Canon PC740 Service Manual - Page 103

Detecting, Errors, Composite, Power, Supply, Protection, Mechanism, Circuit

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OPERATIONS AND TIMINGMil C. Detecting Errors by the Composite Power Supply PCB The copier's composite power supply PCB is equipped with a microprocessor (Q900) which serves to run a self diagnosis program to check the output from each power supply and its communications with the DC controller PCB. When an error occurs, the microprocessor communicates with the DC controller PCB so that the results of self diagnosis may be indicated in the display on the control panel. 1. Overcurrent (low voltage) If the composite power supply PCB finds an error in a DC load, it will turn off the relay (RL601) to cut off the AC input. 2. Error in the Control Value (high voltage) If the composite power supply PCB finds that the difference between the setting and the actual value of either of the following voltages is not as specified, it will indicate `E064' on the control panel. • primary DC bias • developing DC bias • transfer bias 3. Error in the Control Value (low voltage) If the composite power supply PCB finds that the difference between the setting for +24 V of the DC output and the control value is not as specified, it will indicate 'E803' on the display of the control panel. 4. Error in the Communication with the DC Controller If the DC controller PCB finds an error in the communication between the DC controller PCB and the composite power supply PCB, `E240' will appear in the display of the control panel for about 4 sec; thereafter, the relay (RL601) is turned off to cut off the AC input. D. Protection Mechanism of the Power Supply Circuit The composite power supply PCB has an overcurrent detection function which turns on to stop the output. When the output has stopped, it may be reset by opening the copier's top unit, correcting the load, and turning on the power switch. The built-in fuse (FU102), however, will blow if loads are repeatedly short circuited and reset. COPYRIGHT © 1994 CANON INC. CANON PC72074011501170 REY.0 AUG.1994 PRINTED IN JAPAN (await AU JAPON) 3 - 63

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OPERATIONS
AND
TIMING
Mil
C.
Detecting
Errors
by
the
Composite
Power
Supply
PCB
The
copier's
composite
power
supply
PCB
is
equipped
with
a
microprocessor
(Q900)
which
serves
to
run
a
self
diagnosis
program
to
check
the
output
from
each
power
supply
and
its
communications
with
the
DC
controller
PCB.
When
an
error
occurs,
the
microproces-
sor
communicates
with
the
DC
controller
PCB
so
that
the
results
of
self
diagnosis
may
be
indicated
in
the
display
on
the
control
panel.
1.
Overcurrent
(low
voltage)
If
the
composite
power
supply
PCB
finds
an
error
in
a
DC
load,
it
will
turn
off
the
relay
(RL601)
to
cut
off
the
AC
input.
2.
Error
in
the
Control
Value
(high
volt-
age)
If
the
composite
power
supply
PCB
finds
that
the
difference
between
the
setting
and
the
actual
value
of
either
of
the
following
voltages
is
not
as
specified,
it
will
indicate
`E064'
on
the
control
panel.
•
primary
DC
bias
•
developing
DC
bias
•
transfer
bias
3.
Error
in
the
Control
Value
(low
volt-
age)
If
the
composite
power
supply
PCB
finds
that
the
difference
between
the
setting
for
+24
V
of
the
DC
output
and
the
control
value
is
not
as
specified,
it
will
indicate
'E803'
on
the
display
of
the
control
panel.
4.
Error
in
the
Communication
with
the
DC
Controller
If
the
DC
controller
PCB
finds
an
error
in
the
communication
between
the
DC
con-
troller
PCB
and
the
composite
power
supply
PCB,
`E240'
will
appear
in
the
display
of
the
control
panel
for
about
4
sec;
thereafter,
the
relay
(RL601)
is
turned
off
to
cut
off
the
AC
input.
D.
Protection
Mechanism
of
the
Power
Supply
Circuit
The
composite
power
supply
PCB
has
an
overcurrent
detection
function
which
turns
on
to
stop
the
output.
When
the
output
has
stopped,
it
may
be
reset
by
opening
the
copier's
top
unit,
cor-
recting
the
load,
and
turning
on
the
power
switch.
The
built-in
fuse
(FU102),
however,
will
blow
if
loads
are
repeatedly
short
circuited
and
reset.
COPYRIGHT
©
1994
CANON
INC.
CANON
PC72074011501170
REY.0
AUG.1994
PRINTED
IN
JAPAN
(await
AU
JAPON)
3
-
63