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R -4A52
R-4E52
TEST PROCEDURES
PROCEDURE
LETTER
COMPONENT
TEST
MAGNETRON
TEST
-----.
-
-
j NEVER TOUCH ANY PART IN THE CIRCUIT
WITH YOUR HAND
OR AN INSULATED
I
1 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 inifinite
resistance.
If a low or zero resistance
reading
is obtained
then the magnetron
should
be replaced.
MICROWAVE
OUTPUT
POWER
The following
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.
1 The formulae
is as follows;
I
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:
Room temperature
. . . around
2O"C, Power supply Voltage
. . . 240 volts.
Water load . . . 2000 ml, Initial temperature
. . . 1 O&l OC, Heating time . ..I min. 52 sec.
P = 75 x AT
Measuring
method:
A) Use two 1 litre Pyrex beakers with a diameter of approximately
of 12cms.
B) Place 1 litre of 10°C 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.
Example: The initial
temperature
Tl
= 1 O'C, T2 = 11 "C
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) The time must be measured with stopwatch
or wristwatch.
G) After 1 minute and 52 seconds, stop the oven by opening
the door.
H) Remove the two beakers from the oven and measure the temperature
of the water by stiring the
water with the thermometer
and noting
the readings.
10
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