Sharp R-771(W)N - Component Test

TEST
PROCEDURES
(CONT'D)
PROCEDURE
LETTER
COMPONENT
TEST
Initial
temperature
Temperature
after
(47
+
Temperature
difference
Cold-Warm
Measured
output
power
The
equation
is
“P
=
90
x
AT”
JUDGMENT:
The
measured
output
power
should
be
at
least
=
15
%
of
the
rated
output
power.
-
CAUTION:
1°C
CORRESPONDS
TO
90
WATTS.
REPEAT
MEASUREMENT
IF
THE
POWER
!S
INSUFFICIENT.
Heat
up
for
50
sec
B
HIGH
VOLTAGE
TRANSFORMER
TEST
WARNING:
High
voltage
and
large
currents
are
present
at
the
secondary
winding
and
filament
winding
of
the
high
voltage
transformer.
Itis
very
dangerous
to
work
near
this
part
when
the
oven
is
on.
NEVER
make
any
voltage
measurements
of
the
high-voltage
circuits,
including
the
magnetron
filament.
CARRY
OUT
8D
CHECKS.
Disconnect
the
leads
to
the
primary
winding
of
the
high
voltage
transformer.
Disconnect
the
filament
and
secondary
winding
connections
from
the
rest
of
the
HV
circuitry.
Using
an
ohmmeter,
set
ona
low
range,
it
is
possible
to
check
the
continuity
of
all
three
winding.
The
following
readings
should
be
obtained:-
a,
Primary
WINING
.....ccsseeeeeeeseneeseeseesees
approximately
1.9
2
b,
Secondary
WINING
.......seeeseeertesenrees
approximately
96
c.
Filament
Winding
..........ecssseeseeseeeneeeeneenenertees
less
than
71
2
if
the
readings
obtained
are
not
stated
as
above,
then
the
high
voltage
transformer
is
probably
faulty
and
should
be
replaced.
CARRY
OUT
4R
CHECKS.
nena
Cc
HIGH
VOLTAGE
RECTIFIER
ASSEMBLY
TEST
HIGH
VOLTAGE
RECTIFIER
TEST
CARRY
OUT
3D
CHECKS.
isolate
the
high
voltage
rectifier
assembly
from
the
HV
circuit.
The
high
voltage
rectifier
can
be
tested
using
an
ohmmeiter
set
to
its
highest
range.
Connect
the
ohmmeter
across
the
terminal
B+C
of
the
high
voltage
rectifier
and
note
the
reading
obtained.
Reverse
the
meter
leads
and
note
this
second
reading.
The
normal
resistance
is
infinite
in
one
direction
and
more
than
100
kQ
in
the
other
direction.
CARRY
OUT
4R
CHECKS.
5
ASYMMETRIC
RECTIFIER
TEST
ASYMMETRIC
/
RECTIFIER
CARRY
OUT
3D
CHECKS.
C/
HIGH
VOLTAGE
RECTIFIER
Isolate
the
high
voltage
rectifier
assembly
from
the
HV
circuit.
The
asymmetric
can
be
tested
using
an
ohmmeter
set
to
its
highest
range
across
the
terminals
A+B
of
the
asymmetric
rectifier
and
note
the
reading
obtained.
Reverse
the
meter
leads
and
note
this
second
reading.
If
an
open
circuit
is
indicated
in
both
direction
then
the
asymmetric
rectifier
is
good.
If
an
asymmetric
rectifier
is
shorted
in
either
direction,
then
the
asymmetric
rectifier
is
probably
faulty
and
must
be
replaced
with
high
voltage
rectifier.
When
the
asymmetric
rectifier
is
defective,
check
whether
magnetron,
high
voltage
rectifier,
high
voltage
wire
or
filament
winding
of
the
high
voltage
transformer
is
shorted.
R-771 - 15