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OPERATIONS AND
TIMING
I
C.
Controlling the
Scanning
Lamp
1.
Outline
The
scanning
lamp
(LA1)
is
controlled
by
the
DC
controller
PCB;
see
Figure
3-18.
Specifically,
the
DC
controller
•
turns the
scanning lamp
ON
and
OFF.
•
controls the
intensity of
the
scanning
lamp.
2.
Mechanism
a.
Turning the
Scanning
Lamp
ON
and
OFF
The
microprocessor (Q303)
on
the
DC
controller
PCB
controls
the
lamp
regula-
tor.
The
scanning lamp goes
ON
when
the
scanning
LAMP
ON
command
(LAON)
is '1',
and
it
goes
OFF
when
the
signal
is
'0'.
b.
Controlling the
Intensity of
the
Scanning
Lamp
The
intensity of
the
scanning lamp
is
switched
between
when
the black devel-
oping
assembly
is
used
and
when
the
CT
unit
is
used.
When
the
CT
unit
is
used, the
LIGHT
INTENSITY
CONTROL
command
(LIC)
goes
'0'
to raise
the
lamp
voltage by
about
3.5
V
higher than
when
the black
developing
assembly
is
used.
During
AE
exposure,
however,
the
voltage (70 V) applied
to
the
scanning
lamp remains
the
same.
The NP-1550
adjusts the
copy
density
using
its
development
bias;
see
p.
3-22.
Error Protection
The>
condition of the
scanning lamp
is
monitored
using the
LIGHT
signal
(LGHT).
If
the
LIGHT
signal
(LIGHT)
is
received
by the
DC
controller
for
about
20
sec,
the
error detection
circ
uit
gene
rates the
AC
SHUTOFF
signal
(ACOFF)
to
force
the
relay
(S105)
on
the
AC
driver/DC
power
supply,
PCB
to
go OFF,
thereby
cutting
AC
power
supply
(P.
3-39).
In
this
case
E220
error
is
displayed.
DC
controller
PCB
Lamp
regulator
Figure 3-18
3-20
COPYRIGHT©
1992
CANON
INC.
CANON
NP-1550
REV.1
SEPT. 1992
PRINTED
IN
JAPAN
(IMPRIKE
AU JAP0N)
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