Sharp R-211A User manual

R-211A
TABLE OF CONTENTS Page
CAUTION, MICROWAVE RADIATION .............................................................................................................. 1
WARNING............................................................................................................................................................1
PRODUCT SPECIFICATIONS........................................................................................................................... 2
GENERAL INFORMATION ................................................................................................................................. 2
APPEARANCE VIEW......................................................................................................................................... 3
OPERATION SEQUENCE ................................................................................................................................. 4
FUNCTION OF IMPORTANT COMPONENTS ................................................................................................... 5
SERVICING ........................................................................................................................................................ 6
TEST PROCEDURE .......................................................................................................................................... 8
COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE............................................................. 13
MICROWAVE MEASUREMENT ...................................................................................................................... 19
WIRING DIAGRAM .......................................................................................................................................... 20
PICTORIAL DIAGRAM..................................................................................................................................... 21
PARTS LIST...................................................................................................................................................... 22
In interests of user-safety the oven should be restored to its original
condition and only parts identical to those specified should be used.
MODEL R-211A
S5709R211APX/
MICROWAVE OVEN
SHARP CORPORATION
SERVICE MANUAL
OPEN DOOR
COOKING CONTROL
TIMER
0
5
20
25 10
15
0.5 kg
30
1 kg

DEFROST (Kg)
M
E
D
D
E
F
R
O
S
H
I
G
H

R-211A

R-211A
1
SERVICE MANUAL
SHARP CORPORATION
OSAKA, JAPAN
MICROWAVE OVEN
R-211A
GENERAL IMPORTANT INFORMATION
ThisManualhasbeenpreparedtoprovideSharpCorp.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 qualified to render
satisfactory customer service.
CAUTION
MICROWAVE RADIATION
DO NOT BECOME EXPOSED TO RADIATION FROM
THE MICROWAVE GENERATOR OR OTHER PARTS
CONDUCTING MICROWAVE ENERGY.
Serviceengineersshouldnotbeexposedtothemicrowave
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, flanges 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.
Allthepartsmarked"★"onpartslistareusedatvoltagesmore
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 dam-
aged, loosened or removed.
TEST PROCEDURE
SERVICING AND
TROUBLESHOOTING CHART
FUNCTION OF IMPORTANT
COMPONENTS
OPERATING SEQUENCE
APPEARANCE VIEW
WIRING DIAGRAM
PARTS LIST
COMPONENT REPLACEMENT
AND ADJUSTMENT PROCEDURE
MICROWAVE MEASUREMENT
PRODUCT SPECIFICATIONS

2
R-211A
PRODUCT DESCRIPTION
SPECIFICATION
ITEM DESCRIPTION
Power Requirements 220 Volts
50 Hertz
Single phase, 3 wire earthed
Power Consumption 1.06 KW
Power Output 700 watts nominal of RF microwave energy (IEC-705-1988)
Operating fequency 2450 MHz
Case Dimensions Width 450 mm
Height 295 mm including foot
Depth 357 mm
Cooking Cavity Dimensions Width 285 mm
Height 178 mm
Depth 316 mm
Turntable diameter 272mm
Control Complement 30 min. Single Speed Timer.
Microwave Power for Variable Cooking
Repetition Rate;
HIGH .................................. Full power throughout the cooking time
MEDIUM / DEFROST......................... approx. 45% of FULL Power
Set Weight (Approx.) Approx. 14 kg
GENERAL INFORMATION
WARNING
THIS APPLIANCE MUST BE EARTHED
IMPORTANT
THE WIRES IN THIS MAINS LEAD ARE COLOURED IN ACCORDANCE WITH THE FOLLOWING CODE:
GREEN-AND-YELLOW : EARTH
BLUE : NEUTRAL
BROWN : LIVE

R-211A
3
APPEARANCE VIEW
OVEN
6. Coupling
7. Control panel
8. Door lock openings
9. Ventilation openings
1. Power supply cord
2. Oven lamp
3. Door hinges
4. Safety door latches
5. Door
32
456
7
8
19
COOKING CONTROL
TIMER
OPEN DOOR
0
5
20
25 10
15
0.5kg
30
1kg


DEFROST(Kg)
M
E
D
D
E
F
R
O
S
H
I
G
H
VARIABLE COOKING CONTROL
There are power levels. The approximate
percentage of microwave power for each 
setting is:

HIGH 100%
MEDIUM/DEFROST 45%
TIMER (0 - 30 min.)
Turn to set cooking time.
DOOR OPEN BUTTON
COOKING CONTROL
TIMER
OPEN DOOR
0
5
20
25 10
15
0.5 kg
30
1 kg


DEFROST (Kg)
M
E
D
D
E
F
R
O
S
T
H
I
G
H
MEAT DEFROST GUIDE
(Inner scale)
CONTROLPANEL

4
R-211A
OPERATION SEQUENCE
cycle of a cooking program, the 1st latch switch and
2ndlatchswitchmustopentheir(COM-NO)contacts
first. After that the contacts (COM-NC) of the monitor
switch can be closed.
7-2. When the oven door is closed. The contacts (COM-
NC) of the monitor switch must be opened and the
contacts (COM-NO) of the 2nd latch switch and the
1st latch switch must be closed.
7-3. When the oven door is opened and the (COM-NO)
contacts of the 1st latch switch and the contacts
(COM-NO)ofthe2nd latch switch remain closed,the
fuseM6.3Awillblow,themonitorswitchisclosedand
a short circuit is caused.
HIGH, MEDIUM / DEFROST COOKING
When the microwave oven is preset for variable cooking
power, the rated voltage is supplied to the power trans-
formerintermittentlywithina30-secondtimebasethrough
the vari switch. The following levels of microwave power
are given.
SETTING
HIGH Approx. 100%
Approx. 45%
30 sec. ON
MEDIUM DEFROST
13.5 sec. ON 16.5 sec. OFF
Note: The ON/OFF time ratio does not exactly corre-
spond to the percentage of microwave power,
because approx. 2 seconds are needed for heat-
ing up the magnetron filament.
OFF CONDITION
1. When the timer knob is at " 0 ", the oven is OFF
condition.
2. Closingtheovendooractivatesthe1stlatchswitch,the
2nd latch switch and monitor switch.
IMPORTANT:
When the oven door is closed, the contacts COM-NC of
the monitor switch must be open.
Figure O-1 on page 20
MICROWAVE COOKING CONDITION
HIGH COOKING
Set the variable cooking control to HIGH and then set the
timer.
Function sequence
Figure O-2 on page 20
1. Following components are energized.
Power transformer H.V. capacitor Timer motor
Magnetron H.V. rectifier Fan motor
Turntable motor Oven lamp
2. Ratedvoltage issuppliedto the primarywindingof the
power transformer. The voltage is converted to about
3.3 volts A.C. output on the filament winding and high
voltage of approximately 2000 volts A.C. on the sec-
ondary winding.
3. The filament winding voltage (3.3 volts) heats the
magnetronfilamentandthehighvoltage(2000volts)is
sent to the voltagedoubling circuit, where it is doubled
to negative voltage of approximately 4000 volts D.C..
4. The 2450 MHz microwave energy produced in the
magnetron generates a wave length of 12.24 cm. This
energyischannelledthroughthewaveguide(transport
channel)intothe oven cavity,wherethefoodisplaced
to be cooked.
5. When the cooking time is up, the timer returns to "0",
thebellringsandthe contacts of the timer areopened.
Then following components are turned off.
Power transformer Magnetron Timer motor
Turntable motor H.V. capacitor Fan motor
H.V. rectifier Oven lamp
6. Whentheoven door isopenedduringacookingcycle,
the switches come to the following positions and they
are common to the other cooking conditions too.
Switch Contact Condition
During Oven Door
Cooking Open(No cooking)
1st latch Switch COM-NO Closed Opened
Monitor Switch COM-NC Opened Closed
2nd latch switch COM-NO Closed Opened
The circuit to the power transformer, turntable motor,
timer motor, fan motor and oven lamp are cut off when
the COM-NO contacts of the 2nd latch switch and 1st
latchswitcharemadeopen.Thetimerstopstoindicate
how much cooking time remains.
7. MONITOR SWITCH CIRCUIT
The monitor switch is mechanically controlled by the
oven door, and monitors the operation of the 1st latch
switch and 2nd latch switch.
7-1. When the oven door is opened during or after the

R-211A
5
FUNCTION OF IMPORTANT COMPONENTS
DOOR OPEN MECHANISM
The door is opened by pushing the open button on the
control panel, refer to the Figure D-1.
When the open button is pushed, the open button pushes
theswitchleverupandinturnthelatchheadsarereleased
from latch hook. When the latch heads are released, the
switch lever returns to its original position by its own
weight.
LATCH HOOK
LATCH
HEADS
DOOR
MONITOR SWITCH
1 ST. LATCH
SWITCH
SWITCH LEVER
2ND. LATCH
SWITCH
Figure D-1. Door Open Mechanism
1ST.LATCH SWITCH AND2ND.LATCHSWITCH
1. Whentheovendoorisclosed,thecontacts(COM-NO)
must be closed.
2. When the oven door is opened, the contacts (COM-
NO) must be opened.
MONITOR SWITCH
1. Whentheovendoorisclosed,thecontacts(COM-NC)
must be opened.
2. When the oven door is opened, the contacts (COM-
NC) must be closed.
3. Iftheovendoorisopenedandthecontacts(COM-NO)
ofthe1stlatchswitchand 2nd latchswitchfailtoopen,
the fuse blows simultaneously with closing the con-
tacts (COM-NC) of the monitor switch.
CAUTION: BEFORE REPLACING A FUSE F TEST
THE1STLATCHSWITCHSW1,2NDLATCH
SWITCH, MONITOR SWITCH AND MONI-
TORRESISTOR R FORPROPEROPERA-
TION. (REFER TO CHAPTER "TEST PRO-
CEDURE".)
MONITOR RESISTOR 0.8Ω20W
The monitor resistor prevents the fuse F bursting when
the fuse blows due to the operation of the monitor
switch.
FUSE
1. Thefuseblowswhenthecontacts(COM-NO)ofthe1st
latch switch and 2nd latch switch remain closed with
the oven door open and when the monitor switch
closes.
2. If the wire harness or electrical components are short-
circuited,thefuseblowstopreventanelectricshockof
fire hazard.
TEMPEATURE FUSE 120˚C (OVEN)
The temp. fuse located on the top of the oven cavity is
designedtopreventdamage totheovenifthefoodsinthe
oven catch fire due to over heating produced by improper
settingofcooktimeorfailure of controlunit.Undernormal
operation,thetemp.fuseremainsclosed.However,when
abnormally high temperatures are reached within the
ovencavity,thetemp.fusewillopenat120˚C,causingthe
oven to shut down. The defective fuse must be replaced
with a new one.
THERMAL CUT-OUT 95˚C (MAGNETRON )
The thermal cut-out located on the top of the oven cavity
isdesignedtopreventdamagetothemagnetronifanover
heated condition develops in the tube due to cooling fan
failure,obstructedairguide,dirtyorblockedairintake,etc.
Under normal operation, the thermal cut-out remains
closed.However,whenabnormallyhightemperaturesare
reached within the magnetron, the thermal cut-out will
open at 95˚C, causing the oven to shut down. When the
magnetron has cooled to 75˚, the thermal cut-out closes
and cook cycle will resume.
TURNTABLE MOTOR
The turntable motor drives the roller stay to rotate the
turntable.
FAN MOTOR
Thefanmotordrivesabladewhichdrawsexternalcoolair.
Thiscool air isdirectedthroughthe air vanessurrounding
the magnetron and cools the magnetron. This air is chan-
nelled through the oven cavity to remove steam and
vapours given off from the heating foods. It is then ex-
hausted through the exhausting air vents at the oven
cavity.
TIMER MOTOR (WITH VARI-SWITCH)
Timer switch
1. Whenthetimerisat"0"position,theswitchofthetimer
are opened.
2. When the timer is turned clockwise from "0" position,
the switch of the timer are closed.
Vari-switch
If the variable cooking control is set at HIGH or ME-
DIUM DEFROST, cooking position, Rated voltage is
supplied to the power transformer intermittently within
a 30 seconds time base. The following chart shows the
vari-switch operation in the various modes.
are given.
SETTING
HIGH Approx. 100%
Approx. 45%
30 sec. ON
MEDIUM DEFROST
13.5 sec. ON 16.5 sec. OFF
Note: The ON/OFF time ratio does not exactly corre-
spond to the percentage of microwave power,
because approx. 2 seconds are needed for heat-
ing up the magnetron filament.

6
R-211A
SERVICING
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.
Microwave ovens should not be run empty. To test for
thepresenceofmicrowaveenergywithinacavity,place
acupofcoldwaterontheoventurntable,closethedoor
andsetthepowerleveltoHIGH.Andsetthemicrowave
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 remains cold carry out 3D checks
and re-examine the connections to the component
being tested.
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
switchedoff.Waitfor60secondsandthenshort-
circuittheconnectionofthehigh-voltagecapaci-
tor (that is, of the connecting lead of the high-
voltagerectifier)againstthechassiswiththeuse
of an insulated screwdriver.
Sharp recommend that wherever possible fault-finding
is carried out with the supply disconnected. It may in,
some cases, be necessary to connect the supply after
theoutercasehasbeenremoved,inthiseventcarryout
3Dchecksandthendisconnecttheleadstotheprimary
of the power transformer. Ensure that these leads
remain isolated from other components and the oven
chassis. (Use insulation tape if necessary.) When the
testingiscompletedcarryout3Dchecksandreconnect
the leads to the primary of the power transformer.
Whenallserviceworkiscompleted,andtheovenisfullyassembled,themicrowavepoweroutputshouldbechecked
and microwave leakage test carried out.
When troubleshooting the microwave oven, it is helpful to
follow the Sequence of Operation in performing the
checks.Manyofthepossiblecausesoftroublewillrequire
that a specific test be performed. These tests are given a
procedureletterwhichwillbefoundinthe"TestProcedure
"section.
TROUBLESHOOTING GUIDE
IMPORTANT: If the oven becomes inoperative because
of a blown fuse M6.3A in the 1st. latch
switch - 2nd. latch switch - monitor switch
- monitor resistor circuit, check the 1st.
latch switch, 2nd. latch switch, monitor
switchand monitorresistorbeforereplac-
ing the fuse M6.3A.
WARNINGTO SERVICE PERSONNEL
Microwaveovenscontaincircuitrycapableofproducingveryhighvoltageandcurrent.Contactwithfollowingparts
will result in electrocution.
High voltage capacitor, Power transformer, Magnetron, High voltage rectifier assembly, High voltage harness.

R-211A
7
TROUBLESHOOTING CHART
PROBLEM
Fuse M6.3Ablowswhenpower
cord is plugged into wall outlet.
Fuse M6.3A blows when
the door is opened.
Home fuse blows when
power cord is plugged into
wall outlet.
Ovendoesnotoperateatall.
Oven goes into cook cycle
butshutsdownbeforeendof
cooking cycle.
Oven lamp does not light.
(Fan motor rotates)
Fanmotordoesnotoperate,
but oven lamp lights.
Timer motor does not oper-
ate, but oven lamp lights.
Turntablemotordoesnotop-
erate, but oven lamp lights.
Ovenseemstobeoperating
but little or no heat is pro-
duced in oven load. (Micro-
wave power control is set at
"HIGH" position, and turnta-
ble motor operates.)
Ovendoesnotoperateprop-
erly in another position ex-
cept "HIGH" position.
POSSIBLE CAUSE
AND
DEFECTIVE PARTS
TEST PROCEDURE
OFF
CONDITION
CONDITION
MAGNETRON POWER TRANSFORMER H.V. RECTIFIER ASSEMBLY HIGH VOLTAGE CAPACITOR 1ST. LATCH SWITCH
2ND. LATCH SWITCH MONITOR SWITCH TEMPERATURE FUSE 120˚C (OVEN) THERMAL CUT-OUT 95˚C (MG) TIMER MOTOR
TIMER CONTACT TIMER DEFROST SWITCH FAN MOTOR TURNTABLE MOTOR FUSE M6.3A
POWER SUPPLY CORD SHORTED WIRE HARNESS OPENED WIRE HARNESS OVEN LAMP OR SOCKET BLOCKED VENTILATION OPENING
MISADJUSTMENT SWITCH HOME FUSE OR BREAKER WALL OUTLET BLOCKED COOLING FAN
POWER SELECT SWITCH
ABCDEEEGGJ J JHH I E
COOKING
CONDITION

8
R-211A
CARRY OUT 3D CHECKS.
Isolate the magnetron from the high voltage circuit by removing all leads connected to the filament
terminal.
Totestforanopencircuitfilamentuseanohmmetertomakeacontinuitytestbetweenthemagnetron
filament terminals, the meter should show a reading of less than 1 ohm.
Totestfora short circuit filament toanodecondition,connectohmmeterbetweenoneofthefilament
terminalsandthecaseofthemagnetron(ground).Thistestshouldbeindicatedaninfiniteresistance.
If a low or zero resistance reading is obtained then the magnetron should be replaced.
MICROWAVE OUTPUT POWER (IEC705)
The following test procedure should be carried out with the microwave oven in a fully assembled
condition (outer case fitted). Microwave output power from the magnetron can be measured by way
of IEC 705, i.e. it can be measured by using water load how much it can be absorbed by the water
load.Tomeasurethemicrowaveoutputpowerinthemicrowaveoven,therelationofcalorieandwatt
is used. When P(W) heating works for t(second), approximately P x t/4.187 calorie is generated. On
theotherhand,ifthe temperature of the water withV(ml)rises∆T(˚C)duringthismicrowaveheating
period, the calorie of the water is V x ∆T.
Measuring condition:
1. Container
The water container must be a cylindrical borosilicate glass vessel having a maximum material
thickness of 3 mm and an outside diameter of approximately 190 mm.
2. Temperature of the oven and vessel
The oven and the empty vessel are at ambient temperature prior to the start of the test.
3. Temperature of the water
The initial temperature of the water is (10±2)˚C.
4. Select the initial and final water temperature so that the maximum difference between the final
water temperature and the ambient temperature is 5˚C.
5. Selectstirringdevicesandmeasuringinstrumentsinordertominimizeadditionorremovalofheat.
6. The graduation of the thermometer must be scaled by 0.1˚C at minimum and an accurate
thermometer.
7. The water load must be (1000±5) g.
8. “t”ismeasuredwhilethemicrowavegeneratorisoperatingatfullpower.Magnetronfilamentheat-
up time is not included.
NOTE: The operation time of the microwave oven is “t + 2” sec. 2 sec. is magnetron filament heat-
up time.
Measuring method:
1. Measure the initial temperature of the water before the water is added to the vessel.
(Example: The initial temperature T1 = 11˚C)
2. Add the 1 litre water to the vessel.
3. Place the load on the centre of the shelf.
4. Operate the microwave oven at HIGH for the temperature of the water rises by a value ∆T of
(10 ±2)˚C.
5. Stir the water to equalize temperature throughout the vessel.
6. Measure the final water temperature. (Example: The final temperature T2 = 21°C)
7. Calculate the microwave power output P in watts from above formula.
NEVERTOUCHANYPARTINTHECIRCUITWITHYOURHANDORANINSULATEDTOOL
WHILE THE OVEN IS IN OPERATION.
The formula is as follows;
P x t / 4.187 = V x ∆T P (W) = 4.187 x V x ∆T / t
Our condition for water load is as follows:
Room temperature..............around 20˚C Power supply Voltage.........Rated voltage
Water load.........1000 g Initial temperature...........10±2°C Heating time.........60 sec.
P = 70 x ∆T
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
A MAGNETRON TEST