Sharp R-771(W)N - Page 18

TEST
PROCEDURES
(CONT'D)
PROCEDURE
LETTER
COMPONENT
TEST
K
GRILL
HEATING
ELEMENT
(TOP)
AND
BOTTOM
HEATING
ELEMENT
TEST
:
&
CARRY
OUT
3D
CHECKS.
Before
carrying
out
the
following
tests
make
sure
the
heating
element
is
cool
completely.
®
1.
Resistance
of
heating
element.
Disconnect
the
wire
leads
to
the
heating
element
to
be
tested.
Using
ohmmeter
with
low
resistance
range.
Check
the
resistance
across
the
terminals
of
the
heating
element
as
described
in
the
following
table.
Table:
Resistance
of
heating
element
Paris
name
Resistance
Bottom
heating
element
Approximately
66
&
2.
Insulation
resistance.
Disconnect
the
wire
leads
to
the
heating
element
to
be
tested.
Check
the
insulation
resistance
between
the
element
terminal
and
cavity
using
a
500V
-
400MQ
insulation
tester.
The
insulation
resistance
should
be
more
than
10
MQ
in
the
cold
start.
if
the
results
of
above
test
1
and/or
2
are
out
of
above
specifications,
the
heating
elementis
probably
faulty
and
should
be
replaced.
e
CARRY
OUT
4R
CHECKS.
|
L.
TOUCH
CONTROL
PANEL
ASSEMBLY
TES
The
touch
control
panel
consists
of
circuits
including
semiconductors
such
as
LSI,
ICs,
etc.
Therefore,
unlike
conventional
microwave
ovens,
proper
maintenance
can
not
be
performed
with
only
a
voltmeter
and
ohmmeter.
Inthis
service
manual,
the
touch
control
panel
assembly
is
divided
into
two
units,
Control
Unit
and
Key
Unit,
and
troubleshooting
by
replacement
is
described
according
to
the
symptoms
indicated.
a
1.
Key
Unit
Note:
Check
key
unit
ribbon
connection
before
replacement.
@
The
following
symptoms
indicate
a
defective
key
unit.
Replace
the
key
unit.
a)
When
touching
the
pads,
a
certain
pad
produces
no
signal
at
all.
b)
When
touching
a
number
pad,
two
figures
or
more
are
displayed.
ce)
When
touching
the
pads,
sometimes
a
pad
produces
no
signal.
2,
Control
Panel
The
following
symptoms
indicate
a
defective
contro!
unit.
Before
replacing
the
conirol
unit.
perform
the
key
unit
test
(Procedure
N)
to
determine
if
control
unit
is
faulty.
2-1
\Inconnection
with
pads
a)
When
touching
the
pads,
a
certain
group
of
pads
do
not
produce
a
signal.
b)
When
touching
the
pads,
no
pads
produce
a
signal.
Se
2.2
\n
connection
with
indicators
a)
Ata
certain
digit,
all
or
some
segments
do
not
light
up.
b)
At
a
certain
digit,
brightness
is
low.
c)
Only
one
indicator
does
not
light
up.
d)
The
corresponding
segments
of
all
digits
do
not
light
up;
or
they
continue
to
light
up.
e)
Wrong
figure
appears.
f)
Acertain
group
of
indicators
do
not
light
up.
.
g)
The
figure
of
all
digits
flicker.
2-3
Other
possible
troubles
caused
by
defective
contro}
unit.
a)
Buzzer
does
not
sound
or
continues
to
sound.
|
b)
Clock
does
not
operate
properly.
c)
Cooking
is
not
possible.
a
NM
KEY
UNIT
TEST
if
the
display
fails
to
clear
when
the
STOP
pad
is
depressed,
first
verify
the
flat
ribbon
cable
is
@
marking
good
contact,
verity
that
the
door
sensing
switch
(siop
switch)
operates
properly;
that
is
ihe
contacts
are
closed
when
the
door
is
closed
and
open
when
the
door
is
open.
If
the
door
:
sensing
switch
(stop
switch)
is
good,
disconnecct
the
flat
ribbon
cable
that
connecis
the
key
unit
©
to
the
control
unit
and
make
sure
the
door
sensing
switch
is
closed
(either
close
the
door
or
short
the
door
sensing
switch
connecter).
Use
the
Key
unit
matrix
indicated
on
the
contro!
panel
schematic
and
place
a
jumper
wire
between
the
pins
that
correspond
to
the
STOP
pad
marking
R-771
-
18