Canon NP6085 Service Manual page 114

3. OPERATIONS AND TIMING
The LINT signal varies the pulse duty between
10% and 90% according to the setting of the Copy
Density key, density of the original used, sensitiv-
ity of the drum, and the setting of the intensity
control VR to execute phase control so that the
supply voltage to the scanning lamp changes
between 45 to 80 V (100V model) or between 98
and 175 V (200V model) in terms of effective val-
ues.
In the case of photo mode, however, a voltage
lower than normal by 5 V is supplied.
Figure 3-307
c. Detecting the Activation of the Scanning
Lamp
The activation detection circuit generates the
ON detection signal=1 at all times whenever the
scanning lamp or the option C.F.F. lamp is ON.
The LAA signal is sent to the error detection cir-
cuit on the DC controller PCB.
If a fault such as a short circuit in the ON circuit
causes the scanning lamp to turn ON despite the
lamp ON signal LRD=0, the LAA signal=1 will be
generated. The error detection circuit on the DC
controller compares the LAA signal and the LRD
signal, and sends the power switch OFF signal
( ) to the power supply circuit to cut off the
PWOFF
AC power supply to the lamp regulator upon detec-
tion of error activation. (For details, see the descrip-
tions on the error detection circuit on p. 3-129.)
The activation detection circuit of the lamp reg-
ulator monitors the activation of the fixing heater
at the same time. (For details, see p. 3-128.)
d. Switching the Lamps
The DC power to the option C.F.F. is supplied
by the lamp regulator.
The scanning lamp is supplied with DC power
when the lamp switching signal (LASEL) from the
DC controller PCB is '1', and the C.F.F. lamp is
supplied with DC power when it is '0'.
This switching mechanism is limited to LRD=0
(lamp OFF) and is automatic when the C.F.F. is in use.
3-56
COPYRIGHT © 1996 CANON INC.
10% pulse duty
90% pulse duty
CANON NP6085 REV.0 JULY 1996 PRINTED IN JAPAN (IMPRIME AU JAPON)
3. Automatic Exposure Control (AE)
The NP6085 is equipped with a mechanism
that automatically controls the intensity of the
scanning lamp according to the density of the
original being used.
In AE mode, fogging-free copies may be
obtained without having to adjust the copy densi-
ty manually to suit the individual originals. In addi-
tion, the lamp intensity controlled by the AE
mechanism is indicated on the copy density indi-
cator on the control panel.
The NP6085's AE mode may be AE mode by
the copier or AE mode by the RDF. The RDF's AE
mode will be used when originals are set in the
RDF.
If the RDF's AE mechanism suffers a fault,
however, the copier's AE mode may be used
(selected in service mode).
The density must be controlled manually in
stream reading mode, since AE is not executed
on the copier.
a. AE Mode in the Copier (CMAAE)
During AE rotation (AER), the scanner is
moved forward by 120 mm while keeping the
scanning lamp ON; when the scanner is moved in
reverse, the surface potential of the four points
shown in Figure 3-308 are measured, and the
results are sent to the DC controller PCB.
The DC controller PCB, in response, com-
putes the average from the measurements of the
surface potential to determine the intensity for the
scanning lamp during copying.
120 mm
4 3 2 1
30 30 30 30 mm
Figure 3-308