Canon PC720 Service Manual - Page 101

Power, Supply, Circuit

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OPERATIONS AND TIMINGIIIIIIII B. Power Supply Circuit The copier's power supply assembly consists of its DC power supply, scanning lamp power supply, and composite power supply circuit, and uses a single main transfer (T101) to supply high voltage. The copier's power supply is equipped with a microprocessor for exchange of data with the DC controller PCB. The copier's power switch is a soft switch, and the copier is equipped with an auxiliary power supply to drive the soft switch. The auxiliary power supply provides the microprocessor (Q900) with +5V power while the power plug is connected and the door switch (DS1) is on. AC power is supplied to the DC power supply assembly when the door switch (DS1) and the power switch on the control panel are turned on. The DC power supply generates +5 V, +24 VR, and +24 VU for the DC controller PCB. When the power switch is turned off, power to the DC controller PCB is cut; to back up data on error codes (E000, E001, E002, E003), the copier uses the capacitor (C123) located within the DC controller circuit. When any of these codes (E000, E001, E002, E003) occurs, charges are stored in the capacitor (C123). The copier indicates `E0' on the control panel if charges exist in the capacitor when the power switch is turned on to indicate that an error associated with the fixing heater is present. Caution: The back-up capacitor (C123) keeps charges for about 5 min after the power switch is turned off. Reference: The tolerances allowed for the DC voltage are as follows: • +5 V ±5% • +24 VR ±5% • +24 VU ±12.5% However, the above values apply on the condition that the AC input tolerances are between -15% and +10°/0. COPYRIGHT © 1994 CANON INC. CANON PC720/14017501770 REVD AUG. 1994 PRINTED IN JAPAN ompRat AU JAPON) 3 - 61

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OPERATIONS
AND
TIMING
IIIIIIII
B.
Power
Supply
Circuit
The
copier's
power
supply
assembly
consists
of
its
DC
power
supply,
scanning
lamp
power
supply,
and
composite
power
supply
circuit,
and
uses
a
single
main
trans-
fer
(T101)
to
supply
high
voltage.
The
copier's
power
supply
is
equipped
with
a
microprocessor
for
exchange
of
data
with
the
DC
controller PCB.
The
copier's
power
switch
is
a
soft
switch,
and
the
copier
is
equipped
with
an
auxiliary
power
supply
to
drive
the
soft
switch.
The
auxiliary
power
supply
provides
the
microprocessor
(Q900)
with
+5V
power
while
the
power
plug
is
connected
and
the
door
switch
(DS1)
is
on.
AC
power
is
supplied
to
the
DC
power
supply
assembly
when
the
door
switch
(DS1)
and
the
power
switch
on
the
control
panel
are
turned
on.
The
DC
power
supply
generates
+5
V,
+24
VR,
and
+24
VU
for
the
DC
controller
PCB.
When
the
power
switch
is
turned
off,
power
to
the
DC
controller
PCB
is
cut;
to
back
up
data
on
error
codes
(E000,
E001,
E002,
E003),
the
copier
uses
the
capacitor
(C123)
located
within
the
DC
controller
cir-
cuit.
When
any
of
these
codes
(E000,
E001,
E002,
E003)
occurs,
charges
are
stored
in
the
capacitor
(C123).
The
copier
indicates
`E0'
on
the
control
panel
if
charges
exist
in
the
capacitor
when
the
power
switch is
turned
on
to
indicate
that
an
error
associated
with
the
fixing
heater
is
present.
Caution:
The
back-up
capacitor
(C123)
keeps
charges
for
about
5
min
after
the
power
switch
is
turned
off.
Reference:
The
tolerances
allowed
for
the
DC
volt-
age
are
as
follows:
•
+5
V
±5%
•
+24
VR
±5%
•
+24
VU
±12.5%
However,
the
above
values
apply
on
the
condition
that
the
AC
input
tolerances
are
between
-15%
and
+10°/0.
COPYRIGHT
©
1994
CANON
INC.
CANON
PC720/14017501770
REVD
AUG.
1994
PRINTED
IN
JAPAN
ompRat
AU
JAPON)
3
-
61