Sharp R-9320 Service Manual page 34

TEST PROCEDURES (CONT'D)
PROCEDURE
LETTER
A
(Cont'd)
B
C
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COMPONENT TEST
Calculation of output power;
Microwave output power . . .P (W) = 70 x m ("C)
aT = (ATL + ATR)
2
: average temperature rise
ATL = (TL2 - TL, )
ATR = (TR2 - TR1 )
TL2
: water temperature after heating in left beaker
J-L1
: 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 2OAl'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 O.l'C at minimum and an accurate mercury
thermometer is recommended.
3. Water container should be one (1) litre beaker made of Pyrex glass and its diameter approximately
12 cm.
4. Room temperature should be around 2O'C.
5. Power supply voltage should be 240 volts.
POWER TRANSFORMER TEST
DISCHARGE THE HIGH VOLTAGE CAPACITOR BEFORE TOUCHING ANY
OVEN COMPONENTS OR WIRING.
Disconnect primary input terminals and measure the resistance with an ohmmeter. Check for the
continuity of coils with an ohmmeter. On the RX1 scale, the resistance of the primary coil should be
approximately 1.5 ohms and the resistance of high voltage coil should be approximately 80 ohms,
and the resistance of filament coil should be less than 1 ohm.
(HIGH VOLTAGES ARE PRESENT TO HIGH VOLTAGE TERMINAL, SO
THAT DO NOT INTEND TO MEASURE THE FILAMENT AND HIGH VOLTAGE,)
RECTIFIER TEST
DISCHARGE THE HIGH VOLTAGE CAPACITOR BEFORE TOUCHING ANY
OVEN COMPONENTS OR WIRING.
Isolate the rectifier from the circuit. Using the highest ohm scale of the meter, read the resistance ,
across the terminals and observe, reverse the leads to the rectifier terminals and observe meter /
reading. If a short is indicated in both directions, or if an infinite resistance is read in both directions,
the rectifier is probably defective and should be replaced.
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