Sharp R21lcf Service Manual

R21LCF
6 – 3
3) If the door is opened, and the primary interlock relay (RY1) andsecondary interlock switch contacts fail to open, the monitor fuse
blows simultaneously with closing  of the monitor switch contacts.
CAUTION: BEFORE REPLACING  A BLOWN MONITOR FUSE TEST
THE DOOR SENSING SWITCH, PRIMARY INTERLOCK
RELAY (RY1), SECONDARY INTERLOCK SWITCH AND
MONITOR SWITCH FOR PROPER OPERATION. (REFER
TO CHAPTER TEST PROC
NOTE: MONITOR FUSE AND MONITOR SWITCH ARE REPLACED
AS AN ASSEMBLY.
4. ANTENNA MOTOR
The...

R21LCF
7 – 1
R21LCFService Manual CHAPTER 7. TROUBLESHOOTING GUIDE 
When troubleshooting the microwave oven, it is helpful to follow the Sequence of Operation in performing the checks. Many of th e possible causes of
trouble will require that a specific test  be performed. These tests are given a proc edure letter which will be found in the Test Procedure section.
IMPORTANT:
If the oven becomes inoperative because of a blown monitor fuse,
check the monitor switch, primary in terlock relay (RY1), door...

R21LCF
8 – 1
R21LCFService Manual CHAPTER 8. TEST PROCEDURES
[1] Procedure A: MAGNETRON ASSEMBLY 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. 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.
5. To test for a shorted magnetron, connect the ohmmeter leads bet ween the magnetron filament...

R21LCF
8 – 2
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 voltage of more than 6.3 volts.
[4] Procedure D: HIGH  VOLTAGE CAPACITOR 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. If the capacitor is open, no high voltage will be available to...

R21LCF
8 – 3
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
[7] Procedure F: PRIMARY INTERLOCK SYSTEM TEST
1. DOOR SENSING SWITCH
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. Isolate the switch and connect the ohmmeter to the common (COM.) and normally open (NO) terminal of the switch. The meter sho uld indicate an
open circuit with the door open...

R21LCF
8 – 4
3. Discharge high voltage capacitor.
4. If the monitor fuse is blown when the door is opened, check the primary interlock relay, secondary interlock switch and monitor switch according to
the TEST PROCEDURE for those switches  before replacing the blown monitor fuse.
CAUTION: BEFORE REPLACING A BLOWN MONITO R FUSE, TEST THE PRIMARY INTERLOCK RELAY, SECONDARY INTERLOCK SWITCH,
DOOR SENSING SWITCH AND MONITOR SWITCH FOR PROPER OPERATION.
If the monitor fuse is blown by improper switch...

R21LCF
8 – 5
When testing is completed,
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) Reconnect all leads removed from components during testing.
5) Re-install the outer case (cabinet).
6) Reconnect the power supply cord after the outer case is installed.
7) Run the oven and check all functions.
[12] Procedure L: RELAY TEST
1. Disconnect the power supply cord, and then remove outer case.
2. Open the door and...

R21LCF
8 – 6
2. Follow the troubleshooting guide given below, if indicator does not light up after above check and repairs are finished.
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 leads to the primary of the power transformer.
5) Ensure that these leads remain isolated from ot her components and oven chassis by using insulation tape.
6) After that procedure, re-connect the power supply cord....

R21LCF
9 – 1
R21LCFService Manual CHAPTER 9. TOUCH CONTROL PANEL ASSEMBLY
[1] OUTLINE OF TOUCH CONTROL PANEL 
1. Control Unit 
Control unit consists of LSI, power source circuit, synchronizing signal
circuit, reset circuit, buz zer circuit, encoder circui t and indicator circuit.
1) LSI
This LSI controls the encoder si gnal, relay driving signal for oven
function, buzzer signal and LED signal.
2) Power Source Circuit This circuit generates voltage necessary in the control unit. 
Symbol Voltage...

R21LCF
9 – 2
Connect an external power source to the power input terminal of
the touch control panel, then it is possible to check and repair the
controls of the touch control panel;  it is also possible to check the
sensor-related controls of the t ouch control panel by using the
dummy resistor(s).
3. Servicing Tools
Tools required to service the  touch control panel assembly.
1) Soldering iron: 60W
(It is recommended to use a soldering iron with a grounding termi-
nal.)
2) Oscilloscope: Single beam,...