Sharp R-3A53 User manual

R-3A53
R-3A53B
SHARP SERVICE MANUAL
S7105R3A53PJZ
_1-1- --.II__ .----- -_ __ _ I. .^ II
MICROWAVE OVEN
MODELS R-3A53
Photo R-3A53 R-3A53B ’
In interests of user-safety the oven should be restored to its original
condition and only manufacturer original spare parts must be used.
TABLE OF CONTENTS Page
GENERAL IMPORTANT INFORMATION ...................................................................................................... 1
CAUTION, MICROWAVE RADIATION,WARNING ...................................................................................... 1
PRODUCT SPECIFICATIONS ......................................................................................................................... 2
APPEARANCE VIEW ........................................................................................................................................ 3
OPERATION SEQUENCE ................................................................................................................................. 4
FUNCTION OF IMPORTANT COMPONENTS .............................................................................................. 5
SERVICING ........................................................................................................................................................ 7
TEST PROCEDURE ........................................................................................................................................ 10
TOUCH CONTROL ASSEMBLY .................................................................................................................. 19
COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE ..................................................... 25
MICROWAVE MEASUREMENT ................................................................................................................... 33
TEST DATA AT A GLANCE .............................................................................. :-.
.......................................... 34
WIRING DIAGRAM ....................................................................................................................................... 35 .
PICTORIAL DIAGRAM .................................................................................................................................. 37
CONTROL PANEL CIRCUIT ......................................................................................................................... 39
PRINTED WIRING DIAGRAM ..................................................................................................................... 40
PARTS LIST .................................................................................................................................................... 41
PACKING AND ACCESSORIES ................................................................................................................... 46
SHARP CORPORATION

SERVICE MANUAL
SHARI=
MICROWAVE OVEN
R-3A53/ R-3A53B
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 qualified to render
satisfactory customer service.
-. ___-
CAUTION
MICROWAVE RADIATION
Service engineers should not be exposed to the micro-
wave 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,
All the parts marked ,,*‘I on parts list are used at voltages
more than 250V.
SHARP CORPORATION
OSAKA, JAPAN
R-3A53
R-3A53B
/ . -.
PRODUCT SPECIFICATIONS
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R -3A53
R-3A53B
PRODUCT SPECIFICATIONS
SPECIFICATION
ITEM
Power Requirements
!
I DESCRIPTION
1 240 Volts : Australia 230- 240 Volts : New Zealand
50 Hertz
Power Consumption
I_--------
Power Output
_____---
Outside Dimensions
Single phase, 3 wire earthed
---I 1.I 6kW Awox. 5.0 A,
/ 700W (IEC-705-1988),‘6OOW (2 litre water load)
1 Operating frequency of 2450MHz
, Width 450mm
1 Height 285mm
) --Depth 340mm
Cooking Cavity Dimensions / Width 285 mm
i Height 185 mm
~-__-____---- i Depth 313mm
Turntable diameter I 272mm
--____ I
Control Complement / Touch Control System
/ Clock! I:00 - 12:59 )
Timer (0 - 99 minutes 99 seconds )
, Microwave Power for Variable Cooking
Repetition Rate;
HIGH ................................. Full power throughout the cooking time
MEDIUM HIGH ,.***...............*.*................ approx. 70% of Full Power
MEDIUM ......t........................................... approx. 50% of Full Power
MEDIUM LOW ........................................ approx. 30% of Full Power
LOW .,...*....*..*,..........,..........................,..... approx. 10% of Full Power
AUTO COOK
--~
Set Weight
1 EASY REHEAT
’ EASY DEFROST
1 INSTANT COOK/START
j MEMORY
’ AUTO START/CLOCK
VARIABLE COOKING CONTROL
INSTANT ACTION (4 menu)
NUMBER
STOP/CLEAR
Approx. 14.0 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-3A53
R -3A53B
APPEARANCE VIEW
v 0
6 0.6
1. Ventilation openings 8. Door buttonopen
2. Oven lamp 9. Touch Control Panel
3. Waveguide cover 10. Digital readout
4. Hinges 11. Access cover for oven lamp replacement
5. Safety door latches 12. Power supply cord
6. See through door 13. Roller Stay
7. Hole of oven cavity 14. Turntable
*Place the-roller stay on
the hole of oven cavity in
the oven and seat the
turntable on the roller
stay.
Touch Control Panel I 2 SERVE QUANTITY PAD
INSTANT ACTION PADS
Touch once to cook or reheat
4 popular menu.
AUTO COOK
mode.
AUTO COOK MEN&
NUMBER PADS
clock time, weight or quantity
of food, or to select the Auto
Cook menus.
MEMORY
Touch to enter one frequently
used cooking programme.
Touch to recall the memorized
programme.
VARIABLE COOKING
CONTROL PADS
Touch to select microwave
power setting.
If not touched, HIGH is auto-
matically selected.
STOP/CLEAR PAD
Touch to erase
gramming.
Touch once to stop operation
of oven during cooking; touch
twice to cancel cooking pro-
gramme.
I
I
- INSTANT ACTION -
AUTO START/CLOCK PAD
Touch to set clock or Auto
Start time.
To cook two serves, touch this
pad prior to touching the
INSTANT ACTION pad.
- 3 SERVE QUANTITY PAD
To cook three serves, touch this
pad prior to touching the
INSTANT ACTION pad.
r
4 SERVE QUANTITY PAD
To cook four serves, touch this
pad prior to touching the
INSTANT ACTION Pad.
- EASY DEFROST PAD
Touch to defrost meat by
entering weight.
MORE( A 1, LESS( v 1PADS
Touch to increase/decrease
the time in one minute incre-
ments during cooking or to
increase/decrease the time
whilst programming the Auto
Cook, INSTANT ACTION or
Easy Defrost modes.
-J
.INSTANT COOK/START PAD
Touch once to cook for 1
minute at HIGH or increase by
1 minute multiples each time
this pad is touched during
cooking.
Touch to start oven after
setting programmes.
3

I?-3A53
R-3A530
OPERATING SEQUENCE
OFF CONDITION 3.
Closing the door activates all door interlock switches
(1 st latch switch, 2nd latch switch and stop 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 voltage (240 Volts : Australia, 230- 240 Volts :
New Zealand) is supplied to the point Al + A3 in the
control unit.
4
5
1.
2.
3.
Figure O-l on page 33 (For Australian)
Figure O-3 on page 34 (For Ney Zealand)
The display flashes “88:88”.
To set any programmes or set the clock, you must
first touch the STOP/CLEAR key.
91 .
. ” appears in the display and the time counts
up every minute.
NOTE: When the oven door is opened, the oven
lamp comes on at this time.
MICROWAVE COOKING CONDITION
HIGH COOKING
Enter a desired cooking time with the touching
NUMBER key and start the oven with touching
START key.
Function sequence
Figure O-2 on page 33 (For Australian)
Figure O-4 on page 34 (For New Zealand)
CONNECTED COMPONENTS RELAY
Oven lamp, Fan motor, Turntable motor
--
Power transformer
RYI
RY2 -
1. Rated voltage is supplied to the primary winding of
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 secondary winding.
2. The filament winding voltage (3.3 volts) heats the
magnetron filament and the high voltage (2000
volts) is sent to the voltage doubling circuit, where
it is doubled to negative voltage of approximately
4000 volts D.C..
6.
The 2450 MHz microwave energy produced in the
magnetron generates a wave length of 12.24 cm.
This energy is channeled 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 relays RYI + RY2 go back to their home
position. The circuits to the oven lamp, power
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.
CONDITION
DURING DOOR OPEN
SWITCH CONTACT COOKING (NO COOKING)
1st latch switch COM- NO Closed Open
Monitor switch COM- NC Open Closed
2nd latch switch COM - NO Closed Open
Stop switch COM- NO Closed Open
The circuits to the power transformer, fan motor and
turntable motor are cut off when the 1st latch
switch, 2nd latch switch and stop switch are made
open.
The oven lamp remains on even if the oven door is
opened after the cooking cycle has been inter-
rupted, because the relay RYI stays closed. Shown
in the display is the remaining time.
MONITOR SWITCH CIRCUIT
The monitor switch is mechanically controlled by
oven door, and monitors the operation of the 1st
and 2nd latch switches.
6-1 When the oven door is opened during or after the
cycle of a cooking program, the 1st latch and 2nd
latch switches must open their contacts first. Af-
ter that the contacts (COM - NC) of the monitor
switch can be closed and then contacts of the
stop switch can be opened.
6-2. When the oven door is closed, the contacts
(COM - NC) of the monitor switch must be
opened and the contacts (COM - NO) of the stop
switch must be closed first. After that the con-
tacts of the 1st latch switch and 2nd latch
switches are closed.
6-3. When the oven door is opened and the contacts
of the 1st and 2nd latch switches remain closed.
The fuse M6.3A will blow, because the monitor
switch is closed and a short circuit is caused.

R -3A53
R-3A53B
MEDIUM HIGH, MEDIUM, MEDIUM LOW,
LOW COOKING
When the microwave oven is preset for variable cook-
ing power, 240 volts A.C. power is supplied to the
power transformer intermittently within a 32-second
time base through the relay contact which is coupled
with the current-limiting relay, The following levels of
microwave power are given.
SETTING
32 set ON
HIGH
24 set ON 8 set OFF
MEDIUM HIGH m-1 Approx 70% = 490 Watts
18 sec. ON 14 set OFF
MEDIUM m-1 .Approx 50% = 350 Watts
12 sec. ON 20 set OFF
MEDIUM LOW J-1 Approx 30% = 210 Watt:
6 set ON 26 set OFF
LOW J] Approx 10% = 70 Watts
NOTE: The ON/OFF time ratio does not exactly corre-
spond to the percentage of microwave power,
because approx. 2 seconds are needed for
heating up the magnetron filament.
FUNCTION OF IMPORTANT COMPONENTS
DOOR OPEN MECHANISM
The door can be opened by pushing the door open
button on the control panel. When the door open
button is pushed, the switch lever is moved upward,
operating the latch head. The latch head is moved
upward, and released from the latch hook. Now, the
door can be opened.
Door
Latch hook
Latch
head \
2nd latch switch
Do
1st latch switch
IST LATCH SWITCH SW1
2ND LATCH SWITCH SW2
STOP SWITCH SW4
1. When the oven door is closed, the contacts (COM
- NO) must be closed.
2. When the oven door is opened, the contacts (COM
- NO) must be opened.
MONITOR SWITCH SW3
1. When the oven door is closed, the contacts
(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 the contacts
(COM - NO) of the 1st and 2nd latch switches fail
to open, the fuse M6.3A blows simultaneously with
closing the contacts (COM - NC) of the monitor
switch.
CAUTION: BEFORE REPLACING A BLOWN FUSE F
M6.3A TEST THE IST AND 2ND LATCH
SWITCHES, MONITOR SWITCH AND
MONITOR RESISTOR FOR PROPER OP-
ERATION. (REFER TO CHAPTER “TEST
PROCEDURE”.)
MONITOR RESISTOR R 0.8 i2 20W
The monitor resistor prevents the fuse M6.3A bursting
when the fuse M6.3A blows due to the operation of
the monitor switch.
\ Switch lever
Figure D-l. Door Open Mechanism

R -3A53
R-3A53B
ASYMMETRIC RECTIFIER
The asymmetric rectifier is a solid state device that
prevents current flow in both directions. And it pre-
vents the temperature rise of the power transformer by
blowing the fuse M6.3A when the high voltage rectifier
is shorted.
.+galG” VOLTAGERECTIFIER
The rated peak reverse voltage of Dl of the asymmetric
rectifier is 6 KV The rated peak reverse voltage of D2
of the asymmetric rectifier is 1.7 KV. Dl and D2 of the
asymmetric rectifier or high voltage rectifier are shorted
when the each peak reverse voltage goes beyond the
each rated peak reverse voltage. (The process of
blowing the fuse M6.3A.)
1. The high voltage rectifier is shorted by any causes
when microwave cooking.
2. The peak reverse voltage of D2 of the rectifier goes
beyond the rated peak reverse voltage 1.7 KV in the
voltage doubler circuit.
3. D2 of the rectifier is shorted.
4. The large electric currents flow through the high
voltage winding of the power transformer.
5. The large electric currents beyond 6.3A flow
through the primary widing of the power transfor-
mer.
6. The fuse M6.3A blows by the large electric currents.
7. The power supply to the all electrical parts is cut
off.
FUSE F M6.3A
1. The fuse M6.3A blows when the contacts (COM
- NO) of the 1st latch switch and 2nd latch switch
remain closed with the oven door open and when
the monitor switch closes.
2. The fuse M6.3A also blows when asymmetric
rectifier, H.V. rectifier, H.V. wire harness, H.V.
capacitor, magnetron or secondary winding of
power transformer is shorted.
3. If the wire harness or electrical components are
short-circuited, the fuse M6.3A blows to prevent
an electric shock of fire hazard.
NOISE FILTER
(FOR NEW ZEALAND)
The noise filter assembly prevents radio frequency in-
terference that might flow back in the power circuit.
TEMPERATURE FUSE TFI 150°C (MG)
This fuse protects the magnetron against overheating.
If the temperature goes up higher than 150°C because
the fan motor is interrupted, the air inlet duct is blocked
or the ventilation openings are obstructed, the fuse
blows and cuts off the power supplying to the power
transformer. The defective fuse must be replaced with
new rated one.
TEMPERATURE FUSE TF2 115°C
If the temperature of the temp. fuse goes up higher
than 115°C because the ventilation openings are ob-
structed, the fuse blows and cut off the power sup-
plying to the power transformer. The defective fuse
must be replaced with new rated one.
TEMPERATURE FUSE TF3 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 unproper setting of cook time or failure
of timer motor.
Under normal operation, the temperature fuse remains
closed. However, when abnormally high temperatures
are reached within the oven cavity, the temperature
fuse will open at 150°C, causing the oven to shut
down.
TURNTABLE MOTOR TTM
The turntable motor drives the roller stay to rotate the
turntable.
FAN MOTOR FM
The fan motor drives a blade which draws external cool
air. This cool air is directed through the air vanes sur-
rounding the magnetron and cools the magnetron.
This air is channeled through the oven cavity to remove
steam and vapors given off from the heating foods. It
is then exhausted through the exhausting air vents at
the oven cavity

R-3A53
R-3A53B
SERVICING
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.
REMEMBER TO CHECK 3D
1) Disconnect the supply.
2) Door opened, and wedged open.
3) Discharge high voltage capacitor.
REMEMBER TO CHECK 4R
1) Reconnect all leads removed from components
during testing.
2) Replace the outer case (cabinet).
3) Reconnect the supply.
WARNING AGAtNST THE CHARGE OF THE
HIGH-VOLTAGE CAPACITOR 4) Run the oven. Check all functions.
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 con-
necting lead of the high-voltage rectifier)
against the chassis with the use of an insu-
lated screwdriver.
Sharp recommend that wherever possible
fault-finding is carried out with the supply discon-
nected. It may in, some cases, be necessary to
connect the supply after the outer case has been
removed, in this event carry out $J checks and then
disconnect the leads to the prrmary of the power
transformer. Ensure that these leads remain isolated
from other components and the oven chassis. (Use
insulation tape if necessary.) When the testing is
completed carry out 3D checks and reconnect the
leads to the primary o-he power transformer.
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 microwave
timer for two (2) minutes. Set the power level to
HIGH and push the START button. When the two
minutes has elapsed (timer at zero) carefully check
that the water is now hot. If the water remains cold
carry out 30 checks and re-examine the con-
nections 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 a microwave leakage test carried out.
TROUBLESHOOTING GUIDE
When troubleshooting the microwave oven, it is
helpfull to follow the Sequence of Operation in per-
forming the checks. Many of the possible causes of
trouble will require that a specific 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 be-
cause of a blown fuse (M6.3A) in the
I-st latch switch - 2nd latch switch -
monitor switch - monitor resisitor cir-
cuit, check the 1st latch switch, 2nd
latch switch, monitor switch and
monitor resistor before replacing the
fuse (M6.3A).
7

R-3A53
R-3A53B
NOTE: “0” means direct cause and part. “A” means indirect cause and part. CK: CHECK, RE: REPLACE
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PROBLEM
Home fuse blows when power supply
cord is plugged into wall outlet.
Fuse M6.3A blows when power supply
cord is plugged into wall outlet. 00
88 : 88 does not appear in display but
OFF
CONDITION power supply cord is plugged into wall 00
outlet.
Display does not operate properly when
STOP/CLEAR pad is touched.
Oven lamp does not light at door
opened. (Display appears.)
Oven does not start when START pad
is touched. (Display appears.)
0
0
Oven lamp does not light. (Display
appears.)
Fan motor does not operate. (Display
appears.) 0
Turntable motor assembly does not
operate. (Display apears.) 0
Oven or any electrical parts does not
stop. But cooking time is 0 or
STOP/CLEAR pad is touched.
IIN
30NDITION Oven seems to be operating but little or
no heat is produced in oven load. (Micro- 000 00 0
wave power level is set at HIGH.)
Oven does not seem to be operating
properly when MEDIUM HIGH, MEDI-
UM, MEDIUM LOW or LOW is set. (Oven
operates properly at HIGH and then the
STOP/CLEAR pad is touched the oven
stops. )
Oven goes into cook cycle but shuts
down before end of cooking cycle. 0
* Oven stops as soon as when the START
pad is touched. n/\nr\r\r\
8

R-3A53
R-3A53B
CK: CHECK, RE: REPLACE
I I Y w w Y ?L
c3 u- u u :: :: u ii 5 v v :: 5 :: -I 2 z
00 00 0 0 0 0 0
I I I I I I I I I I I I I
0 0 0
lo~o~0~0~ 10 0
0 0 00
I I
000 ’ 00
I
0 0 /o/ 101 0
01 lOI IOI 0
-a 00
I I
0 00
I I I I
00
OOA n A0
0 0
9

R-3A53
R-3A53B
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
MAGNETRON TEST
NEVER TOUCH ANY PART IN THE CIRCUIT WITH YOUR HAND OR AN INSULATED I
TOOL WHILE THE OVEN IS IN OPERATION. !
CARRY OUT 30 CHECKS
Isolate the magnetron from the high voltage circuit by removing all leads connected to the filament
terminal.
To test for an open circuit filament use an ohmmeter to make a continuity test between the
magnetron filament terminals, the meter should show a reading of less than 1 ohm.
To test for a short circuit filament to anode condition, connect ohmmeter between one of the fil-
ament terminals and the case of the magnetron (ground). This test should be indicated an infinite
resistance. If a low or zero resistance reading is obtained then the magnetron should be re
g laced,
MICROWAVE OUTPUT POWER (2 liter water load) (R 82AOlU)
The following test procedure should be carried out with the microwave oven in a fully assembled
condition (with outer case fitted). Microwave output power from the magnetron can be measured
by way of substitution, i.e. it can be measured by using a water load how much it can be absorbed
by the water load. To measure the microwave output power in the microwave oven, the relation
of calorie and watt is used. When P(W) heating works for t(second), approximately P x t/4.2
calorie is generated. On the other hand, if the temperature of the water with V(ml) rises AT
(“C) during this microwave heating period, the calorie of the water is V x AT.
I The formular is as follows; I
P x t / 4.2 = V x AT P (W) = 4.2 x V x AT /t I
Our condition for the water load is as follows: 1
Room temperature .....................around 20°C Power supply Voltage .............Rated voltage
Water load ......2000 ml Initial temperature .......1O+ 1“C /
P=60xAT Heating time ...... 2min. 20 sec. /
J
Measuring method:
A) Use two 1 litre Pyrex beakers with a diameter of approximately of 12cms.
B) Place 1 litre of 10°C water in each beaker.
C) Mark Tl on the one beaker and mark T2 on the other one. And stir the water and measure the
temperature of water the thermometer and note them. The graduation of the thermometer must
be scaled by 0.1 “C at minimum and an accurate mercury thermometer is recommended.
D) Place the two beakers as touching each other in the centre of the cavity.
E) Set the timer to 2minute and 20 seconds at 100% power (the time required to raise the water
temperature 10 degrees C.)
F) The time must be measured with stopwatch or wristwatch.
G) After 1 minute and 52 seconds, stop the oven by opening the door.
H) Remove the two beakers from the oven and measure the temperature of the water by stiring the
water with the thermometer and noting the readings.
Example
Initial temperature ............................................................................... Tl = 10°C T2 = 11 “C /
Temperature after 2min. 20 sec. ........................................................ Tl = 20°C T2 = 21 “C I
Temperature difference Cold-Warm ........................................... AT1 = 10°C AT2 = 10°C
Mean temperature rise AT AT = (AT1 +AT2) / 2 = (IOOC + IO'C) / 2 = 10°C /
........ ;
Measured output power
The equation is “P= 60 x AT” =................................................... P= 60 x 10°C 600 Watts
NOTE: The measured output power should be at least +I5 % of the rated output
power.
CAUTION: 1°C CORRESPONDS TO 60 WATTS.
REPEAT MEASUREMENT IF THE POWER IS INSUFFICIENT.
10

R-3A53
R-3A53B
TEST PROCEDURES (CONT’D)
PROCEDURE
LETTER COMPONENT TEST
(Tl OC) (T2 OC) (T2 OCI
Heat up for 2min. 20 sec.
MICROWAVE OUTPUT POWER (IEC-705-1988) (RD82A02U)
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. To measure the microwave output power in the microwave oven, the relation of cal-
orie and watt is used. When P(W) heating works for t(second), approximately P x t/4.1 87 calorie
is generated. On the other hand, if the temperature of the water with V(ml) rises AT (“C) during
this microwave heating period, the calorie of the water is V x AT.
The formular is as follows;
Pxt/4.187=VxAT P(W)=4.187xVxAT/t
Our condition for the 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=70xAT
Measuring condition:
I. 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 fest.
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. Select stirring devices and measuring instruments in order to minimize addition or removal of
heat.
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” is measured while the microwave generator is operating at full power. Magnetron filament
heat-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.
11

R -3A53
R-3A53B
TEST PROCEDURES (CONT’D)
PROCEDURE
LETTER COMPONENT TEST
Measuring method:
1. Measure the initial temperature of the water before the water is added to the vessel
(Example: The initial temperature Tl = 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 va
(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. Caluculate the microwave power output p in watts from above formula.
ue A T of
Initial temperature ..................................................................................................... Tl = 11 “C
Temperature after (60 + 2) = 62 sec. .................................................................... T2 = 21 “C
Temperature difference Cold-Warm AT1 =
.................................................................... 10°C
Measured output power
The equation is “P= 70 x AT” P= 70 x 10°C =................................................... 700 Watts
JUDGMENT: The measured output power should be at least _+I5 % of the rated
output power.
CAUTION: 1°C CORRESPONDS TO 70 WATTS. REPEAT MEASUREMENT IF THE POWER IS
INSUFFICIENT.
T2”C
Heat up for 62 sec.
12

R-3A53
R-3A53B
TEST PROCEDURES (CONT’D)
PROCEDURE
LETTER COMPONENT TEST
B POWER TRANSFORMER TEST
WARNING: High voltages and large currents are present at the secondary wind-
r---- _
ing and filament winding of the power transformer. It is very dangerous to work
near this part when the oven is on. NEVER make any voltage measurements of the
high-voltage circuits, including the magnetron filament.
CARRY OUT 3D CHECKS.
Disconnect the leads to the primary winding of the power transformer. Disconnect the filament
and secondary winding connections 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 windings. The following
readings should be obtained :-
a. Primary winding ----------I .96 ohms approximately.
b. Secondary winding - -- - -- -97.2 ohms approximately.
c. Filament winding ---------less than 1 ohm.
If the reading obtained are not as stated above, then the power transformer is probably faulty
and should be replaced.
CARRY OUT 4R CHECKS
13

R-3A53
R-3A53B
TEST PROCEDURES (CONT’D)
PROCEDURE
LETTER COMPONENT TEST
C HIGH VOLTAGE RECTIFIER ASSEMBLY TEST
HIGH VOLTAGE RECTIFIER TEST
CARRY OUT 3D CHECKS.
Isolate the high voltage rectifier assembly from the HV circuit. The high voltage rectifier can be
tested using an ohmmeter set to its highest range. Connect the ohmmeter across the terminal
B+C of the high voltage rectifier and note the reading obtained. Reverse the meter leads and note
this second reading. The normal resistance is infinity in one direction and more than 100 kfI in
the other direction.
CARRY OUT $fj CHECKS
ASYMMETRIC RECTIFIER TEST
CARRY OUT 3D CHECKS.
Isolate the high voltage rectifier assembly from the HV circuit. The asymmetric rectifier can be
tested using an ohmmeter set to its highest range. Connect the ohmmeter across the terminals
A+B of the asymmetric rectifier and note the reading obtained. Reverse the meter leads and note
this second reading. If an open circuit is indicated in both directions then the asymmetric rectifier
is good. If a asymmetric rectifier is shorted in either direction, then the the asymmetric rectifier
is probably faultly and must be replaced with the high voltage rectifier. When the asymmetric
rectifier is defective, check whether magnetron, high voltage rectifier, high voltage wire or fila-
ment winding of the power transformer is shorted.
CARRY OUT 4J CHECKS
NOTE: FOR MEASUREMENT OF THE RESISTANCE OF THE RECTIFIER,
OF THE MEASURING INSTRUMENT MUST HAVE A VOLTAGE AT
BECAUSE OTHERWISE AN INFINITE RESISTANCE MIGHT BE S
DIRECTIONS.
THE BATTERIES
LEAST 6 VOLTS,
HOWN IN BOTH
D HIGH VOLTAGE CAPACITOR TEST
CARRY OUT 3D CHECKS.
A. Isolate the high voltage capacitor from the circuit.
B. Continuity check must be carried out with measuring instrument which is set to the highest
resistance range.
C. A normal capacitor shows continuity for a short time (kick) and then a resistance of about
10 MQ after it has been charged.
D. A short-circuited capacitor shows continuity all the time.
E. An open capacitor constantly shows a resistance about 10 Mf2 because of its internal 10
MI2 resistance.
F. When the internal wire is opened in the high voltage capacitor, the capacitor shows an in-
finite resistance
G. The resistance across all the terminals and the chassis must be infinity when the capacitor
is normal.
If incorrect readings are obtained, the high voltage capacitor must be replaced.
. CARRY OUT 4FJ CHECKS
14

R-3A53
R-3A53B
TEST PROCEDURES (CONT’D)
PROCEDURE
LETTER COMPONENT TEST
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
1 Plunger Operational ~~ C6M to NO I COM to NC 1
COM; Common terminal S.C.; Short circuit
NO; Normally open terminal O.C.; Open circuit
NC; Normally closed terminal
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 temp. fuse.
Then using an ohmmeter, make a continuity test across the two terminals as described in the
table below.
CARRY OUT 4R CHECKS
Table: Temperature Fuse or Thermal Cut-out Test
Temperature of Temperature of Indication of
“ON” condition “OFF” condition ohmmeter
Parts Name (closed circuit). (open circuit). (When room
(“Cl (“C) temperature is
approx. 20°C.)
Temp. fuse 150°C This is not resetable Above 150°C Closed circuit
(MG) type.
Temp. fuse This is not resetable Above 115°C Closed circuit.
115Oc type
Temp. fuse 150°C This is not resetable Above 150°C Closed circuit
(OVEN) type.
If incorrect readings are obtained, replace the temp. fuse or thermal cut-out.
An open circuit temperature fuse 150°C indicates that the magnetron has overheated, this may
be due to resistricted ventilation, cooling fan failure or a fault condition within the magnetron
or HV circuit.
An open circuit temp. fuse 150°C (OVEN) indicates that the oven cavity has over heated, this
may be due to no load operation or catching fire of foods in the oven cavity.
An open circuit temp. fuse 115°C indicates that the inner parts of the oven have overheated, this
may be due to resisted ventilation.
An open circuit temperature controller indicators that the steam duct reaches high temperature.
15

R-3A53
R-3A530
TEST PROCEDURES (CONT’D)
PROCEDURE
LETTER COMPONENT TEST
G MONITOR RESISTOR TEST
CARRY OUT 30 CHECKS.
Disconnect the leads from the monitor resistor or surge resistor.
Using an ohmmeter and set on a low range.
Check between the terminals of the monitor resistor or surge resistor as described in the follow-
ing table. Table: Resistance
Resistor I Resistance -1
Monitor resistor Approx. O.Sn I
If incorrect readings are obtained, replace the monitor resistor or surge resistor
CARRY OUT 4R CHECKS.
H 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
IM
otors Resistance
1 F
an motor 1 Approximatelv 252 ohms
1Turntable motor 1 Approximately 13.75 kohms
If incorrect readings are obtained, replace the motor.
(Also refer to test procedure I)
CARRY OUT 4R CHECKS
LIVE TEST FOR MOTOR WINDINGS
CAUTION: The following procedure requires the oven to be connected to the supply
and should only be used if the relevant “cold” checks for the motor un-
der test are inconclusive.
1. CARRY OUT 3D CHECKS
2. Disconnect the leads from the primary of the power transformer. Make sure that the leads
remain isolated from other oven components and chassis. (Use insulation tape if necessary.)
3. Connect a voltmeter, set to 250V AC, across the motor terminals. (Refer to the relevant motor
test procedure or pictorial diagram for the correct terminal numbers.)
4. Arrange the meter in a position where it can be read during the test. (Do not touch the meter,
meter leads or oven circuitry while the oven is active.)
5. Close the oven door.
6. Set the reievant timer for about three (3) minutes, set the power level to HIGH and push the
START button.
7. Note the reading on the meter and carefully observe the motor under test to see if it is turning.
8. CARRY OUT 3D CHECKS
9. Remove test meter leads.
1O.Reconnect the leads to the primary of the power transformer.
If a reading of 240 volts AC was obtained (step 7) but the motor was not turning then it is faulty
and should be replaced. If the meter indicated that no supply was present then the wiring to the
motor should be checked for continuity.
16

R-3A53
R-3A53B
TEST PROCEDURES (CONT’D)
PROCEDURE
LETTER COMPONENT TEST
NOISE FILTER TEST
WHT
CARRY OUT 3D CHECKS
Disconnect the leads from the terminals Rl 10 M ohm f 20%
of the noise filter.
Using an ohmmeter, check between the
terminals as described in the following
L iminl cxtzo%
l.OmH 0 06&F
R2 1 5 M ohm f 20%
CvtZo?d
0 0022,1F
table.
MEASURING POINTS ------I- INDICATION OF OHMMETER
Between N and L Approximately 1.5M0
Between terminal N and WHITE Short circuit
Between terminal L and RED ! Short circuit
If incorrect readings are obtained, replace the noise filter unit. CARRY OUT 4R CHECKS
K BLOWN FUSE F M6.3A
CARRY OUT 3D CHECKS
1. If the fuse M6.3A is blown, there could be a shorts or ground in electrical parts or wire har-
ness. Check them and replace the defective parts or repair the wire harness.
2. If the fuse M6.3A is blown when the door is opened, check the 1st latch switch, 2nd latch
switch, monitor switch and monitor resistor.
If the fuse M6.3A is blown by incorrect door switching replace the defective switch(s) and
the fuse M6.3A.
3. If the fuse M6.3A is blown, there could be a short in the asymmetric rectier or there could be
a ground in wire harness. A short in the asymmetric rectifier may have occured due to short
or ground in H.V. rectifier, magnetron, power transformer or H.V. wire. Check them and re-
place the defective parts or repair the wire harness.
CARRY OUT 4R CHECKS
CAUTION: Only replace fuse with the correct value replacement.
17

R-3A53
R-3A53B
TEST PROCEDURES (CONT’D)
PROCEDURE
LETTER COMPONENT TEST
TOUCH CONTROL PANEL ASSEMBLY TEST
The touch control panel consists of circuits including semiconductors such as LSI, I&, etc.
Therefore, unlike conventional microwave ovens, proper maintenance cannot be performed with
only a voltmeter and ohmmeter.
vided into two units, Control In this service manual, the touch control panel assembly is di- Unit and Key Unit, and troubleshooting by unit replacement is de-
scribed according to the symptoms indicated.
1. Key Unit.
The following symptoms indicate a defective key unit. Replace the key unit.
a) When touching the pads, a certain pad produces no signal at all.
b) When touching a number pad, two figures or more are displayed. .
c) When touching-the pads, sometimes a pad produces no signal.
2. Control Unit
The following symptoms indicate a defective control unit. Replace the control unit.
2-l In connection with pads.
a) When touching the pads, a certain group of pads do not produce a signal.
b) When touching the pads, no pads 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.
d) The corresponding segments 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 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.
d) Proper temperature measurement is not obtained.
M 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 fine foil pattern added to the
primary on the PWB, this foil pattern acts as a fuse. If the foil pattern is open, follow the trou-
bleshooting guide given below for repair.
Problem: POWER ON, indicator does not light up.
STEPS OCCURANCE CAUSE OR CORRECTION
1 ‘The rated AC voltage is not present at POWER ter- Check supply voltage and oven power cord. Please
minal of CPU connector (CN-A) use term “Low voltage transformer” when refering to
transformer Tl
r 2 The rated AC voltage is present at primary side of low Low voltage transformer or secondary circuit defec- voltage transformer. tive. Check and repair.
3 Only pattern at “a” is broken. ‘Insert jumper wire J3 and solder.
- --
4 Pattern at “a” and “b” are broken. *Insert the coil RCILF2003YAZZ between “c”
i-- “d”.
NOTE:’ At the time of these repairs, make a visual in-
spection of the varistor for burning damage
and examine the transformer with tester for the
presence of layer short-circuit (check primary
coil resistance).
If any abnormal condition is detected, replace
the defective parts.
I
D82
I
18

R-3A53
R-3A53B
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) Key Unit
(2) Control Unit
The principal functions of these units and the signals
communicated among them are explained below.
Key Unit
The key unit is composed of a matrix, signals generated
in the LSI are sent to the key unit through SO-S6.
When a key pad is touched, a signal is completed
through the key unit and passed back to the LSI
through K4-K7 to perform the function that was re-
quested.
Control Unit
Control unit consists of LSI, power source circuit,
synchronizing signal circuit, ACL circuit, buzzer circuit
and indicator circuit.
1) LSI
This LSI controls the key strobe signal, relay driving
signal for oven function and indicator signal.
2) Power Source Circuit
This circuit generates voltage necessary in the
control unit.
Svmbol Voltaae Aoolication
VDD -12v LSI (ICI ), ACL circuit
VREF
VP al&v LSI (ICI) Fluorescent display tube : Grid
and anode voltage
VFI 3V P-P Fib”,“ent of fluorescent display
VF2 (VFI to VF2 voltage)
3) 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.
4) ACL Circuit
A circuit to generate a signal which resets the LSI
to the initial state when power is supplied.
5) Buzzer Circuit
The buzzer is responsive to signals from the LSI
to emit noticing sounds (key touch sound and
completion sound).
6) Door Sensing Switch
A switch to “tell” the LSI if the door is open or
closed.
7)
8)
Relay Circuit
To drive the magnetron, fan motor, turntable motor
and light the oven lamp.
Indicator Circuit
Indicator element is a Fluorescent Display.
Basically, a Fluorescent Display is a triode having
a cathode, a grid and an anode. Usually, the cath-
ode of a Fluorescent Display is directly heated and
the filament serves as cathode.
The Fluorescent Display has 6-digits, 13-segments
are used for displaying figures.
19