Operation - Canon NP7160 Service Manual

CHAPTER 4 IMAGE FORMATION SYSTEM

2. Operation

a. Turning On/Off the Scanning Lamp
When the scanning lamp drive signal (LMPDR) is '0', the output of the control circuit goes
'0', keeping the drive circuit from turning on and therefore not supplying the scanning lamp
(LA1) with AC power.
When LMPDR is '1', the output of the control circuit will be '1', turning on the drive circuit
and thereby supplying the scanning lamp (LA1) with AC power.
b. Controlling the Intensity of the Scanning Lamp
The intensity of the scanning lamp is increased/decreased by controlling the voltage of the
power supplied to the scanning lamp according to the level of the pulse width modulation signal
(LMP_PWM) from the DC controller PCB.
LMP_PWM varies the pulse duty between 10% and 90% to suit the selected reproduction
ratio so as to control the voltage of the power supplied to the scanning lamp as shown in Table 4-
101 (actual value).
c. Detecting the Activation of the Scanning Lamp
The control circuit on the lamp regulator PCB generates the drive detection signal
(LMPDT) at all times while the scanning lamp remains on, and sends the signal to the lamp
activation detection IC (IC113) on the DC controller PCB.
If the scanning lamp remains on for 21 sec or more, the error detection circuit will cause the
AC_24V_ON signal to go '0', thereby cutting the supply of AC power to the lamp regulator
PCB.
If an error is identified in the scanning lamp, the DC controller PCB will cut the AC power
to the lamp regulator and, at the same time, will indicate 'E220' on the control panel.
4–4
COPYRIGHT © 1998 CANON INC.
t
T
Figure 4-104
Power supply Pulse duty
120V 10 to 90%
230V 10 to 90%
Table 4-101
CANON NP7161/NP7160 REV.0 AUG. 1998 PRINTED IN JAPAN (IMPRIME AU JAPON)
Pulse duty (%) = t / T x 100
DC output
45 to 80V
98 to 175V