Controlling The Scanning Lamp Intensity; Outline; Operations - Canon NP6045 Service Manual

CHAPTER 4 IMAGE FORMATION SYSTEM
B. Controlling the Scanning Lamp Intensity

1. Outline

Figure 4-105 shows the circuit used to control the intensity of the scanning lamp, and
the circuit has the following functions:
Turning ON and OFF the scanning lamp.
Controlling the intensity of the scanning lamp.
• Maintains the intensity to a specific level against changes in the voltage of the
power supply.
• Controls the intensity to suit the sensitivity of the drum.
• Controls the intensity to suit the density of the originals (AE control).
Checks the activation of the scanning lamp.

2. Operations

a. Turning ON and OFF the Scanning Lamp
When LAON (scanning lamp ON signal) is '0', the output of the differential
amplification/potential control circuit goes '0', keeping the arc circuit from turning ON
and, thereby, not supplying power to the scanning lamp (LA1).
When LAON goes '1', the output of the differential amplifier/phase control circuit
goes '1', causing the arc circuit to turn ON and, thereby, supplying power to the scanning
lamp (LA1).
b. Controlling the Intensity of the Scanning Lamp
The intensity of the scanning lamp is increased or decreased by controlling the
supply voltage to the scanning lamp according to the intensity adjustment signal (LINT)
from the DC controller PCB.
12V
Q159
Error
detection
circuit
Q156
D/A
converter
DC controller PCB
4-6
COPYRIGHT © 1997 CANON INC.
PWOFF
J111-
CVRON J503-4
B6
J111-
LINT J503-2
B7
J111-
LAON J503-2
B8
Figure 4-105
Lamp ON
detection
circuit
HIM1
Differential
amplifier
phase control
power voltage
circuit
Arc circuit
Lamp regulator
CANON NP6045 REV. 1 MAR. 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)
Power switch
SW1
J501-3
Thermal
fuse
TP2
Scanning
lamp
J501-1