Sharp R308jsf Service Manual

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TROUBLESHOOTING GUIDE
Never touch any part in the circuit with your hand or an uninsulated too\
l while the power supply is connected.
When troubleshooting the microwave oven, it is helpful to follow the Seq\
uence of Operation in performing the checks. Many
of the possible causes of trouble will require that a specific test be p\
erformed. These tests are given a procedure letter whic h
will be found in the Test Procedure section.
IMPORTANT: If the oven becomes...

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AMAGNETRON ASSEMBLY TEST
Home fuse or circuit breaker blows
when power cord is plugged into wall
receptacle
C/T fuse blows when power cord is
plugged into wall receptacle.
All letters and indicators do not ap-
pear in display when power cord is
first plugged into wall outlet.
Display does not operate properly
when STOP/CLEAR key is touched.
(Buzzer should sound and : or time
of day should appear in display.)
Oven lamp does not light when door
is opened.
Oven lamp does...

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TEST PROCEDURES
PROCEDURE
LETTERCOMPONENT TEST
BPOWER TRANSFORMER TEST
1. Disconnect the power supply cord, and then remove outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
4. Disconnect the primary input terminals and measure the resistance of the transformer with an ohmmeter.
Check for continuity of the coils with an ohmmeter. On the R x 1 scale, the resistance of the primary coil should
be less than 1 ohm and the resistance of the...

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TEST PROCEDURES
PROCEDURE
LETTERCOMPONENT TEST
indicated in both directions, or if an infinite resistance is read in both directions, the rectifier is probably
defective and should be replaced.
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
NOTE: Be sure to use an ohmmeter that will supply a forward bias...

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TEST PROCEDURES
PROCEDURE
LETTERCOMPONENT TEST
switch. The meter should indicate an open circuit with the door open and a closed circuit with the door closed.
If improper operation is indicated, replace the secondary interlock switch.
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
PRIMARY INTERLOCK SYSTEM...

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TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
3. Discharge high voltage capacitor.
4.
If the C/T fuse is blown when the door is opened, check the primary inte\
rlock relay, secondary interlock switch and
monitor switch according to the TEST PROCEDURE for those switches befo\
re replacing the blown C/T fuse.
CAUTION: BEFORE REPLACING A BLOWN C/T FUSE, TEST THE PRIMARY INTERLOCK RELAY,
SECONDARY INTERLOCK SWITCH, DOOR SENSING SWITCH AND MONITOR SWITCH
FOR PROPER...

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3. If the Key unit  or control unit is defective.
1) Disconnect the power supply cord, and then remove outer case.
2) Open the door and block it open.
3) Discharge high voltage capacitor.
4) Replace the control unit assembly.
5) Reconnect all leads removed from components during testing.
6) Re-install the outer case (cabinet).
7) Reconnect the power supply cord after the outer case is installed.
8) Run the oven and check all functions.
4. When testing is completed,
1)...

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DC. voltage indicated ................... Defective relay.
DC. voltage not indicated .............Check diode which is connected to the relay coil. If diode is good,
control unit is defective.
RELAY SYMBOL OPERATIONAL VOLTAGE CONNECTED COMPONENTS
RY1 Approx. -12.0V D.C. Oven lamp / Turntable motor / Cooling fan motor
RY2 Approx. -11.0V D.C. Power transformer
  8. Disconnect the power supply cord, and then remove outer case.
  9. Open the door and block it open.
10....

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TEST PROCEDURES
PROCEDURE
LETTERCOMPONENT TEST
2) Open the door and block it open.
3) Discharge high voltage capacitor.
4) Disconnect the leads to the primary of the power transformer.
5)Ensure that these leads remain isolated from other components and oven chassis by using insulation
tape.
6) After that procedure, re-connect the power supply cord.
7) Follow the troubleshooting guide given below for repair.
STEPS OCCURRENCE CAUSE OR CORRECTION
The rated AC voltage is...

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DESCRIPTION OF LSI
LSI
The I/O signal of the LSI is detailed in the following table.
Pin No. Signal I/O Description
1P50 INSignal coming from touch key.
When either G9 line on key matrix is touched, a corresponding signal out of P22 - P26 and P31
- P33 will be input into P50. When no key is touched, the signal is held at “H” level.
2P51 IN
Signal similar to P50.
When either G10 line on key matrix is touched, a corresponding signal will be input into P51.
3P52 IN
Signal...