Sharp Carousel R-7A54 Manual de serviço - Página 6
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R-7A54
TEST PROCEDURES
PROCEDURE
LETTER
COMPONENT
TEST
A
MAGNETRON
TEST
I NEVER TOUCH
ANY
PART
IN THE CIRCUIT
WITH
YOUR
HAND
OR AN INSULATED
I
i TOOL
WHILE
THE OVEN
IS IN OPERATION.
,
/
CARRY
OUT 3D CHECKS
Isolate
the magnetron
from the high voltage
circuit
by removing
all leads connected
to the filament
terminal.
To test
for an open
circuit
filament
use an ohmmeter
to make
a continuity
test
between
the
magnetron
filament
terminals,
the meter
should
show
a reading
of less than
1 ohm.
To test for a short
circuit
filament
to anode
condition,
connect
ohmmeter
between
one of the fil-
ament
terminals
and the case of the magnetron
(ground).
This test should
be indicated
an infinite
resistance.
If a low
or zero resistance
reading
is obtained
then the magnetron
should
be re laced.
(R g 82AOl
U)
MICROWAVE
OUTPUT
POWER
(2 liter
water
load)
The foilowing
test procedure
should
be carried
out with
the microwave
oven
in a fully
assembled
condition
(with
outer
case fitted).
Microwave
output
power
from the magnetron
can be measured
by way of substitution,
i.e. it can be measured
by using
a water
load how
much
it can be absorbed
by the water
load.
To measure
the microwave
output
power
in the microwave
oven,
the relation
of calorie
and watt
is used.
When
P(W)
heating
works
for t(second),
approximately
P x t/4.2
calorie
is generated.
On the
other
hand,
if the temperature
of the
water
with
V(ml)
rises
AT
("C)
during
this microwave
heating
period,
the calorie
of the water
is V x AT.
The formular
is as follows;
P x t / 4.2 = V x AT
P (W)
= 4.2 x V x
AT / t
Our condition
for the water
load
is as follows:
Power supply Voltage ..I........................................~....................................................................,.*.*.....
240 volts /
Water load . . . . . . . 2000
ml
Initial temperature . . . . . . . 23 f /"C
min. 52 sec.
P=75xnT
Heating time . . . . . . . 1
/
I
Measuring method:
A) Use two 1 litre Pyrex beakers with a diameter of approximately of 12cms.
B) Place 1 litre of tap water in each beaker.
C) Mark Tl on the one beaker and mark T2 on the other one. And stir the water and measure the
temperature of water the thermometer and note them. The graduation of the thermometer must
be scaled by 0.1 "C at minimum and an accurate mercury thermometer is recommended.
D) Place the two beakers as touching each other in the centre of the cavity.
E) Set the timer to 1 minute 52 seconds at 100% power (the time required to raise the water
temperature 10 degrees C.)
F) When the oven stops, remove the two beakers from the oven and quickly measure the
temperature of the water by stiring the water with the thermometer and noting the readings.
Example
I
I
I
Initial
temperature
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Temperature
after
1 min.
52 set
Tl
= 23°C
T2 = 24°C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tl
= 33°C
T2 =
Temperature
difference
Cold-Warm
34°C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
=
=
Mean
temperature
rise
AT
AT1
10°C
AT2
10°C
. . . . . . . .
Measured
output
power
AT
= (AT1
+AT2)
/ 2 = (IOOC +
1OT)
/ 2 =
10°C
The equation
is "P=
75 x
AT"
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . P= 75 x 10°C
= 750
Watts
NOTE:
The
measured
output
power
should
be at least
&I5
% of the
rated
output
power.
CAUTION:
1°C CORRESPONDS
TO 75 WATTS.
REPEAT
MEASUREMENT
IF THE POWER
IS INSUFFICIENT.
5