Sharp R-771 OE User Manual

TEST PROCEDURES
PROCEDUR-E ’
LETTER
COMPONENT TEST
A
MAGNETRON ASSEMBLY TEST
DISCHARGE THE HIGH VOLTAGE CAPACITOR BEFORE TOUCHING ANY OVEN COMPONENTS 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 tests do not indicate a faulty magnetron and there is no defect in the following components
or wiring:
rectifier, high voltage capacitor 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.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. AT.
The formular is as follows;
P.t
4.2
= V.AT
P=
4.2 . V.AT
t
ov
Our condition for the water load is as follows;
Water load . . . .2000 ml
Heating time. . .
120 seconds (2 minutes)
pi-q
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 two minutes 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 satisfactory, 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 power. . . P (W) = 70 x nT (“C)
s =--
(ATL + ATR)
2
: average temperature rise
ATL = (TL~ - TL,)
ATR = (TR, - TR,)
Q-2
: water temperature after heating in left beaker
TI-1
: water temperature before heating in left beaker
TR2
TR,
: water temperature after heating in right beaker
: water temperature before heating in right beaker
13

Sharp R-771 OE Specifications

General

Brand	Sharp
Model	R-771 OE
Category	Microwave Oven
Language	English