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R-9380
TEST
PROCEDURES
PROCEDURE
LETTER
COMPONENT
TEST
A
MAGNETRON
ASSEMBLY
TEST
DISCHARGE
THE HIGH
VOLTAGE
CAPACITOR
BEFORE TOUCHING
ANY
OVEN COMPO-
NENTS OR WIRING.
To test for an open filament,
isolate the magnetron
from the high voltage
circuit.
A continuity
check across the magnetron
filament
leads should
indicate
less than 1 ohm.
To test for a shorted
magnetron,
connect
the ohmmeter
leads between
the magnetron
filament
leads and chassis ground.
This test should
indicate
an infinite
resistance.
If there is little or no
resistance,
the magnetron
is grounded
and must be replaced.
Power output
of the magnetron
can be measured
by performing
a water temperature
rise test.
This test should
only be used if above rests do not indicate
a faulty
magnetron
and there is no
defect in the following
components
or wiring:
rectifier,
high voltage
capacitor,
heater transformer
and power transformer.
MICROWAVE
OUTPUT
POWER
Microwave
output
power from the magnetron
can be measured
by way of substitution,
i.e. it can
be measured by using 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;
Pxt/4.2=;Vx
LIT
P (W) = 4.2 x V x AT I t
Our condition
for the water load is as follows:
Water load . . 2000 ml,
Heating
time . ..I 20 seconds
P-70x
AT
Measuring
method;
1. Put the water load of two
(2) litres on the center of the oven shelf.
The water load should
be arranged
in two (2) Pyrex beakers, the size of which
is one (1) litre, and be placed at right
and left, side by side, on the oven shelf.
2. Measure the temperature
of water before heating
and also after heating
during
120 seconds
by microwave,
and calculate
the temperature
rise. The temperature
rise should
be the average
of temperature
differences
measured
in each beaker.
3. The output
power should
be calculated
as follows.
In case the measuring
result is not satis-
factory,
execute the measurement
several times and judge the result from the synthetic
point
of view.
Microwave
output
power should
be within
+ 15% of the nominal
one.
Calculation
of output
power;
Microwave
output
po\iver . . . P (W) = 70 x AT ( "C)
AT = ( ATL
+
ATR)
/ 2 : average temperature
rise
ATL = (TL2 - TLI),
ATR = (TR2 - TRl)
TL2 : water temperature
after heating
in left beaker
TLI
: water temperature
before heating
in left beaker
TR2 : water temperature
after heating
in right beaker
TRI
: water temperature
before heating
in right beaker
Measuring
condition;
As the microwave
output
is affected
by several conditions,
the measurement
should
be made
carefully
with following
attentions.
1. Initial
temperature
of salt water should
be 20
+ 1 "C.
(The salt water should
be contained
bon (1) percent
of salt.)
Well and quickly
stir the water and the temperature
measurement
should
be done immediately
after heating.
2. The graduation
of thermometer
should
be scaled by 0.1 "C at minimum
and an accurate
mer-
cury thermometer
is recommended.
IO
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