Controlling The Blank Exposure Lamp; Outline - Canon NP7160 Service Manual

CHAPTER 4 IMAGE FORMATION SYSTEM
F. Controlling the Blank Exposure Lamp

1. Outline

The blank exposure lamp is an LED array (40 built-in LEDs), and its activation is controlled
by a static method.
All LEDs of the blank exposure lamp are turned on while the photosensitive drum is rotating
and, in addition, the scanner is not exposing an original so as to prevent adhesion of excess toner
to the photosensitive drum. (The farthest LED (each at front and rear) is kept on at all times as
long as the photosensitive drum is rotating.)
The charges on the photosensitive drum are removed in appropriate widths according to
reproduction ratios and paper sizes while the scanner is exposing an original, thereby preventing
adhesion of unwanted toner.
The copier turns on/off the ten LEDs at the center using the blank exposure lamp center
activation signal (BLK_CNDR*), and controls the 15 LEDs (each at front and rear) by means of
serial data communication using the following signals:
• blank exposure lamp serial data signal (BLK_SD)
• blank exposure lamp serial data clock signal (BLK_SCK)
• blank exposure lamp serial data latch signal (BLK_LCK)
• blank exposure lamp drive enable signal (BLK_DEN*)
• blank exposure lamp power supply line (BLK_PW)
DC controller PCB
J101
+24V
-A6
+5V
-A8
BLK _ SD
-A10
BLK _ SCK
-A11
BLK _ LCK
-A12
BLK _ DEN*
-A13
-A9
BLK _ CNDR*
-A14
BLK _PW
-A15
-A7
4–12
COPYRIGHT © 1998 CANON INC.
Blank exposure lamp (LA3)
J551
-10
-8
-6
-5
Control
-4
circuit
-3
-7
-2
-1
-9
Figure 4-112
CANON NP7161/NP7160 REV.0 AUG. 1998 PRINTED IN JAPAN (IMPRIME AU JAPON)
LED circuit
(40 pcs)
Center
(10 pcs)