R -3A54
I?-3E54
TEST PROCEDURES
PROCEDURE
LETTER
COMPONENT TEST
A
MAGNETRON TEST
’ NEVER TOUCH ANY PART IN THE CIRCUIT WITH YOUR HAND OR AN INSULATED
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 LITRE WATER LOAD)
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. 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 formula is as follows;
p=
8330 x AT
t
Our condition for the water load is as follows:
/
Room temperature
. . . . ..*..................... 23 + 2°C Power supply Voltage . . . . . . . . . . . . . Rated voltage /
Water load
. . . ...2000 ml Initial temperature
. . . . ...23&1 “C Heating time . . . . . . . . 2min. 8 sec. j
P=65xAT
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.
D) Place the two beakers as touching each other in the centre of the cavity.
E) Set the timer to 2minute and 8 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 2minute and 8 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.
Example
Initial temperature
Tl = 10°C
T2 =
...............................................................................
11 “C
Temperature after 2min.
8 sec. ..........................................................
Tl =
20°C T2 = 21 “C
Temperature difference Cold-Warm
........................................... AT1 = 10°C
AT2 = 10°C
Mean temperature rise AT ........
AT = (AT1 +AT2) / 2 - (IOOC + IO’C) / 2 = 10°C
Measured output power
The equation is “P= 65 x AT”
...................................................
P= 65 x 10°C = 650 Watts
NOTE: The measured output power should be at least +I5 % of the rated output
power.
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