.
5) MIRROR/LENS UNIT
This unit is attached to the end of the chamber &its specifications are as follows:
Focal distance (f)
Maximum aperture (F)
Magnification
Resolution
180 mm
1 :4.5 (variable to F9)
1 1
more than 10 lines/mm
6) EXPOSURE ADJUST LINE
This line is made of polypropylene with a diameter of 0.4 mm. Its length is 118 cm, when
tied to the hooks of its tension spring, and connects the exposure dial to the diaphragm
mechanism of the lens unit. These control the light intensity to the photosensitive surface
of the drum unit.
4.3-3 REMOVAL/INSTALLATION ACTIONS
The Optical Assembly and Lens Unit should never be removed from the NP-70 for any
reson. This is due to the critical allignment necessary for proper machine operation. However,
the following main component replacements are possible.
1) EXPOSURE MASK REPLACEMENT
a) Open the front left access door.
b) Remove the A. C. Corona Assembly from the copier.
c) Grasp the front end of the mask and draw the mask out of the copier.
Fig. 4-19 Exposure Mask Removal
d) Repeat a) ^~ c) in reverse order for installation.
© CANON INC.
Second Printing,lune, 1974