Sharp R-27STM User manual

R-27STM
1
CONTENTS
BEFORESERVICING-------------------------------------------------------------------2
WARNING TO SERVICE PERSONNEL-------------------------------------------------------3
PRODUCTSPECIFICATIONS -------------------------------------------------------------4
APPEARANCE VIEW--------------------------------------------------------------------4
OPERATIONSEQUENCE----------------------------------------------------------------5
FUNCTIONOFIMPORTANTCOMPONENTS--------------------------------------------------6
TROUBLESHOOTINGGUIDE-------------------------------------------------------------7
TESTPROCEDURES-------------------------------------------------------------------8
TOUCH CONTROL PANELASSEMBLY -----------------------------------------------------12
PRECAUTIONSFORUSINGLEAD-FREESOLDER--------------------------------------------13
COMPONENT REPLACEMENTAND ADJUSTMENT PROCEDURE - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -14
MICROWAVEMEASUREMENT-----------------------------------------------------------19
CIRCUIT DIAGRAMS-------------------------------------------------------------------20
PARTSLIST-------------------------------------------------------------------------24
SERVICE MANUAL
No. S0801R27STPKS
MICROWAVE OVEN
MODEL R-27STM
In interests of user-safety the oven should be restored to its original condition and only parts identical to those specied
should be used.
This document has been published to be used for after sales service only.
The contents are subject to change without notice.
PCSKGTURNSTIR
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BEFORE SERVICING
GENERAL IMPORTANT INFORMATION
This Manual has been prepared to provide Sharp Corp. Service engineers with Operation and Service Information.
It is recommended that service engineers carefully study the entire text of this manual, so they will be qualied to render satisfactory
customer service.
WARNING: THIS APPLIANCE MUST BE EARTHED
IMPORTANT
THE WIRES IN THIS MAINS LEADARE COLOURED IN ACCORDANCE WITH THE FOLLOWING CODE:
GREEN-AND-YELLOW------------------------------- EARTH
BLUE -------------------------------------------------- NEUTRAL
BROWN-------------------------------------------------------LIVE
CAUTION MICROWAVE RADIATION
DO NOT BECOME EXPOSED TO RADIATION FROM THE MICROWAVE GENERATOR OR OTHER PARTS CON-
DUCTING MICROWAVE ENERGY.
Service engineers should not be exposed to the microwave energy which may radiate from the magnetron or other
microwave generating devices if it is improperly used or connected. All input and output microwave connections,
waveguides, anges and gaskets must be secured. Never operate the device without a microwave energy absorbing
load attached. Never look into an open waveguide or antenna while the device is energized.
WARNING
Never operate the oven until the following points are ensured.
(A) The door is tightly closed.
(B) The door brackets and hinges are not defective.
(C) The door packing is not damaged.
(D) The door is not deformed or warped.
(E) There is not any other visible damage with the oven.
Servicing and repair work must be carried out only by trained service engineers.
All the parts marked "∆" on parts list are used at voltage more than 250V.
Removal of the outer wrap gives access to potential above 250V.
All the parts marked "*" on parts list may cause undue microwave exposure, by themselves, or when they are damaged,
loosened or removed.
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WARNING TO SERVICE PERSONNEL
Microwave ovens contain circuitry capable of producing very high voltage and current, contact with any part of the high voltage circuit
will result in electrocution. High voltage capacitor, Power transformer, Magnetron, High voltage rectier assembly, High voltage fuse,
High voltage harness.
REMEMBER TO CHECK 3D
Disconnect the supply.
Door opened, and wedged open.
Discharge the high voltage capacitor.
WARNING: AGAINST THE CHARGE OF THE HIGH-VOLT-
AGE CAPACITOR
The high-voltage capacitor remains charged about 60
seconds after the oven has been switched off. Wait for
60 seconds and then short-circuit the connection of the
high-voltage capacitor (that is, of the connecting lead of
the high-voltage rectifier) against the chassis with the
use of an insulated screwdriver.
Sharp recommend that wherever possible fault-nding is car-
ried out with the supply disconnected. It may, in some cases,
be necessary to connect the supply after the outer case has
been removed, in this event carry out 3D checks and then
disconnect the leads to the primary of the power transformer.
Ensure that these leads remain isolated from other compo-
nents and the oven chassis. (Use insulation tape if neces-
sary.) When the testing is completed, carry out 3D checks and
reconnect the leads to the primary of the power transformer.
REMEMBER TO CHECK 4R
Reconnect all leads removed from components during testing.
Replace the outer case (cabinet).
Reconnect the supply.
Run the oven. Check all functions.
Microwave ovens should not be run empty. To test for the
presence of microwave energy within a cavity, place a cup of
cold water on the oven turntable, close the door and set the
power level to HIGH (100%). And set the microwave timer for
two (2) minutes. When the two minutes has elapsed (timer at
zero) carefully check that the water is now hot. If the water re-
mains cold, carry out 3D checks and re-examine the connec-
tions to the component being tested.
When all service work is completed and the oven is fully assembled, the microwave power output should be checked and microwave
leakage test should be carried out.
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NOTE: Internal capacity is calculated by measuring maximum width, depth
and height. Actual capacity for holding food is less.
15
14
11
1213
62
19
10
7
3
4
8
5
4
PRODUCT SPECIFICATIONS
ITEM DESCRIPTION
Power Requirements 230 - 240 Volts 50 Hertz
Single phase, 3 wire earthed
Power Consumption 1.22 kW
Power Output 800 watts nominal of RF microwave energy (IEC60705 Test Procedure)
Operating frequency 2450 MHz
Outside Dimensions Width 460 mm Height 275 mm including foot
Depth 370 mm
Cooking Cavity Dimensions
Width 319 mm
Height 215 mm
Depth 336 mm
Turntable diameter 272 mm
Control Complement
Touch Control System
Timer (0 - 99 minutes 90 seconds)
Clock (1:00 - 12:59) or (0:00 - 23:59)
Microwave Power for Variable Cooking
Repetition Rate;
100P ....................................................... Full power throughout the cooking time
70P .........................................................approx. 70% of FULL Power
50P ....................................................... approx. 50% of FULL Power
30P ........................................................approx. 30% of FULL Power
10P .........................................................approx. 10% of FULL Power
EXPRESS COOK button
EXPRESS DEFROST button
POWER LEVEL button
STOP/CLEAR button
START/AUTO MINUTE button
TIME/WEIGHT knob
Set Weight (Approx.) 12 kg
APPEARANCE VIEW
OVEN
1. Door opening handle
2. Oven lamp
3. Door hinges
4. Door safety latches
5. Door
6. Door seals and sealing surfaces
7. Coupling
9. Control panel
10. Waveguide cover
11. Power supply cord
12. Ventilation openings
13. Outer case cabinet
14. Turntable
15. Roller stay
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COOKMICRO
PCSKGTURNSTIR
1
3
4
5
6
7
8
9
2
TOUCH CONTROL PANEL
1. DIGITAL DISPLAY
2. INDICATORS
BUTTONS:
3. AUTO COOK
4. EXPRESS COOK
5. EXPRESS DEFROST
6. START/AUTO MINUTE
7. STOP/CLEAR
8. POWER LEVEL
9. TIME/WEIGHT KNOB
NOTE: Some one-touch cooking features such as "START/AUTO MINUTE" are
disabled after three minutes when the oven is not in use. These fea-
tures are automatically enabled when the door is opened and closed
or the STOP button is pressed.
OFF CONDITION
Closing the door activates all door interlock switches (1st. latch
switch, 2nd. interlock relay control switch).
IMPORTANT
When the oven door is closed, the monitor switch contacts
(COM-NC) must be open.
When the microwave oven is plugged in a wall outlet, rated volt-
age is supplied to the noise lter and the control unit.
Figure O-1 on page 20
The display will show ashing "88:88".
To set any programmes or set the clock, you must rst touch the
STOP/CLEAR button.
" : " appears in the display.
MICROWAVE COOKING CONDITION
HIGH COOKING
Enter a desired cooking time by rotating the TIME/WEIGHT
knob and start the oven with pressing START/AUTO MINUTE
button.
Function sequence Figure O-2 on page 20
CONNECTED COMPONENTS RELAY
Oven lamp, Fan motor, Turntable motor RY1
High voltage transformer RY2
Rated voltage is supplied to the primary winding of the high volt-
age transformer. The voltage is converted to about 3.3 volts A.C.
output on the lament winding and high voltage of approximately
2000 volts A.C. on the secondary winding
The filament winding voltage (3.3 volts) heats the magnetron
lament and the high voltage (2000 volts) is sent to the voltage
doubling circuit, where it is doubled to negative voltage of ap-
proximately 4000 volts D.C..
The 2450 MHz microwave energy produced in the magnetron
generates a wave length of 12.24 cm. This energy is channelled
OPERATION SEQUENCE
through the waveguide (transport channel) into the oven cavity,
where the food is placed to be cooked.
When the cooking time is up, a signal tone is heard and the re-
lays (RY1+RY2) go back to their home position. The circuits to
the oven lamp, high voltage transformer, fan motor and turntable
motor are cut off.
When the door is opened during a cook cycle, the switches
come to the following condition
SWITCH CONTACT
CONDITION
DURING
COOKING DOOR OPEN (NO COOKING)
1st. latch switch COM-NO Closed Open
2nd. interlock relay
control switch COM-NO Closed Open
Monitor switch COM-NC Open Closed
The circuits to the high voltage transformer, fan motor, turntable
motor and oven lamp are cut off when the 1st. latch switch and
2nd. interlock relay control switch are made open.
MONITOR SWITCH CIRCUIT
The monitor switch is mechanically controlled by oven door, and
monitors the operation of the 1st. latch switch, the relay (RY1)
and the 2nd. interlock relay (RY2).
When the oven door is opened during or after the cycle of a
cooking program, the 1st. latch switch and 2nd. interlock relay
control switch must open their contacts rst. After that the con-
tacts (COM-NC) of the monitor switch can be closed.
When the oven door is closed, the contacts (COM-NC) of the
monitor switch must be opened. After that the contacts of the
1st. latch switch and 2nd. interlock relay control switch are
closed.
When the oven door is opened and the contacts of the 1st. latch
switch, the relay (RY1) and the 2nd. interlock relay (RY1) remain
closed. The fuse T6.3A will blow, because the monitor switch is
closed and a short circuit is caused.
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100P (HIGH) 32 sec. ON
70P (MEDIUM
HIGH)
Approx. 70%
100%
24 sec. ON 8 sec. OFF
14 sec. OFF
20 sec. OFF
26 sec. OFF
50P (MEDIUM) Approx. 50%
18 sec. ON
30P (MEDIUM
LOW)
Approx. 30%
12 sec. ON
10P (LOW) Approx. 10%
6 sec. ON
Latch Heads
Latch Hook
Door
2nd. Interlock Relay
Control Switch
1st. Latch Switch
Monitor Switch
MEDIUM HIGH, MEDIUM, MEDIUM LOW, LOW
COOKING
When the microwave oven is preset for variable cooking power,
rated voltage is supplied to the high voltage transformer inter-
mittently within a 32 second time base through the relay contact
which is coupled with the current-limiting relay (RY2). The fol-
lowing levels of microwave power are given.
SETTING;
NOTE: The ON/OFF time ratio does not exactly correspond
to the percentage of microwave power, because ap-
prox. 3 seconds are needed for heating up the mag-
netron lament.
POWER OUTPUT REDUCTION
After 100% power cooking mode is carried out for more than
20 minutes, the power out-put is automatically reduced to 70%.
Even if the cooking time is shorter than for 20 minutes, the
power output is reduced to 70% after total cooking time over 20
minutes when the oven is started in 100% power cooking mode
again within 1 minute and 35 seconds.
DOOR OPEN MECHANISM
The door is opened by pulling the door, refer to the Figure D-1.
Figure D-1. Door Open Mechanism
1ST. LATCH SWITCH AND 2ND. INTER-
LOCK RELAY CONTROL SWITCH
When the oven door is closed, the contacts (COM-NO) must1. be closed.
When the oven door is opened, the contacts (COM-NO)2. must be opened.
MONITOR SWITCH
When the oven door is closed, the contacts (COM-NC) must1. be opened.
When the oven door is opened, the contacts (COM-NC)2. must be closed.
If the oven door is opened and the contacts (COM-NO) of3.
the 1st latch switch, the relay (RY1) and the 2nd. interlock
relay (RY2) fail to open, the fuse T6.3A blows simultaneous-
ly with closing the contacts (COM-NC) of the monitor switch.
CAUTION: BEFORE REPLACING A FUSE T6.3A TEST THE
1ST. LATCH SWITCH, RELAY (RY1) AND 2ND. IN-
TERLOCK RELAY (RY2) AND MONITOR SWITCH
FOR PROPER OPERATION. (REFER TO CHAP-
TER "TEST PROCEDURE".)
FUNCTION OF IMPORTANT COMPONENTS
FUSE T6.3A
The fuse T6.3A blows when the contacts (COM-NO) of the 11.
st. latch switch, the relay (RY1) and the 2nd. interlock relay
(RY2) remain closed with the oven door open and when the
monitor switch closes.
If the wire harness or electrical components are short-2.
circuited, the fuse T6.3A blows to prevent an electric shock
of re hazard.
HIGH VOLTAGE FUSE
The high voltage fuse blows when the high voltage rectier or
the magnetron is shorted.
TEMPERATURE FUSE 150°C (OVEN)
The temperature fuse located on the top of the oven cavity is
designed to prevent damage to the oven if the foods in the oven
catch fire due to over heating produced by improper setting
of cook time or failure of control unit. Under normal operation,
the temperature fuse remains closed. However, when abnor-
mally high temperatures are reached within the oven cavity, the
temperature fuse will open at 150°C, causing the oven to shut
down. The defective temperature fuse must be replaced with a
new one.
TURNTABLE MOTOR
The turntable motor drives the turntable roller assembly to ro-
tate the turntable.
FAN MOTOR
The fan motor drives a blade which draws external cool air. This
cool air is directed through the air vanes surrounding the mag-
netron and cools the magnetron. This air is channelled through
the oven cavity to remove steam and vapours given off from the
heating foods. It is then exhausted through the exhausting air
vents at the oven cavity.
NOISE FILTER
The noise filter prevents the radio frequency interference that
might ow back in the power circuit.
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MAGNETRON
HIGH VOLTAGE TRANSFORMER
H.V. RECTIFIER ASSEMBLY HIGH VOLTAGE WIRE HIGH VOLTAGE CAPACITOR
1ST. LATCH SWITCH 2ND. INTERLOCK RELAY CONTROL
SWITCH
MONITOR SWITCH TEMPERATURE FUSE 150ºC (OVEN)
FAN MOTOR TURNTABLE MOTOR
FUSE T6.3A TOUCH CONTROL PANEL RELAY (RY-1) RELAY (RY-2)
FOIL PATERN ON P.W.B. POWER SUPPLY CORD
SHORTED WIRE HARNESS OPENED WIRE HARNESS OVEN LAMP
WALL OUTLET MISADJUSTMENT SWITCH HOME FUSE OR BREAKER
BLOCKED COOLING FAN BLOCKED VENTILATION NOISE FILTER
SWITCH UNIT
H.V. FUSE
OFF
CONDITION
PROBLEM
CONDITION
POSSIBLE CAUSE
AND
DEFECTIVE PARTS
TEST PROCEDURE
ON
CONDITION
A B C
CK D EE E F G G H K M N I L JM RE CKCK RE CK CK CK CK CK
Home fuse blows when pow-
ersupply cord is plugged into
wall outlet.
FUSE T6.3A blows when
power supply cord is plug-
ged into wall outlet.
"88:88" does not appear in
display but power supply cord
is plugged into wall outlet.
Display does not operate
properly when STOP/CLEAR
button is pressed.
Oven does not start when the
START button is touched.
(Display appears)
Oven lamp does not light
(Display appears.)
Fan motor does not operate.
(Display appears.)
Turntable motor does not
operate. (Display appears.)
Oven or any electrical parts
does not stop when cooking
time is 0 or STOP button is
pressed.
Oven seems to be operating
but little or no heat is pro-
duced in oven load. (Micro-
wave power level is set at
100%)
Oven does not seems to be
operating properly when
70%,50%, 30% or 10% is
set. (Oven operates properly
at 100%.)
Oven goes into cook cycle
but shuts down before end
of cooking cycle.
TROUBLESHOOTING GUIDE
FOREWORD
When troubleshooting the microwave oven, it is helpful to follow
the Sequence of Operation in performing the checks. Many of
the possible causes of trouble will require that a specic test be
performed. These tests are given a procedure letter which will
be found in the "Test Procedure" section.
IMPORTANT:
If the oven becomes inoperative because of a blown fuse T6.3A
in the 1st. latch switch - relay (RY1) - 2nd. interlock relay (RY2)-
monitor switch circuit, check the 1st. latch switch, relay (RY1),
2nd. interlock relay (RY2) and monitor switch before replacing
the fuse T6.3A.
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TEST PROCEDURES
A: MAGNETRON TEST
NEVER TOUCH ANY PART IN THE CIRCUIT WITH YOUR HAND OR AN INSULATED TOOL WHILE THE OVEN IS
IN OPERATION.
CARRY OUT1. 3D CHECKS.
To test for an open lament, isolate the magnetron from the high voltage circuit. A continuity check across the magnetron lament 2. leads should indicate less than 1 ohm.
To test for a shorted magnetron, connect the ohmmeter leads between the magnetron lament leads and chassis ground. This test 3.
should indicate an innite resistance. If there is little or no resistance the magnetron is grounded and must be replaced.
Reconnect all leads removed from components during testing.4. Reinstall the outer case (cabinet).5. Reconnect the power supply cord after the outer case is installed.6.
Run the oven and check all functions.7.
MICROWAVE OUTPUT POWER
The following test procedure should be carried out with the microwave oven in a fully assembled condition (outer case tted).
The power output of this oven is rated using the method specied by IEC 60705. Full details of how to curry out this procedure can be
found in the Sharp Technical Training notes which is available from Sharp Parts Centre (part number SERV-LITMW01).
The IEC60705 procedure must be carried out using laboratory-type procedures and equipment.
These requirements make the procedure unsuitable for routine performance checks.
NOTE: The following test method gives an indication of the output power only, it cannot be used to establish the actual/rated
output power. If the true output power is required, then the IEC 60705 test method must be used.
Alternative simplied method:
Place 2 litres of cold water (between 12ºC and 20ºC) in a suitable container.1. Stir the water and measure the temperature in ºC. Note temperature as T1.2. Place the container in the microwave and heat the water for 1 minute and 48 seconds on full power.3.
NOTE: The operation time of microwave oven includes "3" sec. (3 sec. is magnetron lament heat-up time.)
When the 1 minute and 48 seconds is completed, remove the container and stir the water. Note the water temperature as T2.4. Calculate the output power using the following formula:5.
R.F. Power Output = (T2 - T1) x 80.
NOTE: The result from this test should be within the allowance of 2000cc alternative method. (±10%).
MICROWAVE LEAKAGE TEST
This oven should be tested for microwave leakage on completion of any repair or adjustment, following the procedure described in
the Sharp Technical Training notes (part number SERV-LITMW01). The maximum leakage permitted in BS EN 60335-2-25 is 50W/m2
(equivalent to 5W/m2), however it is not normal to detect any signicant leakage, therefore, any leakage which is detected should be
investigated.
It is essential that only leakage detectors with current calibration traceable to National Physical Laboratories are used.
Suitable leakage detectors: CELTEC A100
APOLLO X1
B: HIGH VOLTAGE TRANSFORMER TEST
WARNING: High voltage and large currents are present at the secondary winding and lament winding of the power trans-
former. It is very dangerous to work near this part when the oven is on. NEVER make any voltage measure-
ments of the high-voltage circuits, including the magnetron lament.
CARRY OUT1. 3D CHECKS.
Disconnect the leads to the primary winding of the high voltage transformer. Disconnect the lament and secondary winding con-2.
nections from the rest of the HV circuitry. Using an ohmmeter, set on a low range, it is possible to check the continuity of all three
winding. The following readings should be obtained:
a. Primary winding - - - - - - - - - 2.8 ohms approximately
b. Secondary winding-------204 ohms approximately
c. Filament winding - - - - - - - - - - - - - - less than 1 ohm
If the readings obtained are not stated as above, then the high voltage transformer is probably faulty and should be replaced.
Also, the high voltage transformer has the thermal cut-out in the primary coil. The thermal cut-out will open when the temperature3. of the thermal cut-out in the primary coil reaches approximately 150ºC. The thermal cut-out resets automatically at 130°C. If an
ohmmeter indicates an open circuit under normal condition, replace the high voltage transformer because the primary coil (thermal
cut-out) has opened. An open primary coil (thermal cut-out) indicates overheating of the high voltage transformer. Check for re-
stricted air ow to the high voltage transformer, especially the ventilation opening.
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9
CARRY OUT4. 4R CHECKS.
C: HIGH VOLTAGE RECTIFIER TEST
CARRY OUT 3D CHECKS.
Isolate the high voltage rectier assembly from the HV circuit. The high voltage rectier can be tested using an ohmmeter set to its
highest range. Connect the ohmmeter across the terminal of the high voltage rectier and note the reading obtained. Reverse the me-
ter leads and note this second reading. The normal resistance is innite in one direction and more than 100 kW in the other direction.
CARRY OUT 4R CHECKS.
NOTE:FOR MEASUREMENT OF THE RESISTANCE OF THE RECTIFIER, THE BATTERIES OF THE MEASURING
INSTRUMENT MUST HAVE A VOLTAGE AT LEAST 6 VOLTS, BECAUSE OTHERWISE AN INFINITE RESIST-
ANCE MIGHT BE SHOWN IN BOTH DIRECTION.
D: HIGH VOLTAGE CAPACITOR TEST
CARRY OUT 3D CHECKS.
Isolate the high voltage capacitor from the circuit.1.
Continuity check must be carried out with measuring instrument which is set to the highest resistance range.2.
A normal capacitor shows continuity for a short time (kick) and then a resistance of about 10MW after it has been charged.3. A short-circuited capacitor shows continuity all the time.4. An open capacitor constantly shows a resistance about 10 MW because of its internal 10MW resistance.5.
When the internal wire is opened in the high voltage capacitor shows an innite resistance.6.
The resistance across all the terminals and the chassis must be innite when the capacitor is normal.7.
If incorrect reading are obtained, the high voltage capacitor must be replaced.
CARRY OUT 4R CHECKS.
E: SWITCH TEST
CARRY OUT 3D CHECKS.
Isolate the switch to be tested and using an ohmmeter check between the terminals as described in the following table.
Table: Terminal Connection of Switch
Plunger Operation Common terminal to Normally open terminal Common terminal to Normally close terminal
Released Open circuit Short circuit
Depressed Short circuit Open circuit.
If incorrect readings are obtained, make the necessary switch adjustment or replace the switch.
CARRY OUT 4R CHECKS.
F: TEMPERATURE FUSE TEST
CARRY OUT 3D CHECKS.
Disconnect the leads from the terminals of the temperature fuse. Then using an ohmmeter, make a continuity test across the two ter-
minals as described in the below.
Table: Temperature Fuse Test
Parts Name Temperature of "ON" condition
(Closed circuit). Temperature of "OFF" condition (Open circuit). Indication of ohmmeter (When room temperature is approx. 20°C.)
Temperature fuse 150°C This is not resetable type. Above 150°C Closed circuit
If incorrect readings are obtained, replace the temperature fuse.
An open circuit temperature fuse (OVEN) indicates that the food in the oven cavity may catch re, this may be due to overheating pro-
duced by improper setting of the cooking time or failure of the control panel.
CARRY OUT 4R CHECKS.
G: MOTOR WINDING TEST
CARRY OUT 3D CHECKS.
Disconnect the leads from the motor. Using an ohmmeter, check the resistance between the two terminals as described in the table
below. Table: Resistance of Motor
Motors Resistance
Fan motor Approximately 250 W
Turntable motor Approximately 14.7 kW
If incorrect readings are obtained, replace the motor. CARRY OUT 4R CHECKS.
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10
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H: FUSE T6.3A
CARRY OUT 3D CHECKS.
If the fuse T6.3A is blown when the door is opened, check the 1st. latch switch, relay (RY1), 2nd. interlock relay (RY2) and monitor
switch.
If the fuse T6.3Ais blown by incorrect door switching replace the defective switch(es) and the fuse T6.3A.
If the fuse T6.3A is blown, there is a shorts or grounds in electrical parts or wire harness. Check them and replace the defective parts
or repair the wire harness.
CARRY OUT 4R CHECKS.
CAUTION: ONLY REPLACE FUSE T6.3A WITH THE CORRECT VALUE REPLACEMENT.
I: NOISE FILTER TEST
CARRY OUT 3D CHECKS.
Disconnect the leads from the terminals of the noise lter. Using an ohmme-
ter, check between the terminals as described in the following table.
MEASURING POINT INDICATION OF OHMMETER
Between N and L Open circuit
Between terminal N and WHITE Short circuit
Between terminal L and RED Short circuit
If incorrect readings are obtained, replace the noise lter unit.
CARRY OUT 4R CHECKS.
J: HIGH VOLTAGE FUSE TEST
CARRY OUT 3D CHECKS.
If the high voltage fuse is blown, there could be a short in the high voltage rectier or the magnetron.
Check them and replace the defective parts and the high voltage fuse.
CARRY OUT 4R CHECKS.
CAUTION: ONLY REPLACE HIGH VOLTAGE FUSE WITH THE CORRECT VALUE REPLACEMENT.
K: TOUCH CONTROL PANEL ASSEMBLY TEST
The touch control panel consists of circuits including semiconductors such as LSI, ICs, etc. Therefore, unlike conventional microwave
ovens, proper maintenance cannot be performed with only a voltmeter and ohmmeter. In this service manual, the touch control panel
assembly is divided into two units, Control Unit and Switch Unit, and also the Control Unit is divided into two units, CPU Unit and Pow-
er Unit, and troubleshooting by unit replacement is described according to the symptoms indicated.
1. Switch Unit. Note: Check switch unit wire harness connection before replacement.
The following symptoms indicate a defective switch unit. Replace the switch unit.
a) When touching the buttons, a certain button produces no signal at all.
b) When touching the buttons, sometimes a button produces no signal.
c) When rotating the TIMER/WEIGHT knob, the cooking time or the weight can not be input.
2. Control Unit.
The following symptoms indicate a defective control unit. Before replacing the switch unit, perform the Switch unit test (Procedure L)
to determine if control unit is faulty.
2-1. In connection with buttons.
a) When touching the buttons, a certain group of buttons do not produce a signal.
b) When touching the buttons, no buttons produce a signal.
2-2. In connection with indicators.
a) At a certain digit, all or some segments do not light up.
b) At a certain digit, brightness is low.
c) Only one indicator does not light up.
d) The corresponding segments of all digits do not light up; or they continue to light up.
e) Wrong gure appears.
f) A certain group of indicators do not light up.
g) The gure of all digits icker.
3. Other possible troubles caused by defective control unit.
a) Buzzer does not sound or continues to sound.
b) Clock does not operate properly.
c) Cooking is not possible.
RED
WHT
FUSE
T6.3A
NL
NOISE SUPPRESSION COIL
NOISE FILTER
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11
L: SWITCH UNIT TEST
CARRY OUT1. 3D CHECKS.
Isolate the switch unit with the control panel frame to be tested.2.
Using an ohmmeter and referring to the switch unit matrix indicated on the switch unit circuit, check the circuit between the pins of 3. the switch unit that correspond to the STOP button. When the button is pressed, the ohmmeter should indicate short circuit. When
the button is released, the ohmmeter should indicate open circuit. If incorrect readings are obtained, the switch unit button is faulty
and must be replaced. About the other buttons, the above method may be used.
CARRY OUT4. 4R CHECKS.
A-3 A-4 A-5 A-6
B-2
B-3
A-1
A
B
C
SW100
A-2
C100
C101
R100
R101
A-7
B-1
C-1 C-2 C-3
3PIN
WIRE
HARNESS
SWITCH UNIT
EXPRESS
COOK
MEAT
JOINT
TIME
WEIGHT
MINCED
MEAT
WHOLE
POULTRY
POWER
LEVEL STOP
CLEAR
START
AUTO
MINUTE
SW1
SW2
SW3
SW4
SW5
SW6
SW7
M: RELAY TEST
CARRY OUT 3D CHECKS.
Remove the outer case and check voltage between the upper side terminal of the relay RY1 and the oven side terminal of the relay
RY2 on the control unit with an A.C. voltmeter. The meter should indicate 230 - 240 volts, if not check oven circuit.
RY1 and RY2 Relay Test
These relays are operated by D.C. voltage
Check voltage at the relay coil with a D.C. voltmeter during the microwave cooking operation.
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. 12.6V D.C. Oven lamp / Turntable motor / Cooling fan motor
RY2 Approx. 12.1V D.C. High voltage transformer
CARRY OUT 4R CHECKS.
N: PROCEDURES TO BE TAKEN WHEN THE FOIL PATTERN ON THE PRINTED WIRING BOARD (PWB)
IS OPEN
To protect the electronic circuits, this model is provided with a ne foil pattern added to the primary on the PWB, this foil pattern acts
as a fuse. If the foil pattern is open, follow the troubleshooting guide given below for repair.
Problem: POWER ON, indicator does not light up.
CARRY OUT 3D CHECKS.
STEPS OCCURRENCE CAUSE OR CORRECTION
1The rated AC voltage is not present between the upper side terminal of
the relay RY1 and the oven side terminal of the relay RY2. Check supply voltage and oven power cord.
2The rated AC voltage is present to primary side of low voltage transformer. Low voltage transformer or secondary circuit defective.
Check and repair.
3Only pattern at "a" is broken. *Insert jumper wire J1 and solder.
4Pattern at "a" and "b" are broken. *Insert the coil RCILF2003YAZZ between "c" and "d".
NOTE: *At the time of making these repairs, make a visual inspection of the varistor. Check for burned damage and examine
the transformer with a tester for the presence of layer short-circuit (check the primary coil resistance). If any abnor-
mal condition is detected, replace the defective parts.
CARRY OUT 4R CHECKS.
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12
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TOUCH CONTROL PANEL ASSEMBLY
OUTLINE OF TOUCH CONTROL PANEL
The touch control section consists of the following units as shown in the touch control panel circuit.
(1) Switch Unit
(2) Control Unit
The principal functions of these units and their related signals are explained below.
Switch Unit
The switch unit is composed of a matrix, signals generated in the LSI are sent to the switch unit through P22, P24, P25 and P26.
When a button is pressed, a signal is completed through the switch unit and passed back to the LSI through P50 and P52 to perform
the function that was requested. When the jog dial is rotated, the encoder converts the signal from the power source circuit into the
pulse signal, and the pulse signal is sent to the LSI through P31 and P32.
Control Unit
Control unit consists of LSI, reset circuit, indicator circuit, power source circuit, relay circuit, buzzer circuit and synchronizing signal cir-
cuit.
1) Reset Circuit
This circuit generates a signal which resets the LSI to the initial state when power is supplied.
2) Indicator Circuit
This circuit consists of 4-digits, 12-segments and 3-common electrodes using a Liquid Crystal Display.
3) Power Source Circuit
This circuit generates voltage necessary in the control unit from the AC line voltage. In addition, the synchronizing signal is
available in order to compose a basic standard time in the clock circuit.
Symbol Voltage Application
VSS -5V LSI(IC1)
4) Relay Circuit
To drive the magnetron, fan motor, turntable motor and light the oven lamp.
5) Buzzer Circuit
The buzzer is responsive to signals from the LSI to emit audible sounds (switch unit touch sound and completion sound).
6) Synchronizing Signal Circuit
The power source synchronizing signal is available in order to compose a basic standard time in the clock circuit. It accompanies
a very small error because it works on commercial frequency.
7) 2nd. Interlock Relay Control Switch
A switch to "tell" the LSI if the door is open or closed.
8) Back Light Circuit
A circuit to drive the back light (Light emitting diodes LD1 - LD4).
SERVICING FOR TOUCH CONTROL PANEL
1. Precautions for Handling Electronic Components
This unit uses CMOS LSI in the integral part of the circuits.
When handling these parts, the following precautions should
be strictly followed. CMOS LSI have extremely high impedance
at its input and output terminals. For this reason, it is easily in-
uenced by the surrounding high voltage power source, static
electricity charge in clothes, etc., and sometimes it is not fully
protected by the built-in protection circuit.
In order to protect CMOS LSI.
1) When storing and transporting, thoroughly wrap them in
aluminium foil. Also wrap PW boards containing them in
aluminium foil.
2) When soldering, ground the technician as shown in the
gure and use grounded soldering iron and work table.
approx. 1M ohm
2. Servicing of Touch Control Panel
We describe the procedures to permit servicing of the touch
control panel of the microwave oven and the precautions you
must take when doing so. To perform the servicing, power to the
touch control panel is available either from the power line of the
oven itself or from an external power source.
1) Servicing the touch control panel with power supply of
the oven:
CAUTION: THE HIGH VOLTAGE TRANSFORMER OF THE MI-
CROWAVE OVEN IS STILL LIVE DURING SERVIC-
ING AND PRESENTS A HAZARD.
Therefore, before checking the performance of the touch
control panel,
(1) Disconnect the power supply cord and then remove
outer case.
(2) Open the door and block it open.
Discharge high voltage capacitor.
(3) Disconnect the leads to the primary of the power
transformer.
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13
(4) Ensure that these leads remain isolated from other
components and oven chassis by using insulation tape.
After that procedure, re-connect the power supply cord.
(1) After checking the performance of the touch control
panel,
(2) Disconnect the power supply cord.
Open the door and block it open.
(3) Re-connect the leads to the primary of the power
transformer.
(4) Re-install the outer case (cabinet).
Re-connect the power supply cord after the outer case
is installed.
Run the oven and check all functions.
AOn some models, the power supply cord between the
touch control panel and the oven itself is so short that
the two can't be separated. For those models, check
and repair all the controls (sensor-related ones included)
of the touch control panel while keeping it connected to
the oven.
BOn some models, the power supply cord between the
touch control panel and the oven proper is so long
enough that they may be separated from each other.
For those models, therefore, it is possible to check
and repair the controls of the touch control panel while
keeping it apart from the oven proper; in this case you
must short both ends of the door sensing switch (on
PWB) of the touch control panel with a jumper, which
brings about an operational state that is equivalent to
the oven door being closed. As for the sensor-related
controls of the touch control panel, checking them is
possible if the dummy resistor(s) with resistance equal
to that of the controls are used.
2) Servicing the touch control panel with power supply from an
external power source:
Disconnect the touch control panel completely from the
oven proper, and short both ends of the door sensing switch
(on PWB) of the touch control panel, which brings about an
operational state that is equivalent to the oven door being
closed. 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
touch 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
terminal.)
2) Oscilloscope: Single beam, frequency range: DC - 10MHz
type or more advanced model.
3) Others: Hand tools
4. Other Precautions
1) Before turning on the power source of the control unit,
remove the aluminium foil applied for preventing static
electricity.
2) Connect the connector of the key unit to the control unit
being sure that the lead wires are not twisted.
3) After aluminium foil is removed, be careful that abnormal
voltage due to static electricity etc. is not applied to the input
or output terminals.
4) Attach connectors, electrolytic capacitors, etc. to PWB,
making sure that all connections are tight.
5) Be sure to use specied components where high precision
is required.
PRECAUTIONS FOR USING LEAD-FREE SOLDER
1. Employing lead-free solder
The "Main PWB" of this model employs lead-free solder. This is indicated by the "LF" symbol printed on the PWB and in the service
manual. The sufx letter indicates the alloy type of the solder.
Example:
Indicates lead-free solder of tin, silver and copper
2. Using lead-free wire solder
When repairing a PWB with the "LF" symbol, only lead-free solder should be used. (Using normal tin/lead alloy solder may result in
cold soldered joints and damage to printed patterns.)
As the melting point of lead-free solder is approximately 40ºC higher than tin/lead alloy solder, it is recommend that a dedicated bit is
used, and that the iron temperature is adjusted accordingly.
3. Soldering
As the melting point of lead-free solder (Sn-Ag-Cu) is higher and has poorer wettability, (ow), to prevent damage to the land of the
PWB, extreme care should be taken not to leave the bit in contact with the PWB for an extended period of time. Remove the bit as
soon as a good ow is achieved. The high content of tin in lead free solder will cause premature corrosion of the bit. To reduce wear
on the bit, reduce the temperature or turn off the iron when it is not required.
Leaving different types of solder on the bit will cause contamination of the different alloys, which will alter their characteristics, making
good soldering more difcult. It will be necessary to clean and replace bits more often when using lead-free solder. To reduce bit wear,
care should be taken to clean the bit thoroughly after each use.
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14
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WARNING AGAINST HIGH VOLTAGE:
Microwave ovens contain circuitry capable of producing very high voltage and current, contact with following parts may result in se-
vere, possibly fatal, electric shock.
(Example)
High Voltage Capacitor, High Voltage Transformer, Magnetron, High Voltage Rectier Assembly, High Voltage fuse, High Voltage
Harness etc..
WARNING: Avoid possible exposure to microwave energy. Please follow the instructions
below before operating the oven.
COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE
Disconnect the power supply cord.1.
Visually check the door and cavity face plate for damage 2.
(dents, cracks, signs of arcing etc.).
Carry out any remedial work that is necessary before operat-
ing the oven.
Do not operate the oven if any of the following conditions exist;
Door does not close rmly.1.
Door hinge, support or latch hook is damaged.2.
The door gasket or seal is damaged.3. The door is bent or warped.4.
WARNING FOR WIRING
There are defective parts in the door interlock system.5. There are defective parts in the microwave generating and6. transmission assembly.
There is visible damage to the oven.7.
Do not operate the oven:
Without the RF gasket (Magnetron).1. If the wave guide or oven cavity are not intact.2. If the door is not closed.3.
If the outer case (cabinet) is not tted.4.
To prevent an electric shock, take the following manners.
Before wiring,1. Disconnect the power supply cord.1)
Open the door and block it open.2) Discharge the high voltage capacitor and wait for 603) seconds.
Don't let the wire leads touch to the following parts;1. High voltage parts:1) Magnetron, High voltage transformer, High voltage ca-
pacitor, High voltage rectier assembly and High volt-
age fuse.
Hot parts:2) Oven lamp, Magnetron, High voltage transformer and
Oven cavity.
Sharp edge:3)
Bottom plate, Oven cavity, Waveguide ange and other
metallic plate.
Movable parts (to prevent a fault)4) Fan blade, Fan motor, Turntable motor and Switch.
Do not catch the wire leads in the outer case cabinet.1.
Insert the positive lock connector certainly until its pin is 2.
locked and make sure that the wire leads do not come off
even if the wire leads are pulled.
To prevent an error function, connect the wire leads cor-3. rectly, referring to the Pictorial Diagram.
Please refer to `OVEN PARTS, CABINET PARTS, CONTROL PANEL PARTS, DOOR PARTS', when carrying out any of the following
removal procedures:
REMEMBER TO CHECK 3D
1) Disconnect the supply.
2) Door opened, and wedged open.
3) Discharge high voltage capacitor.
OUTER CASE REMOVAL
To remove the outer case, procedure as follows.
Disconnect the oven from power supply.1. Open the oven door and wedge it open.2. Remove the two (2) screws from right side of the outer case3. cabinet.
Remove the five (5) screws from rear and along the side4. edge of case.
Slide the entire case back about 3cm to free it from retaining 5.
clips on the cavity face plate.
Lift the entire case from the oven.6. Discharge the H. V. capacitor before carrying out any further7.
work.
Do not operate the oven with the outer case removed.8.
NOTE: Step 1, 2 and 7 form the basis of the 3D checks.
CAUTION: DISCONNECT OVEN FROM POWER SUPPLY BE-
FORE REMOVING OUTER CASE.
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15
CARRY OUT1. 3D CHECKS.
Disconnect the wire leads (main wire harness and H. V.2. fuse) from high voltage transformer.
Disconnect the filament lead of high voltage transformer3. from the magnetron.
Disconnect the lament lead of the high voltage transformer 4.
from high voltage capacitor.
Remove the two (2) screws holding the transformer to bot-5. tom plate from below.
Remove the two (2) screws holding the transformer to bot-6. tom plate from above.
Remove the transformer.7.
HIGH VOLTAGE TRANSFORMER REMOVAL
er assembly from high voltage capacitor.
Disconnect the H. V. fuse from the high voltage capacitor.8.
Now H. V. rectier assembly, H. V. fuse and H. V. capacitor 9. should be free.
CAUTION: WHEN REPLACING HIGH VOLTAGE RECTI-
FIER ASSEMBLY, ENSURE THAT THE CATHODE
(EARTH) CONNECTION IS SECURELY FIXED TO
THE CAPACITOR HOLDER WITH AN EARTHING
SCREW.
CAUTION: DO NOT REPLACE ONLY HIGH VOLTAGE REC-
TIFIER. WHEN REPLACING IT, REPLACE HIGH
VOLTAGE RECTIFIER ASSEMBLY.
HIGH VOLTAGE RECTIFIER ASSEMBLY, HIGH VOLTAGE FUSE AND HIGH VOLTAGE CAPACITOR REMOVAL
To remove the components, proceed as follows.
CARRY OUT1. 3D CHECKS.
Disconnect the H. V. fuse from the high voltage transformer.2.
Disconnect the H. V. wire of the H. V. rectier assembly from 3. the magnetron.
Disconnect the lament lead of the high voltage transformer 4. from the H. V. capacitor.
Remove one (1) screw holding capacitor holder to the oven5.
cavity back plate.
Remove one (1) screw holding earth side terminal of high6.
voltage rectier assembly, and remove capacitor holder.
Disconnect all the leads and terminals of high voltage recti-7.
MAGNETRON REMOVAL
REMOVAL
CARRY OUT1. 3D CHECKS.
Disconnect the wire leads from the magnetron.2. Remove the two (2) screws holding the air duct to the oven3. cavity.
Release the air duct from the oven cavity.4. Carefully remove the four (4) screws holding the magnetron5.
to the waveguide ange.
Lift up magnetron with care so that the magnetron antenna6. is not hit by any metal object around antenna.
Now, the magnetron is free.7.
REINSTALLATION
Reinstall the magnetron to the waveguide flange with the1. four (4) screws.
Reinstall the air duct to the oven cavity with the two (2)2. screws.
Reconnect the wire leads to the magnetron. Refer to "PIC-3.
TORIAL DIAGRAM".
Reinstall the outer case and check that the oven is operating 4. properly.
CAUTION: WHEN REPLACING THE MAGNETRON, BE SURE
THE R. F. GASKET IS IN PLACE AND THE MAGN-
ETRON MOUNTING SCREWS ARE TIGHTENED
SECURELY.
POSITIVE LOCK CONNECTOR (NO-CASE TYPE) REMOVAL
CARRY OUT1. 3D CHECKS.
Push the lever of positive lock, connector.2.
Pull down on the positive lock, connector.3.
CAUTION: WHEN CONNECTING THE POSITIVE LOCK, CON-
NECTORS TO THE TERMINALS, CONNECT THE
POSITIVE LOCK, SO THAT THE LEVER FACES
YOU.
Terminal
Push
Pull down
1
2
Lever
Positive lock¨
connector
Figure C-1. Positive lock, connector
TURNTABLE MOTOR REMOVAL
REMOVAL
Disconnect the power supply cord.1. Remove turntable and turntable support from oven cavity.2.
Lay the oven on it's backside. Remove the turntable motor 3. cover by snipping off the material in four corners.
Where the corners have been snipped off bend corner areas4. flat. No sharp edges must be evident after removal of the
turntable motor cover.
Disconnect wire leads from turntable motor. (See "Positive 5.
lock connector removal")
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16
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Remove one (1) screw holding turntable motor to oven cav-6. ity.
Remove the TTM packing from the turntable motor.7. Now, the turntable motor is free.8.
REINSTALL
Re-install the TTM packing to the turntable motor.1.
Re-install the turntable motor with the TTM packing with the 2. single (1) screw to the oven cavity bottom plate.
Re-connect the wire leads to the turntable motor.3. Insert the tab of the turntable motor cover into the hole of4. the bottom plate.
Re-install the turntable motor cover to the bottom plate with5. one (1) screw.
TTM packing
Turntable motor
Figure C-2. TTM packing Installation
COOLING FAN MOTOR REMOVAL
REMOVAL
CARRY OUT1. 3D CHECKS.
Disconnect the wire leads from the fan motor.2. Remove the two (2) screws holding the fan motor to the3.
oven cavity back plate.
Remove the fan blade from the fan motor shaft according to4. the following procedure.
Hold the edge of the rotor of the fan motor by using a pair of5. groove joint pliers.
CAUTION: MAKE SURE THAT ANY PIECES DO NOT ENTER
THE GAP BETWEEN THE ROTOR AND THE STA-
TOR OF THE FAN MOTOR. BECAUSE THE RO-
TOR IS EASY TO BE SHAVEN BY PLIERS AND
METAL PIECES MAY BE PRODUCED.
DO NOT TOUCH THE PLIERS TO THE COIL OF
THE FAN MOTOR BECAUSE THE COIL MAY BE
CUT OR INJURED.
DO NOT DISFIGURE THE BRACKET BY TOUCH-
ING WITH THE PLIERS.
Remove the fan blade from the shaft of the fan motor by6. pulling and rotating the fan blade with your hand.
Now, the fan blade will be free.7.
CAUTION: DO NOT RE-USE THE REMOVED FAN BLADE BE-
CAUSE THE HOLE (FOR SHAFT) MAY BE LARG-
ER THAN NORMAL.
Now, the fan motor is free.8.
INSTALLATION
Install the fan blade to the fan motor shaft according to the1. following procedure.
Hold the centre of the bracket which supports the shaft of 2.
the fan motor on the at table.
Apply the screw lock tight into the hole (for shaft) of the fan 3. blade.
Install the fan blade to the shaft of fan motor by pushing the4. fan blade with a small, light weight, ball peen hammer or
rubber mallet.
CAUTION: DO NOT HIT THE FAN BLADE STRONGLY WHEN
INSTALLED BECAUSE THE BRACKET MAY BE
TRANSFORMED.
MAKE SURE THAT THE FAN BLADE ROTATES
SMOOTH AFTER INSTALLED.
MAKE SURE THAT THE AXIS OF THE SHAFT IS
NOT SLANTED.
Install the fan motor assembly to the oven cavity back plate 5. with two (2) screws.
Connect the wire leads to the magnetron and fan motor, re-6. ferring to the pictorial diagram.
Gap Rotor
Bracket
Stator
Groove joint pliers
Coil
Shaft
Axis Stator
Rotor
These are the positions
that should be pinched
with pliers.
Shaft
Table Center of
bracket
Rear View Side View
REMOVAL
CARRY OUT1. 3D CHECKS.
Remove the single (1) screw holding the green/yellow wire2.
to the oven cavity back plate.
Disconnect the leads of the power supply cord from the3.
noise lter, referring to the Figure C-3(a).
Release the moulding cord stopper of the power supply cord4. from
the square hole of the oven cavity back plate, referring to 5. the Figure C-3 (b).
POWER SUPPLY CORD REPLACEMENT
Now, the power supply cord is free.6.
REINSTALL
Insert the moulding cord stopper of power supply cord into1. the square hole of the rear cabinet, referring to the Figure
C-3 (b).
Install the earth wire lead of power supply cord to the oven2.
cavity back plate with one (1) screw and tight the screw.
Connect the brown and blue wire leads of power supply cord3.
to the noise lter correctly, referring to the Pictorial Diagram.
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17
CARRY OUT 3D CHECKS.
Disconnect the leads from the control unit.1. Remove the one (1) screw holding the control panel to the2. front panel of the oven cavity.
Lift up the control panel assembly and release it from the3. oven cavity.
Now, the control panel assembly is free.4.
Figure C-3(a) Power Supply Cord Replacement Figure C-3(b) Power Supply Cord Replacement
CONTROL PANEL ASSEMBLY REMOVAL
NL
Power Supply
Cord Oven Cavity
Back Plate
Screw
Green/Yellow
Wire
Brown Wire
Blue
Wire Noise Filter
WHT
RED
P ower S upply
C ord
Oven C avity
B ack P late
S quare
Hole
Moulding
C ord S topper
1ST. LATCH SWITCH, 2ND. INTERLOCK RELAY CONTROL SWITCH AND MONITOR SWITCH REPLACEMENT
REMOVAL
CARRY OUT 3D CHECKS.1. Remove the control panel assembly, referring to section of2. CONTROL PANELASSEMBLY REMOVAL.
Disconnect wire leads from the switches.3.
Remove two (2) screws holding latch hook to oven ange.4.
Remove latch hook assembly from oven ange.5. Push outward on the two (2) retaining tabs holding switch in6. place.
Switch is now free.7.
REINSTALL
Re-install each switch in its place. The 1st. latch switch and1.
the monitor switch are in the lower position and the 2nd. in-
terlock relay control switch is in the upper position
Secure latch hook (with two (2) mounting screws) to oven 2.
ange.
Re-connect wire leads to each switch. Refer to pictorial dia-3. gram.
Reinstall the control panel assembly to the oven cavity.4. Reconnect wire leads to the control unit, referring to the pic-5. torial diagram.
Make sure that the monitor switch is operating properly and 6.
check continuity of the monitor circuit. Refer to chapter "Test
Procedure" and Adjustment procedure.
1ST. LATCH SWITCH, 2ND. INTERLOCK RELAY CONTROL SWITCH AND MONITOR SWITCH ADJUSTMENT
CARRY OUT1. 3D CHECKS.
If the 1st. latch switch, 2nd. interlock relay control switch and 2. monitor switch do not operate properly due to a misadjust-
ment, the following adjustment should be made.
Loosen the two (2) screws holding latch hook to the oven 3.
cavity front ange.
With door closed, adjust latch hook by moving it back and 4. forth, and up and down. In and out play of the door allowed
by the upper and lower position of the latch hook should
be less than 0.5mm. The vertical position of the latch hook
should be adjusted so that the 1st. latch switch and 2nd.
interlock relay control switch are activated with the door
closed. The horizontal position of the latch hook should be
adjusted so that the plunger of the monitor switch is pressed
with the door closed.
Secure the screws with washers rmly.5.
Check the operation of all switches. If each switch has not 6. activated with the door closed, loosen screw and adjust the
latch hook position.
After adjustment, check the following.
In and out play of door remains less than 0.5mm when in the1.
latched position. First check upper position of latch hook,
pushing and pulling upper portion of door toward the oven
face. Then check lower portion of the latch hook, pushing
and pulling lower portion of the door toward the oven face.
Both results (play in the door) should be less than 0.5mm.
When the door is open, the contacts of the 1st. latch switch2.
and 2nd. interlock relay control switch open within 1.6mm
gap between right side of cavity face and the door.
Monitor switch contacts close when door is opened.3.
Re-install outer case and check for microwave leakage 4. around door with an approved microwave survey meter.
(Refer to Microwave Measurement Procedure.)
Latch Heads
Latch Hook
Door
2nd. Interlock Relay
Control Switch
1st. Latch Switch
Monitor Switch
Figure C-5. Latch Switch Adjustments
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18
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DOOR REPLACEMENT
REMOVAL
Disconnect the power supply cord.1. Open the door slightly.2.
Insert a putty knife (thickness of about 0.5mm) into the gap 3.
between the choke cover and corner portion of door panel
as shown in Figure C-6 to free engaging parts.
Pry the choke cover by inserting a putty knife as shown Fig-4. ure C-6.
Release choke cover from door panel.5.
Now choke cover is free.6.
NOTE: When carrying out any repair to the door, do not
bend or warp the slit choke (tabs on the door panel
assembly) to prevent microwave leakage.
Choke Cover
Door Frame
Putty Knife
Figure C-6. Door Disassembly
Release two (2) pins of door panel from two (2) holes of up-7. per and lower oven hinges by lifting up.
Now, door panel with door frame is free from oven cavity.8. Release door panel from ten (10) tabs of door frame and re-9. move the door frame by sliding the door panel downward.
Now, door panel with sealer lm is free.10.
Tear sealer lm from door panel.11. Now, door panel is free.12.Slide latch head upward and remove it from door frame with13. releasing latch spring from door frame and latch head.
Now, latch head and latch spring are free.14.Remove the two (2) screws holding the door handle15.and the glass stopper to the door frame.
Remove the door handle and the glass stopper from16.the door frame.
Slide the door glass towards the door glass stopper17.position and then down towards the lower edge of the door
frame.
Lift the upper edge of the door glass, which will now be18.free from the upper clips and remove from lower clips.
Now, door glass is free.19.
REINSTALLATION
Insert door glass into the door frame by reversing the above1. door glass removing procedure.
Re-install the glass stopper and the door handle to the door2. frame with the two (2) screws.
Re-install latch spring to the head. Re-install latch spring to3. the door frame. Re-install latch head to the door frame.
Re-install door panel to door frame by tting ten (10) tabs of 4. door frame to ten (10) holes of door panel.
Put sealer lm on door panel. Refer to "Sealer Film" about 5. how to handle new one.
Catch two (2) pins of door panel on two (2) hole of upper6. and lower oven hinges
Re-install choke cover to door panel by pushing.7.
NOTE: After any service to the door;
Make sure that 1st. latch switch, 2nd. interlock relay
control switch and monitor switch are operating
properly. (Refer to chapter "Test Procedures".).
An approved microwave survey meter should be
used to assure compliance with proper microwave
radiation emission limitation standards.
After any service, make sure of the following:
Door latch heads smoothly catch latch hook through latch 1. holes and that latch head goes through centre of latch hole.
Deviation of door alignment from horizontal line of cavity 2. face plate is to be less than 1.0mm.
Door is positioned with its face pressed toward cavity face3. plate.
Check for microwave leakage around door with an approved 4. microwave survey meter. (Refer to Microwave Measurement
Procedure).
NOTE: The door on a microwave oven is designed to act
as an electronic seal preventing the leakage of mi-
crowave energy from oven cavity during cook cycle.
This function does not require that door be air-tight,
moisture (condensation) tight or light-tight. There-
fore, occasional appearance of moisture, light or
sensing of gentle warm air movement around oven
door is not abnormal and do not of themselves,
indicate a leakage of microwave energy from oven
cavity.
Upper Oven
Hinge
Lower
Oven Hinge
Pin
Upper
Oven Hinge
Slit choke of
door panel
Choke Cover
Pin
Lower Oven
Hinge
Figure C-7. Door Replacement
SEALER FILM
Put the adhesive tape on the backing lm of the sealer lm as
shown in Fig. C-8
Tear the backing lm by pulling the adhesive tape.
Put the pasted side of the sealer lm on the door panel
Sealer film Backing film
Adhesive tape
Figure C-8. Sealer lm
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R-27STM
19
MICROWAVE MEASUREMENT
After any repair, the microwave oven must be checked for microwave leakage to ensure continued safe operation. BS EN 60335-2-25
species that the maximum permitted leakage with a load of 275 ml is 50 W/m2(equivalent to 5 mW/cm2) at a distance of 5 cm from
the oven.
PREPARATION
The following items are required to carry out this test:
A low form of 600 ml beaker made from an electrically non-conductive material, such as glass or plastic, with an inside diameter of 1. approximately 8.5 cm. This must contain 275 ± 15 ml of water, at an initial temperature of 20 ± 2ºC.
A leakage detector which has been calibrated within the preceding 12 months to a stand whose accuracy can be traced to Nation-2. al Physical Laboratory Standards.
Recommended instruments are:-
Apollo "XI"
Celtec "A100"
Before commencing the test, check that the leakage detector is functioning and adjusted according to the manufacturer's instructions,
and any spacers are tted to ensure that measurement is taken 5cm from the surface of the oven.
PROCEDURE
Place the beaker containing the water load in the oven cavity at the centre of the turntable. The placing of this standard load in the 1.
oven is important, not only to protect the oven, but also to ensure that any leakage it is not disguised by too large a load absorbing
energy.
Close the oven door, and with the power level set to FULL, turn the oven ON with the timer set for a few minutes operation. Should2. the water begin to boil before the test has been completed, it should be replaced.
As shown in the diagram below, move the probe slowly (not faster than 2.5 cm/sec.);-3. around the edge of the door following the gap1) across the face of the door2) across any vents in the oven's sides, rear or top3)
Dotted line indicates the path taken by the leakage detector.
Whilst the maximum leakage permitted in BS EN 60335-2-25 is 50 W/m2(equivalent to 5 mW/cm2), it is not normal to detect
any signicant leakage, and therefore any detected leakage should be investigated.
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20
R-27STM
CIRCUIT DIAGRAMS
Oven Schematic
SCHEMATIC
NOTE: CONDITION OF OVEN
1. DOOR CLOSED.
HIGH VOLTAGE TRANSFORMER
MAGNETRON
H.V. RECTIFIER
TURNTABLE MOTOR
FAN MOTOR
OVEN LAMP
MONITOR SWITCH
CONTROL UNIT
2ND.
INTERLOCK
RELAY
 1ST. LATCH
 SWITCH
2ND. INTERLOCK
RELAY CONTROL
SWITCH
OL
FM
TTM
(RY-1) (RY-2)
EARTH
230 - 240V 50Hz
BLU BRN
LIVENEUTRAL G-Y
 FUSE  T6.3A
NL
NOISE SUPPRESSION COIL
NOISE FILTER  TEMP.
 FUSE
H.V. FUSE 0.6A
B1
B2
NOTE: " " indicates components with potentials above 250V
H.V. RECTIFIER
TURNTABLE MOTOR
FAN MOTOR
OVEN LAMP
CONTROL UNIT
2ND.
INTERLOCK
RELAY
OL
FM
TTM
(RY-1) (RY-2)
EARTH
BLU BRN
LIVENEUTRAL G-Y
NL
NOISE SUPPRESSION COIL
NOISE FILTER
B1
B2
HIGH VOLTAGE TRANSFORMER
MAGNETRON
MONITOR SWITCH
 1ST. LATCH
 SWITCH
2ND. INTERLOCK
RELAY CONTROL
SWITCH
230 - 240V 50Hz
 FUSE  T6.3A
 TEMP.
 FUSE
H.V. FUSE 0.6A
SCHEMATIC
NOTE: CONDITION OF OVEN
1. DOOR CLOSED.
2. COOKING TIME PROGRAMMED.
3. START BUTTON PRESSED.
Figure O-1 Oven Schematic-OFF Condition
Figure O-1 Oven Schematic-ON Condition
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