Canon NP-70 Service Manual page 31

NP -70
2-5
2.3 OUTLINE OF MAIN ASSEMBLIES
2.3-1 COPYBOARD ASSEMBLY
The copyboard is the assembly on which the original to be copied is placed. It moves forward
and backward by means of two wires wound on the drive pulley and is moved by clutches
CG 1 and CL2.
2.3-2 ILLUMINATION ASSEMBLY
This assembly functions to uniformly illuminate the original on the copyboard, after which the
reflected image is projected onto the photosensitive drum. The two 25 watt lamps in this
assembly are maintained in a "warm" condition continuously by a low-level A. C. filament
voltage and a continuous high-level A. C. radiation from the electromagnetic field radiator.
Thus, when full A. C. voltage is applied to the lamp filaments, the lamps come ON instantly.
2.3-3 OPTICAL ASSEMBLY
This assembly functions to form an image of the original on the photosensitive drum, while
both image and drum move in synchronization. The assembly consists of a chamber contain-
ing a minror and a lens unit.
* Lens 180 mm, F : 4.5
In-mirror type
* Magnification:
1 1
* Maximum size of original: 297 mm x 420 mm (JIS-A3)
The tone of a copied image is adjusted by turning the exposure dial (located on the control
panel), which changes the size of the lens diaphragm.
The dial graduations are related to the lens F-number as follows:
F4. 5 9 on dial
F7.14 1 on dial
2.3-4 DRUM ASSEMBLY
This assembly contains the drum, with its photosensitive sheet covering, and the components
necessary to mount the drum in the copier.
The sheet covering on the drum has a sensitive area approximately 310 mm x 480 mm. Thus,
copying up to JIS A3-size is possible.
2.3-5 CORONA ASSEMBLIES
The coronas used in the NP-70 are the positive corona (+DC), the A. C. corona, the negative
corona (—DC), the transfer corona (+DC), and the residual charge eliminator (AC). These are
located, respectively, to the upper right, the lower left, the left of the drum and the exit of the
© CANON INC.
Second Printing~lune, 1974