Sharp R-244(W)M User manual

R-244M - 1
SHARP CORPORATION
SERVICE MANUAL
S40189R244M//
R
MICROWAVE OVEN
MODELS
R-244(W)M
R-244(G)M
R-244(B)M
R-244(SL)M
SERVICING ............................................................................................................................................. 2
CAUTION/WARNING............................................................................................................................... 3
PRODUCT SPECIFICATIONS ................................................................................................................ 3
APPEARANCE VIEW................................................................................................................................ .4
OPERATION SEQUENCE........................................................................................................................ 5
OUTPUT POWER TEST PROCEDURE................................................................................................... 6
TEST PROCEDURES................................................................................................................................ 7
TOUCH CONTROL ASSEMBLY .............................................................................................................. 9
COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE ................................................... 13
MICROWAVE MEASUREMENT PROCEDURE...................................................................................... 16
SCHEMATIC DIAGRAMS.........................................................................................................................17
PICTORIAL DIAGRAM .......................................................................................................................... 18
CONTROL PANEL CIRCUIT ................................................................................................................. 19
SWITCH UNIT CIRCUIT DIAGRAM ....................................................................................................... 20
PRINTED WIRING BOARD OF CONTROL PANEL DIAGRAM ............................................................. 21
PRINTED WIRING BOARD OF SWITCH UNIT DIAGRAM.................................................................... 22
PARTS LIST........................................................................................................................................... 23
EXPLODED DIAGRAM OF OVEN.......................................................................................................... 26
CONTROL PANEL/DOOR PARTS ......................................................................................................... 27
PACKING AND ACCESSORIES ........................................................................................................... 28
TABLE OF CONTENTS Page
In interests of user-safety the oven should be restored to its
original condition and only parts identical to those specified
should be used.

2
R-244M -
Microwaveovenscontaincircuitrycapableofproducingveryhighvoltageandcurrent.Contactwithfollowingparts
will result in electrocution:-
High voltage capacitor, High voltage transformer, Magnetron, High voltage rectifier, High voltage wires.
REMEMBER TO CHECK 3D
1) Disconnect the supply.
2) Door opened, and wedged open.
3) Discharge high voltage capacitor.
WARNING AGAINST THE CHARGE OF THE HIGH-VOLTAGE CAPACITOR
The high-voltage capacitor remains charged about 60 seconds after the oven has been switched off. Wait for 60
secondsandthenshort-circuittheconnectionofthehigh-voltagecapacitor(thatis,oftheconnectingleadfrom the
high-voltage rectifier) against the chassis using a screwdriver with an insulated handle.
Sharp recommend that wherever possible, fault-finding is carried out with the supply disconnected. In some cases,
it may be necessary to connect the supply with the cover removed to carry out fault investigation in the control
circuitry. In such cases, the high voltage circuit should be disabled as described below to reduce the hazards:-
• Carry out 3D checks (see above).
• Disconnect the supply leads from the high voltage transformer, making a note of the polarity. Insulate the
connectors, ensuring they are positioned away from the transformer and fastened there.
• Connect any relevant test equipment e.g. voltmeter.
• Reconnect the oven to the supply, then close the door.
• Note the results of the test, taking care to keep clear of the operational oven.
• Carry out 3D checks (see above).
• Reconnect the leads to the transformer. Take care to observe correct polarity.
• Carry out 4R checks (see below).
Microwave ovens should not be used without a load. 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 microwave timer for one (1) minute, set the
powerleveltoHIGH(100%)andpushthestartkey.Whentheone(1)minutehaselapsed(timeratzero)carefullycheck
that the water is now hot.
AFTER REPAIR REMEMBER TO CHECK 4R
1) Reconnect all leads removed from components during testing.
2) Replace the outer case (cabinet).
3) Reconnect the supply.
4) Run the oven. Check all functions.
When all service work is completed, and the oven is fully assembled, the microwave power output should be checked
and microwave leakage test carried out.
IMPORTANT: Iftheovenbecomesinoperativebecauseofablown F8AFuse,checkthemonitoredlatchswitchand
monitor switch before replacing the fuse .
WARNING: WIRING / RE-WIRING
Before carrying out any work; carry out 3D checks.
1) Disconnect the supply.
2) Open the door and wedge open.
3) Discharge the high voltage capacitor.
RE-WIRING
1) Wires must not touch:
a) High voltage parts.
b) Parts that become hot.
c) Sharp edges.
d) Movable parts.
2) Positive lock connectors are fitted correctly
3) Wires are connected correctly as per pictorial diagram.
4) No wire leads are trapped by the outer wrap.
WARNING TO SERVICE PERSONNEL
SERVICING

R-244M - 3
CAUTION / WARNING
WARNING
Servicing and repair work must be carried out only by
trained service engineers.
The parts marked '*' on the parts list and schematic
diagram have voltages in excess of 250V.
Removal of the outer wrap gives access to potential
above 250V.
Allthepartsmarked"∆"onthepartslistmaycauseundue
microwave exposure, by themselves, or when they are
damaged, loosened or removed.
CAUTION
MICROWAVE RADIATION
Donotbecomeexposedtoradiationfromthemagnetron
or other parts conducting microwave energy. All input
andoutputmicrowaveconnections,waveguides,flanges
and gaskets must be secured. Never operate the
device without a microwave energy absorbing load
attached. Never look into an open waveguide or an-
tenna while the device is energized.
WARNING
THIS APPLIANCE MUST BE EARTHED. THE WIRES IN THIS MAINS LEAD ARE COLOURED IN
ACCORDANCE WITH THE FOLLOWING CODE:
GREEN-AND-YELLOW : EARTH BLUE : NEUTRAL BROWN : LIVE
If the mains lead is replaced, only part number QACCBA030WRE4 should be used
SPECIFICATION
Power Requirements 230-240 Volts 50 Hertz Single phase, 3 wire grounded
Power Consumption 1.2kW
Power Output 800W watts nominal of RF microwave energy (measured by way of IEC60705)
Operating frequency of 2450 MHz
Case Dimensions Width 449mm / Height 282mm including foot / Depth 385mm
Cooking Cavity Dimensions Width 287mm / Height 220mm / Depth 311mm
Turntable diameter 272mm
Control Complement Touch Control System
Clock(1:00-12:59 or 0:00-23:59)
Microwave Power for Variable Cooking
Repetition Rate;
HIGH .................. Full power throughout the cooking time
MEDIUM HIGH ...................... approx. 70% of Full Power
MEDIUM ................................ approx. 50% of Full Power
MEDIUM LOW....................... approx. 30% of Full Power
LOW ...................................... approx. 10% of Full Power
EXPRESS COOK button
EXPRESS DEFROST button
POWER LEVEL/WEIGHT button
STOP/CLEAR button
START/AUTO MINUTE button
Net Weight Approx. 13.3 kg
PRODUCT DESCRIPTION
As part of our policy of continuous improvement, we reserve the right to
alter design and specifications without notice

4
R-244M -
APPEARANCE VIEW
1. Door
2. Door hinges
3. Waveguide cover
4. Oven lamp
5. Control panel
6. Rubber seal
7. Door latch openings
8. Oven cavity
9. Door seals and sealing surfaces
10. Safety door latches
11. Ventilation openings
12. Outer case
13. Power supply cord
3 4
1
10
7
6
2
98
11
5
12
13
Turntable
Roller stay
Seal packing
1. Place the roller stay on the floor of the oven cavity,
engaging shaft.
2. Then place the turntable on the roller stay.
1. DIGITAL DISPLAY
2. EXPRESS COOK pad
3. EXPRESS DEFROST pad
4. TIMER Pads
5. POWER /WEIGHT STOP/CLEAR
START/AUTO MINUTE Pads
1.
2.
3.
4.
5.
OVEN

R-244M - 5
OPERATING SEQUENCE
1. Whentheovendoorisopened,theovenlampcomeson
at this time.
MICROWAVE COOKING CONDITION
2. When the cooking time is up, a single tone is heard and
the relays RY1 + RY2 go back to their home position.
The circuits to the oven lamp, power transformer, fan
motor and turntable motor are cut off.
CONNECTED COMPONENTS RELAY
Oven lamp, Fan motor, Turntable motor RY1
Power transformer RY2
CONDITION
DURING DOOR OPEN
SWITCH CONTACT COOKING (NO COOKING)
Monitor switch COM-NC Open Closed
Monitored latch switch COM-NO Closed Open
Stop switch COM-NO Closed Open
3. When the door is opened during a cook cycle, the
switches come to the following condition.
The circuits to the power transformer, fan motor and
turntablemotorarecutoffwhenthe monitored latch switch
and stop switch are made open.
Theovenlampremains on even if the ovendoor is opened
after the cooking cycle has been interrupted, because the
relayRY1staysclosed.Showninthedisplayistheremaining
time.
HIGH, MEDIUM HIGH, MEDIUM, MEDIUM
LOW, LOW COOKING
When the microwave oven is preset for variable cooking
power,thelinevoltageissuppliedtothe powertransformer
intermittently within a 32-second time base through the
relaycontactwhichiscoupledwiththecurrent-limitingrelay
(RY2). The following levels of microwave power are given.
SETTING
MEDIUM HIGH
MEDIUM LOW
Approx. 10% = 80 Watts
32 sec. ON
6 sec. ON
12 sec. ON
18 sec. ON
24 sec. ON
26 sec. OFF
20 sec. OFF
14 sec. OFF
8 sec. OFF
LOW
MEDIUM
HIGH
Approx. 70% = 560Watts
Approx. 50% = 400 Watts
Approx. 30% = 240 Watts
NOTE: TheON/OFFtimeratiodoesnotexactlycorrespond
to the percentage of microwave power, because
approx. 3 seconds are needed for heating up the
magnetron filament.
Approx. 100% = 800 Watts
OFF CONDITION DOOR OPEN MECHANISM
The door can be opened by pulling the door.
Figure D-1. Door Open Mechanism
MONITORED LATCH SWITCH AND STOP
SWITCH
1. Whentheovendoor isclosed,thecontacts(COM-NO)
must be closed.
MONITOR SWITCH
1. Whenthe oven doorisclosed,thecontacts(COM-NC)
must be opened.
2. When the oven door is opened, the contacts (COM-
NC) must be closed.
3. If the oven door is opened and he contacts (COM-NO)
of the monitored latch switch fail to open, the fuse F1
blows immediately after closing the contacts (COM-
NC) of the monitor switch.
CAUTION: BEFORE REPLACING A BLOWN FUSE F1
TEST MONITORED LATCH SWITCH (SW1)
AND MONITOR SWITCH FOR PROPER
OPERATION. (REFERTOCHAPTER“TEST
PROCEDURE”).
FUSE
1. ThefuseF1blowswhenthecontacts(COM-NO)ofthe
monitored latch switch remain closed with the oven
door open and when the contacts (COM-NC) of the
monitor switch are closed.
2. If the wire harness or electrical components are short-
circuited,thefuseF1blowstopreventanelectricshock
or fire hazard.
HVT THERMOSTAT 150˚C
Thethermostatprotectsthehighvoltagetransformeragainst
overheating.Ifthetemperaturegoesuphigherthan150˚C
because the fan motor is interrupted or the ventilation
openings are blocked, the thermostat will cycle, line volt-
age to the high voltage transformer will also cycle. (If
operated, check the magnetron for damage.)
Latch hook
SW3: Stop switch
Door
SW2: Monitor switch
SW1: Monitored latch switch
Latch heads

6
R-244M -
MICROWAVE OUTPUT POWER (IEC-60705)
The power output of this oven is rated using the method specified by IEC-60705. Full details of how to carry out this
procedure can be found in the Sharp Technical Training notes which is available from Sharp Parts Centre
(part number SERV-LITMW01).
Using this procedure, the heating time to raise 1000g of water by 10°C is approximately 50 seconds.
The IEC-60705 procedure must be carried out using laboratory-type procedures and equipment. These requirements
make the procedure unsuitable for routing performance checks. An indication of the power being produced by the oven
can however be obtained using the procedure given below.
Alternative simplified method:
1. Place 2 litres of cold water (between 12°C and 20°C) in a suitable container.
2. Stir the water and measure the temperature in °C. Note temperature as T1.
3. Place the container in the microwave and heat the water for 2 minutes on full power.
4. When the 2 minutes is completed, remove the container and stir the water. Note the water temperature as T2.
5. Calculate the output power using the following formula:
R.F. Power Output = (T2 - T1) x 70.
Note: The result from this test should be within 10% of the power rating stated on the rating label.
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 5mW/cm2), however it is not normal to detect any significant leakage,
therefore, any leakage which is detected should be investigated.
It is essential that only leakage detectors with current calibration traceable to the National Physical Laboratories are used.
Suitable leakage detectors : CELTEC A100
APOLLO X1
OUTPUT POWER TEST PROCEDURE
THERMAL CUT-OUT 125˚C (OVEN)
The thermal cut-out located on the top of the oven cavity is
designed to prevent damage to the oven, if the food 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 thermal cut-out remains closed. However,
when abnormally high temperatures are reached within the
oven cavity, the thermal cut-out will open at 125˚C, causing
theoventoshutdown.Thedefectivethermalcut-outmustbe
replaced with a new one.
TURNTABLE MOTOR
The turntable motor drives the turntable roller assembly to
rotate 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 magnetron and cools the magnetron. This air is chan-
nelledthroughtheovencavitytoremovesteamandvapours
givenofffrom heating food. It isthenexhaustedthroughthe
exhaust vents at the rear of the oven cavity.
NOISE FILTER
Thenoise filter assemblyprevents radiofrequencyinterfer-
ence that might flow back into the power circuit.
OPERATING SEQUENCE

R-244M - 7
PROCEDURE
ATOUCH CONTROL PANEL ASSEMBLY TEST
COMPONENT TEST
BTACT SWITCH TEST
1. Disconnect the oven from the power supply.
2. Discharge the high voltage capacitor.
3. Remove the control unit from the control panel.
4. By using an ohmmeter, check the tact switch operation.
5. When the tact switch is not depressed, an ohmmeter should indicate an open circuit. When the tact
switch is depressed, an ohmmeter should indicate a short circuit. If improper operation is indicated,
the tact switch is probably defective and should be checked.
CRELAY TEST
Do not touch the electrical parts and the printed wiring board to prevent an electric
CAUTION shock. Because the control unit is " TRANSLESS CIRCUIT " and all electrical parts
are used at A.C. line voltage.
ThetouchcontrolpanelconsistsofcircuitsincludingsemiconductorssuchasLSI,ICs,etc.Therefore,
unlikeconventionalmicrowaveovens,propermaintenancecannotbeperformedwithonlyavoltmeter
and ohmmeter.
In this service manual, the touch control panel assembly is divided into two units, Control Unit and
Switch Unit, and troubleshooting by unit replacement is described according to the symptoms
indicated.
1. Switch Unit. Note : Check switch unit lead wire harness connection before replacement.
The following symptoms indicate a defective switch unit. Replace the switch unit.
a) When touching the keys, a certain key produces no signal at all.
b) When touching a key, two figures or more are displayed.
c) When touching the keys, sometimes a key produces no signal.
2. Control Unit
The following symptoms indicate a defective control unit. Before replacing the control unit
perform the Switch unit test (Procedure M) to determine if control unit is faulty.
2-1 In connection with keys.
a) When touching the keys, a certain group of keys do not produce a signal.
b) When touching the keys, no keys produce a signal.
2-2 In connection with indicators
a) At a certain digit, all or some dots do not light up.
b) At a certain digit, brightness is low.
c) Only one indicator does not light.
d) The corresponding dots of all digits do not light up; or they continue to light up.
e) Wrong figure appears.
f) A certain group of indicators do not light up.
g) The figure of all digits flicker.
2-3 Other possible problems 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.
TEST PROCEDURES
LETTER
Remove the outer case and check voltage between Pin No 5 of the 3 pin connector (A) and common
terminal of the relay (RY2) on the control unit with an A.C. voltmeter.
The meter should indicate rated voltage, 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.......Checkdiodewhichisconnectedtotherelaycoil.Ifdiodeisgood,control
unit is defective.
RELAY SYMBOL OPERATIONAL VOLTAGE CONNECTED COMPONENTS
RY1 Approx. 18.0V D.C. Oven lamp / Turntable motor / Cooling fan motor
RY2 Approx. 7.0V D.C. High voltage transformer

8
R-244M -
PROCEDURE
LETTER COMPONENT TEST
EPROCEDURES TO BE TAKEN WHEN THE FOIL PATTERN ON THE PRINTED WIRING BOARD
(PWB) IS OPEN
TEST PROCEDURES
To protect the electronic circuits, this model is provided with a fine foil pattern added to the input circuit 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.
STEPS OCCURRENCE CAUSE OR CORRECTION
1 The rated voltage is not applied between Pin Check supply voltage and oven power cord.
No. 5 of the 3 pin connector (A) and the
common terminal of the relay RY2.
2 Only pattern at "a" is broken. *Insert jumper wire J1 and solder.
3 Pattern at "a" and "b" are broken. *Insert the coil RCILF2003YAZZ between "c" and "d".
NOTE: *At the time of making these repairs,
makeavisualinspectionofthevaristor.
Check for burned damage. If any ab-
normal condition is detected, replace
the defective parts.
(J1)
b
c d
a
51
R70
RY2
R1
D71
VRS1
ZD70
RY1
DSWITCH UNIT TEST
Ifthe displayfails toclear whentheSTOP/CLEAR
key is depressed, first verify the lead wire harness
is making good contact, verify that the stop switch
operates properly; that is the contacts are closed
whenthedoorisclosedandopenwhenthedooris
open. If the stop switch is good, disconnect the
lead wire harness that connects the switch unit to
the display unit and make sure the stop switch is
closed (either close the door or short the stop
switch connector). Use the Switch unit matrix indi-
cated on the switch unit circuit and place a jumper
wire between the pins that correspond to the
STOP/CLEAR key making momentary contact. If
the display unit responds by clearing with a beep
theswitchunitisfaultyandmustbereplaced.Ifthe
displayunitdoesnotrespond,itisafaultyandmust
bereplaced.Ifaspecifickeydoesnotrespond,the
above method may be used (after clearing the
display unit) to determine if the display unit or
switch unit is at fault.
1
2
3
4
SW4
5
6
SW5
SW6
SW7
10
sec.
10
min.
1
min.
COOK
DEFROST
STOP
CLEAR
SW8
SW1
CN - C
CN - C
6Pin HARNESS
SW2
SW3
POWER
WEIGHT
START
AUTO MINUTE

R-244M - 9
TOUCH CONTROL PANEL ASSEMBLY
OUTLINE OF TOUCH CONTROL PANEL
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 (tact switch touch sound and completion
sound).
6) Synchronizing Signal Circuit
The power source synchronizing signal is available in
ordertocomposeabasicstandardtimeintheclockcircuit.
It accompanies a very small error because it works on
commercial frequency.
7) Door Sensing Switch (Stop 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
LED1-LED3)
The touch control section consists of the following units.
(1) Switch Unit
(2) Control Unit
The principal functions of these units and the signals
communicated among them are explained below.
Switch Unit
Theswitchunitiscomposedofamatrix,signalsgenerated
intheLSIaresenttotheswitchunitthroughR60,R61,R62
and R63.
When a switch button is touched, a signal is completed
throughtheswitchunitandpassedbacktotheLSIthrough
R81 and R83 to perform the function that was requested.
Control Unit
Control unit consists of LSI, ACL circuit, indicator circuit,
powersource circuit, relaycircuit, buzzercircuit, synchroniz-
ing signal circuit and back light circuit.
1) ACL
Thiscircuit generatesasignal which resetsthe LSI tothe
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
Thiscircuitgeneratesvoltagenecessaryinthecontrolunit
from the AC line voltage.
Symbol Voltage Application
VC +5V LSI(IC1)

10
R-244M -
HIGH
H : +5V
L : 0V
H : +5V
L : 0V
MEDIUM
HIGH
ON
ON
OFF
OFF OFF
24 sec.
8 sec.
A
B
0.1 sec.
2 sec.
H : +5V
L: 0V
H : +5V
L: 0V
20.0 msec
During cooking
H : +5V
L : 0V
20.0 msec
H : +5V
L : 0V
1-12 SEG0 - OUT Segment data signal.
SEG11 Connected to LCD.
The relation between signals are as follows:
LSI signal (Pin No.) LCD (Pin No.) LSI signal (Pin No.) LCD (Pin No.)
SEG 0 (1) ................................ S6 SEG 6 (7)........................... S12
SEG 1 (2) ................................ S7 SEG 7 (8)............................. S5
SEG 2 (3) ................................ S8 SEG 8 (9)............................. S4
SEG 3 (4) ................................ S9 SEG 9 (10)........................... S3
SEG 4 (5) .............................. S10 SEG 10 (11)......................... S2
SEG 5 (6) .............................. S11 SEG 11 (12)......................... S1
13 R60 OUT Tact switch strobe signal.
Signalappliedto tactswitchsection.A pulsesignalisinput toR81or R83 terminal
while the tact switch SW1 or SW8 is touched.
14 R61 OUT Tact switch strobe signal.
Signal applied to tact switch section. A pulse signal is input to R81or R83 terminal
while the tact switch SW2 or SW5 is touched.
15 R62 OUT Tact switch strobe signal.
Signalappliedto tactswitchsection.A pulsesignalisinput toR81or R83 terminal
while the tact switch SW3 or SW6 is touched.
16 R63 OUT Tact switch strobe signal.
Signalappliedto tactswitchsection.A pulsesignalisinput toR81or R83 terminal
while the tact switch SW4 or SW7 is touched.
17 AIN0 IN Toinputsignalwhichcommunicatesthedooropen/closeinformationtoLSI.
Door close "L" level signal (0V). Door open "H" level (+5V)
18-20 AIN1-AIN3 IN Terminal to change functions according to the Model.
ByusingtheA/DconvertercontainedintheLSI,DCvoltageinaccordancewiththe
Model in operation is applied to set up its function.
21 VSS IN Power source voltage: 0V.
VSS voltage of power source circuit input.
22 R70 OUT Magnetron high-voltage circuit driving signal.
To turn on and off the cook relay
(RY2). The signals holds "L" level
during microwave cooking and "H"
levelwhilenotcooking.Inothercook-
ingmodes(variablecooking)thesig-
nal turns to "H" level and "L" level in
repetitionaccordingtothepowerlevel.
23 R71 OUT Signal to sound buzzer (2.0 kHz).
A: Tact switch touch sound.
B: Completion sound.
24 R72 OUT Oven lamp, fan motor and turntable motor driving signal.
Toturnonandoffshutoffrelay(RY1).The
square waveform voltage is delivered to
the RY1 driving circuit.
25 R73 IN Terminal not used.
26 INT2 IN Signal synchronized with commercial power source frequency.
This is the basic timing for time processing of LSI.
DESCRIPTION OF LSI
LSI(IXA085DR)
The I/O signal of the LSI(IXA085DR) are detailed in the following table.
Pin No. Signal I/O Description