Sharp R-771 OE User Manual

TEST PROCEDURES (CONT’D)
PROCEDURE
LETTER
COMPONENT TEST
A
(Cont’d)
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 202 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 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 shoula be around 20°C.
5. Power supply voltage should be 240 volts.
B
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 107 ohms, and the resistance of filament coil should
be less than 1 ohm. With 240 volts A.C. applied to the primary winding, the voltage across the filament winding
should be approximately 3.2 volts A.C. (HIGH VOLTAGES ARE PRESENT TO HIGH VOLTAGE TERMINAL, SO
EXTREME CAUTION SHOULD BE OBSERVED.)
c
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 direc-
tions,, or if an infinite resistance is read in both directions, the rectifier is probably defective and should be replaced
and check short protector.
D
HIGH VOLTAGE CAPACITOR TEST
DISCHARGE THE HIGH VOLTAGE CAPACITOR BEFORE TOUCHING ANY OVEN COMPONENTS OR
WIRING.
If the capacitor is open, no high voltage will be available to the magnetron. Disconnect input leads and check for short
or open between the terminals using an ohmmeter.
Checking with a high ohm scale, if the high voltage capacitor is normal, the meter will indicate continuity for a short
time and should indicate an open circuit once the capacitor is charged. If the above is not the case, check the
capacitor with the ohmmeter to see if it is short circuited between-the terminals. If it is short circuited, replace the
capacitor.
E
SHORT PROTECTOR TEST
DISCHARGE THE HIGH VOLTAGE CAPACITOR BEFORE TOUCHING ANY OVEN COMPONENTS OR WIRING.
Isolate the short protector from the circuit. Using the highest ohm scale of the meter, read the resistance across the
terminals, reverse the leads to the short protector terminal and observe meter reading. If an infinite resistance is
read in both direction, the short protector is good.
If a short is indicated in either direction, the one is probably defective and should be replaced.
14

Sharp R-771 OE Specifications

General

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