Sharp R-8R51 - Page 22

TEST PROCEDURES (CONT'D)
PROCEDURE
LETTER
COMPONENT
TEST
G THERMISTOR TEST
!
—_____GARAYOUT
35
CHEEKS-ssp-Disconmect-connectorEtromthe-CPUTInt—MSaSUTETNETESST
.
ance
of
the
thermistor
with
an
ohmmeter.
Connect
the
ohmmeter
leads
to
Pin
No’s
E-3
and
E-4.
a
Room
Temp.
—
oe
|
Resistance
68
F(20'C)
-
86°F(30°C)
—
Approx.
326kQ
-
175k
If
the
meter
does
not
indicate
above
resistance,
replace
the
thermistor.
-
CARRY
OUT
4R
CHECKS
7
P
RELAY
TEST
|
8
:
CARRY OUT 3D CHECKS
Disconnect
the
leads
from
the
primary
of
the
power
transformer.
Make
sure
that
the
leads
remain
isolated
from
other
oven
components
and
chassis.(Use
insulation
tape
if
necessary.)
Reconnect
the
supply.
.
Check
voltage
between
Pin
Nos.
3
and
5
of
the
3-pin
connector
(A)
on
the
control
unit
with
an
A.C.
voltmeter.
The
meter
should
indicate
220-230
volts,
if
not
check
oven
circuit.
Shut-off, Cook and Heater Relay Test
These relays are operated by D.C. voltage.
Check
voltage
at
the
relay
coil
with
a
D.C.
voltmeter
during
the
microwave
cooking
or
convection
cooking operation.
DC. voltage indicated __.......... Defective relay.
DC.
voltage
not
indicated
........
Check
diode
which
is
connected
to
the
relay
coil.
If
diode
is
good, contro! unit is defective.
RELAY
SYMBOL
:
OPERATIONAL
.
CONNECTED
COMPONENTS
i
VOLTAGE
ae
_
Approx. 13 V.D.C. © Qven lamp and Turntable motor
“Approx. 13 V.0.C.: Power transformer
| Approx. 13 V.B.C. . Convection heater ~
|
Approx.
13V.D.C.
|
Grillheater
Approx, 14 V.D.C, ; Damper motor
a Approx. 14 V.D.C. Convection motor * -
Approx. 13V.D.C. | Cooling fanmotor
/, Approx.14V.D.C. Rotisserie motor,
_ Approx.13V.D.C. ° Surge resistor
CARRY OUT 4R CHECKS
QO
TOUCH
CONTROL
PANEL
ASSEMBLY
TEST
The
touch
control
panel
consists
of
circuits
including
semiconductors
such
as
LSt,
ICs,
etc.
Therefore,
unlike
conventional
microwave
ovens,
proper
maintenance
cannot
be
performed
with
only
a
voltmeter
and
ohmmeter.
In
this
service
manual,
the
touch
control
panel
assembly
ts
di-
vided
into
two
units,
Control
Unit
and
Key
Unit
,
troubleshooting
by
unit
replacement
is
de-
scribed
according
to
the
symptoms
indicated.
1. Key Unit.
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.
c)
When
touching
the
pads,
sometimes
a
pad
produces
no
signal.
2. Control Unit
The
following
symptoms
indicate
a
defective
contro!
unit.
Replace
the
control
unit.
2-1 Programming problems.
a)
When
touching
the
pads,
a
certain
group
of
pads
do
not
produce
a
signal.
2-2 Display problems.
a)
For
a
certain
digit,
all
or
some
segments
do
not
light
up.
20