Sharp R-3A56(W) User manual

A-3A56(W)
R-3A56(B)
SHARP. SERVICE MANUAL
MICROWAVE OVEN
MODELS R-3A56(W)
R-3A56(B)
R-3A56 In interests of user-safety the oven should be restored to its original
condition and only parts identical to those specified should be used.
TABLE OF CONTENTS
Page
CAUTION, MICROWAVE RADIATION
GENERAL IMPORTANT INFORMATION, WARNING
PRODUCT SPECIFICATIONS
APPEARANCE VIEW
OPERATION SEQUENCE
FUNCTION OF IMPORTANT COMPONENTS
SERVICING
TEST PROCEDURE
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SHARP CORPORATION

R-3A56(W)
R-3A56(B)
CAUTION
MICROWAVE RADIATION
Personnel should not be exposed to the mircowave energy which may radiate from the magnetron or
other microwave generating devices if it is improperly used or connected. All input and output micro-
wave connections, waveguides, flanges and gaskets must be secured. Never operate the device with-
out a microwave energy absorbing load attached.
Never look into an open waveguide or antenna while the device is energised.
VARNING
MIKROVAGSSTRALING
Personal far inte utsattas for mikrovagsenergi som kan utstrala fran magnetronen eller andre
mikrovagsalstrande anordningar om dessa 4r felanslutna eller anvands pa fel satt. Alla in-och
utgangsanslutningar for mikrovagor, vagledare, flansar och packningar maste vara fast anslutna.
Mikrovagsgeneratorn far inte arbeta utan att absorberande belastning ar ansluten. Titta aldrig ini en
dppen vagledare eller antenn nar mikrovagsgeneratorn ar pakopplad eller laddad.
= VAROITUS
MIKROAALTOSATEILYA
Kayttaja ei saa joutua alttiiksi mikroaaltoenergialle, jota voi sateilla magnetronista tai muusta
mikroaaltoja kehittavasta laitteesta, jos sita kaytetaan vaarin tai jos se kytketaan vaarin. Kaikkien
mikroaaltoliitantéjen seka sy6ttd-etta ulostulopuolella, aaltoputkien laippojen ja tiivisteiden tulee olla
varmistettuja.
Mikroaaltouunia ei koskaan saa kayttaa ilman kuormaa jossa mikroaaltoenergiaa kuluu. Avoimeen
aaltoputkeen tai antenniin ei koskaan saa katsoa virran ollessa kytkettyna.
ADVARSEL —
MIKROBOLGESTRALING
Personell ma ikke utsettes for mikrobglge-energi som kan utstrales fra magnetronen eller andre
mikrobelge-generende deler dersom apparatet feilbetjenes eller blir feiltikoplet. Atle inn-og ut-
tilkoplinger i forbindelse med mikrobalge-stralingen, belgeledere, flenser og tetningsringer/pakninger ma
festes ordentlig.
Aldri bruk apparatet med mindre en mikrobalge-absorberende last er plassert i ovnsrommet. Aldrise
direkte inn i en Apen belgeleder eller antenne imens apparatet er stramfgrende.
ADVARSEL
MIKROBOLGEBESTRALING
Man bor ikke udszette sig for mikrobalgebestraling fra magnetronen eller andre
mikrobglgefrembringende anordninger, hvilket kan ske hvis apparatet er forkert tilsluttet eller bruges
forkert. Alle mikrobelgeindgange og-udgange, baigeledere, flanger og tezetningsstrimler ma veere
forsvarligt udfgrt.
Anvend aldrig ovnen uden en mikrobelgeabsorberende anordning. Se aldrig ind i en Aben bgigeleder
eller antenne, mens ovnen er i brug.

SERVICE MANUAL
SHARP
MICROWAVE OVEN
R-3A56(W) / R-3A56(B)
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.
The parts marked "*" are used at voltage
more than 250V. (Parts List)
Delar market med "*“ har en spanning
éverstigande 250V.
Huolto-chjeeseen merkitty. "tahdelia" osat
joissa jannite on yli 250V.
Deler som er merket “asterisk” er utsatt for
spenninger over 250V til jord.
Dele mzerket med stjerne benyttes med
hojere speending end 250 volt.
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 voltages more
than 250V.
Removal of the outer wrap gives access to potentials above
250V.
SHARP CORPORATION
OSAKA, JAPAN
R-3A56(W)
R-3A56(B)
| PRODUCT SPECIFICATION
GENERAL INFORMATION
APPEARANCE VIEW
| OPERATING SEQUENCE
| FUNCTION OF IMPORTANT
| COMPONENTS
ISERVICINGAND ~—
| TROUBLESHOOTING CHART
t TEST PROCEDURE “~E
TOUCH CONTROL PANEL
ADJUSTMENT PROCEDURE
MICROWAVE MEASUREMENT
| TEST DATA AT A GLANCE
WIRING DIAGRAM
PARTS LIST

R-3A56(W)
R-3A56(B)
PRODUCT SPECIFICATIONS
SPECIFICATION
ITEM DESCRIPTION
Power Requirements 220 -230 Volts
50 Hertz
Single phase, 3 wire grounded
Power Consumption 1.5 kW
Power Output Q900W watts nominal of RF microwave energy
(measured by way of IEC 705)
Operating frequency of 2450 MHz
Case Dimensions Width 450mm
Height 295mm including foot
Depth 360mm
= Cooking Cavity Dimensions Width 290mm
Height 174mm
Depth 313mm
Tumiabie diameter
Control Complement Touch Control System
Clock(1:00-12:59 or 0:00-23:59)
Microwave Power for Variable Cooking
Repetition Rate;
Full power throughout the cooking time
approx. 70% of Full Power
approx. 50% of Full Power
approx. 30% of Full Power
approx. 10% of Full Power
AUTO MINUTE pad
START pad
POWER LEVEL pad
STOP/CLEAR pad
Time pads
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-3A56(W)
R-3A56(B)
APPEARANCE VIEW
OVEN
Door — Tumtable
Door hinges
Waveguide cover
Contol panel
Door
lock
openings
————
Roller
stay
Oven
cavity
Door
seals
and
sealing
surfaces
|
Safety door latches
Ventilation openings
0. Outer case
1. Power supply cord
A SOON DARWN =
Seal packing
1. Place the roller stay on the floor of
the oven cavity.
2. Then place the turntable on it fitting
to the coupling.
THE AUTO-TOUCH CONTROL PANEL
More Indicator
Less Indicator
Low Indicator
Med/Low indicator
Med indicator
Med/High indicator
High indicator
Digital display
Pieces indicator
. Unit weight indicator
. Cook indicator
. Snack keys
. Potato keys
. Instant action keys
. More/Less keys
. Time keys
. Timer/Hold key
. Clock set key
. Power level key
. Stop key
. Auto minute/Start key
. Door open button
© ODNAaAPR WON >
[Onn © a a en i
N+] CO DAN DAR WN = OC

R-3A56(W)
R-3A56(B)
OPERATING SEQUENCE
OFF CONDITION
Closing the door activates all door interlock switches (pri-
mary 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 pluged in a wall outlet (240V
50H2), the line voltage is supplied to the point A3+A5 in the
control unit.
Figure O-1 on page 30
—
. The display flashes "88:88".
2. Toset any programmes or set the clock, you must first
touch the STOP pad.
3. “88:88” 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 Time pad
and start the oven with touching START pad.
Function sequence Figure 0-2 on page 30
CONNECTED COMPONENTS RELAY
Oven famp, Fan motor, Turntable motor RY1
Power transformer RY2
1. The line 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 voltagedoubling circuit, where it is doubled to
negative voltage of approximately 4000 volts D.C..
3. 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.
4. 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.
5. 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)
Primary 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 primary latch
switch, 2nd latch switch and stop switch are made open.
The oven jamp remains on even if the oven door is
opened after the cooking cycle has been interrupted,
because the relay RY1 stays closed. Shown in the display
is the remaining time.
6. MONITOR SWITCH CIRCUIT
The monitor switch (SW3) is mechanically controlled by
oven door, and monitors the operation of the 1st latch
switch (SW1)
6-1 When the oven door is opened during or after the
cycle of cooking program, the primary latch switch
(SW1), and stop switch (SW4) must open their contacts
first. After that the contacts (COM - NC) of the monitor
switch (SW3) can be closed and then contacts of the
2nd latch switch (SW2) can be opened.
6-2 When the oven door is closed, the contacts
(COM - NC) of the monitor switch (SW3) must be
opened and contacts (COM - NO) of the 2nd latch
switch (SW2) must be closed first. After that the
contacts of the primary latch switch (SW1) and stop
switch (SW4) are closed.
6-3 When the oven door is opened and the contacts of the
primary latch switch (SW1) remain closed, the fuse
(F) F7.4A will blow, because the monitor switch is
closed and a short circuit is caused.
HIGH, MEDIUM HIGH, MEDIUM, MEDIUM
LOW, LOW COOKING
When the microwave oven is preset for variable cooking
power, the line voltage 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
(RY2). The following levels of microwave power are given.
SETTING 32 sec. ON
HIGH
24 sec. ON 8 sec. OFF
MEDIUM
HIGH
Approx.
70%
=
630
Watts
18 sec. ON 14 sec. OFF ‘
MEDIUM
kx
°°»
&
|
Approx.
50%
=
450
Watts
- 12 sec. ON 20 sec. OFF
MEDIUM
LOW
Approx.
30%
=
270
Watts
6 sec. ON 30 sec. OFF
NOTE: The ON/OFF time ratio does not exactly correspond
to the percentage of microwave power, because
approx. 2 seconds are needed for heating up the
magnetron filament.

R-3A56(W)
R-3A56(B)
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 cook 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
STOP
SWITCH
LATCH HOOK
2ND LATCH
SWITCH
MONITOR
SWITCH
LATCH
HEADS
pamany LATCH
CH
OPEN LEVER
DOOR OPEN BUTTON
Figure D-1. Door Open Mechanism
PRIMARY LATCH SWITCH (SW1)
2ND LATCH SWITCH (SW2)
apr SWITCH (SW4)
. When the oven door is closed, the contacts (COM - NO)
must be closed.
2. When the oven dooris opened, the contacts (COM - NO)
must be opened.
MONITOR SWITCH (SWS)
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 primary latch switch (SW1) fail to open, the fuse
F7.4A blows simultaneously with closing the contacts
(COM - NC) of the monitor switch (SW3).
CAUTION: BEFORE REPLACING A BLOWN FUSE (F)
F7.4A TEST THE PRIMARY LATCH SWITCH
(SW1), MONITOR SWITCH (SW3) AND
MONITOR RESISTOR FOR PROPER
OPERATION. (REFER TO CHAPTER "TEST
PROCEDURE”.)
MONITOR RESISTOR 0.80hm 20W
The monitor resistor prevents the maximum breaking ca-
pacity of the F7.4A fuse from being exceeded due to
operation of the monitor switch
ASYMMETRIC RECTIFIER
The asymmetric rectifier is a solid state device that prevents
current flow in both directions. And it prevents the tempera-
ture rise of the power transformer by blowing the special
fuse F7.4A when the high voltage rectifier is shorted.
ASYMMETRIC Le
RECTIFIER
HIGH VOLTAGE RECTIFIER
The rated peak reverse voltage of D1 of the asymmetric
rectifier is 6 KV. The rated peak reverse voltage of D2 of the
asymmetric rectifier is 1.7 KV. D1 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 F7.4A.)
1. The high voltage rectifier is shorted by anycauses when
microwave cooking or dual 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.
. D2 of the rectifier is shorted.
. The large electric currents flow through the high voltage
winding of the power transformer.
5. The large electric currents flow through the primary
winding of the power transformer.
. The fuse F7.4A blows by the large electri currents.
7. The power supply to the power transformer is cut off.
mee)
ao
Pagar F7.4A
The fuse F7.4A blows when the contacts ((OM- NO) of
the primary latch switch (SW1) remain cls ed with the
oven door open and when the monitor switch (SWS)
closes.
2. The fuse F7.4A also blows when asymmetric rectifier,
H.V. rectifer, H.V. wire harness, H.\. capacitor,
magnetron or secondary winding of powe transformer
is shorted.
3. If the wire harness or electrical components are short-
circuited, the fuse F7.4A blows to prevent an electric
shock or fire hazard.
THERMAL CUT-OUT 145°C TC1 (MG)
The thermai cut-out protects the magnetron against ove r-
heat. if this temperature goes up higher tha 145°C be-
cause the fan motor is interrupted, the ventilaio n openings
are blocked, the thermal cut-out (TC1) will men and line
voltages to the power transformer will be cut off and the
operation of the magnetron will be stopped. Th © defective
thermal cut-out (TC1) must be replaced withnéw one.

R-3A56(W)
R-3A56(B)
THERMAL CUT-OUT 125°C TC2 (OVEN)
The thermal cut-out 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 control unit. Under normal
operation, the oven thermal cut-out remains closed. How-
ever, when abnormally high temperatures are reached
within the oven cavity, the oven thermal cut-out will open at
125°C, causing the oven to shut down. The defective
thermal cut-out (TC2) must be replaced with 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
channeled 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.
NOISE FILTER
The noise filter prevents the radio frequency interference
that might flow back in the power circuit.

R-3A56(W)
R-3A56(B)
SERVICING
WARNING TO SERVICE PERSONNEL
Microwave ovens contain circuitry capable of producing very high voltage and current, contact with following parts:
High voltage capacitor, Power transformer, Magnetron, High voitage rectifier assembly, High voltage harness.
REMEMBER
TO
CHECK
3D
REMEMBER
TO
CHECK
4R
.
1)
Reconnect
all
leads
removed
from
components
1)
Disconnect
the
supply.
during
testing.
2)
Door
opened,
and
wedged
open.
2)
Replace
the
outer
case
(cabinet).
3)
Discharge
high
voltage
capacitor.
3)
Reconnect
the
supply.
WARNING AGAINST THE CHARGE OF THE 4) Run the oven. Check all functions.
HIGH-VOLTAGE CAPACITOR 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
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 power level to HIGH and push the START button. When
connection of the high-voltage capacitor (that is,
of the connecting lead of the high-voltage recti-
fier) against the chassis with the use of an insu-
lated screwdriver.
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.
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
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 re-
main 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 of the power transformer.
When all service work is completed, and the oven is fully assembled, the microwave power output shouldbe
checked and a microwave leakage test carried out.
TROUBLESHOOTING GUIDE
When troubleshooting the microwave oven, it is helpful to IMPORTANT: If the oven becomes inoperatve because
follow the Sequence of Operation in performing the checks. of a blown fuse F7.4A in the prirmary latch
Many of the possible causes of trouble will require that a switch - monitor switch - moritor resistor
specific test be performed. These tests are given a proce- circuit, check the primary lach switch,
dure letter which will be found in the "Test Procedure” monitor switch and monitor resistor before
section. replacing the fuse F7.4A.

R-3A56(W)
R-3A56(B)
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PROBLEM
Home fuse blows when power cord is plugged
into wall outlet.
Fuse F7.4A blows when power cord is plugged
into wall outlet.
“88:88” dose not appear in display when power
cord is plugged into wall outlet.
Display does not operate properly when
STOP/CLEAR pad is touched.
OFF
CONDITION
Oven lamp does not light when door is opened.
(Display appears.)
:)
Oven does not start when START pad is touched.
(Display appears
Oven lamp does not light. (Display appears.)
Fan motor does not operate. (Display appears.)
Turntable motor assembly does not operate.
(Display appears.)
Oven or electrical parts do not stop when
cooking time is 0 or STOP pad is touched.
Oven seems to be operating but little or no heat is
produced in oven load. (Microwave power level is
set at "HIGH”)
Oven does not operate properly during the variable
cooking condition except"HIGH” cooking condition.
(Oven stops when STOP pad is touched.)
Oven goes into cook cycle but shuts down before
end of cooking cycle.
COOKING
CONDITION
Oven stops as soon as the START pad is touched.

R-3A56(W)
R-3A56(B)
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R-3AS6(W)
R-3A56(B)
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
A MAGNETRON TEST
NEVER TOUCH ANY PART IN THE CIRCUIT WITH YOUR HAND OR AN INSULATED TOOL
WHILE THE OVEN IS IN OPERATION.
CARRY OUT 3D CHECK
Isolate the magnetron from 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 filament to anode condition, connect ohmmeter between one of the filament 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 replaced.
MICROWAVE OUTPUT POWER (IEC-705-1988)
The following test procedure should be carried out with the microwave oven in a fully assernbled
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 calorie and watt is used.
When P(W) heating works for t(second), approximately P x t/4.187 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 formula is as follows;
Pxt/4.187=VxAT P (W) = 4.187 x VxAT/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
P= 89x AT
Measuring condition:
1. Container
The water container must be a cylindrical borosilicate glass vessel having a maximum naterial
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 fina water
temperature and the ambient temperature is 5K.
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 filamert heat-
up time is not included.
NOTE: The operation time of the microwave ovenis "t+ 3” sec. 3 sec. is magnetron filament heat-u> 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 values T of
(10+ 2) K. ,
5. Stir the water to equalize temperature throughout the vessel.
10

R-3A56(W)
R-3A56(B)
TEST PROCEDURES (CONT'D)
PROCEDURE
LETTER COMPONENT TEST
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.
Initial temperature
Temperature after (47 + 3) = 50 SCC. oo. cecccssesesecssesseeeseeeseeeeeeesseesessesceesseeensesanentengs T2 =21°C
Temperature difference Cold-Warm AT1 = 10°C
Measured output power
The equation is “P "= 89 x AT”
JUDGEMENT: The measured output power should be at least + 15 % of the rated output power.
CAUTION: 1°C CORRESPONDS TO 89 WATTS. REPEAT MEASUREMENT IF THE POWER IS
INSUFFICIENT.
Heatup for 50sec.
A ee
B WER TRANSFOR EST |
WARNING: High voltages and large currents are present at the secondary winding 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 measuremerts 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 flament and
secondary winding connections from the rest of the HV circuitry. Using an ohmmeter, set ona low range,
it is possible to check the continuity of all three windings. The following readings should be obtained:-
a. Primary winding ............ 1.4 ohms approximately
b. Secondary winding ....... 93 ohms approximately
c. Filament winding ........... less than 1 ohm
If the reading obtained are not stated as above, then the power transformer is probably fault; and should
be replaced.
CARRY OUT 4R CHECKS
Cc 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 cium be tested
using an ohmmeter set to its highest range. Connect the ohmmeter across the terminal B+ ¢ ofthe high
voltage rectifier and note the reading obtained. Reverse the meter leads and note this securid reading.
The normal resistance is infinite in one direction and more than 100 kQ in the other direcion.
1

R-3A56(W)
R-3A56(8)
PROCEDURE
LETTER
TEST PROCEDURES (CONT'D)
COMPONENT TEST
CARRY OUT 4R CHECKS
ASYMMETRIC RECTIFIER TEST
ASYMMETRIC
RECTIFIER
CARRY
OUT
3D
CHECKS.
C
Lg?
HIGH VOLTAGE RECTIFIER
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 an
asymmetric rectifier is shorted in either direction, then the asymmetric rectifier is probably faulty 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 filament winding of the power transformer is
shorted.
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 RESISTANCE MIGHT BE SHOWN IN BOTH DIRECTIONS.
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.
. Anormal capacitor shows continuity for a short time (kick) and then a resistance of about 10 M(2 after
it has been charged.
. Ashort-circuited capacitor shows continuity all the time.
. An open capacitor constantly shows a resistance about 10 MQ because of its internal 10 MQ
resistance. ;
F. When the internal wire is opened in the high voltage capacitor, the capacitor shows an infinite
resistance.
G. The resistance across all the terminals and the chassis must be infinite when the capacitor is normal.
If incorrect reading are obtained, the high voltage capacitor must be replaced.
mo oO
CARRY OUT 4R CHECKS
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 COM to NO COM to NC COM; Common terminal
Short circut”——| NO; Normally open terminal
Open Circuit NC; Normally close terminal
if incorrect readings are obtained, make the necessary switch adjustment or replace the switch,
CARRY OUT 4R CHECKS.
12

R-3A56(W)
R-3A56(B)
TEST PROCEDURES (CONT'D)
PROCEDURE
LETTER
COMPONENT
TEST
F THERMAL CUT-OUT TEST
CARRY OUT 3D CHECKS
Disconnect
the
leads
from
the
terminals
of
the
thermal
cut-out.
Then
using
an
ohmmeter,
make
a
continuity test across the two terminals as described in the below.
CARRY OUT 4R CHECKS
Temperature
of
“ON”
condition
(CloS@d
CIFCUIt)
«2...
eects
teteseeteseesteeeeecesensnessteatneataeneseeeesnenenanenenes
This
is
not
resetable
type
Temperature
of
“OFF”
condition
(open
circuit)
Above
125/145°C
Indication
of
ohmmeter
(When
room
temperature
is
APPFOX.
20°C.)
....eeseeseeeseesseeteeeteetetsererseeseerettetectseeeeesenes
Closed
circuit
If incorrect readings are obtained replace the oven 145°C thermal cut-out.
An
open
circuit
thermal
cut-out
(MG)
indicates
that
magnetron
has
overheated,
this
may
be
due
to
restricted
ventilation,
cooling
fan
failure
or
a
fault
condition
within
the
magnetron
or
HV
circuit.
An
open
circuit
thermal
cut-out
(OVEN)
indicates
that
the
foods
in
the
oven
may
catch
fire,
this
may
be
due
to
over
heating
produced
by
unproper
setting
of
the
cooking
timer
or
failure
of
the
control
panel.
ae
G BLOWN FUSE F7.4A
CARRY OUT 3D CHECKS
1.
Ifthe
fuse
F7.4A
is
blown,
there
could
be
shorts
or
grounds
in
electrical
parts
or
wire
harmess.
Check
them
and
replace
the defective
parts
or
repair
the
wire
harness.
2.
If
theF7.4A
is
blown,
there
could
be
a
short
in
the
asymmetric
rectifier
or
there
could
bea
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
replace
the
defective
parts
or
repair
the
wire
harness.
3.
If
the
fuse
F7.4A
is
blow
n
when
the
door
is
opened,
check
the
primary
latch
switch,
monitor
switch
and
monitor
resistor.
If the
fuse
F7.4A
is
blown
by
incorrect
door
switch
replace the
defective
switch (s)
and
thef use
F7.4A.
CARRY
OUT
4R
CHECKS
CAUTION:
Only
replace
special
fuse
F7.4A
with
the
correct
value
replacement.
i

R-3A56(W)
R-3A56(B)
TEST PROCEDURES (CONT'D)
PROCEDURE
LETTER COMPONENT TEST
H NOISE FILTER TEST
CARRY OUT 3D CHECKS
Disconnect the leads from the terminals of
the noise filter.
Using an ohmmeter, check between the ter-
: : L(min) Cx + 20% Cy + 20%
minals as described in the following table. Tom 0.068nF 0.0035uF
MEASURING POINTS
Between N and L Open circuit
Between terminal N and WHITE
Between terminal L and RED Short circuit
.ssp If incorrect readings are obtained, replace the noise filter unit.
CARRY OUT 4R CHECKS
I MONITOR RESISTOR TEST
CARRY OUT 3D CHECKS
Disconnect the leads from the monitor resistor. Using an ohmmeter and set on a low range.
Check between the terminals of the monitor resistor as described in the following table.
Table: Resistance
|
Approx.
430
If
incorrect
readings
are
obtained,
replace
the
monitor
resistor
or surge
resistor
CARRY OUT 4R CHECKS
J 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.
te
Table: Resistance of Motor
Resistance
Approximately 3602
Turntable motor Approximately 12kQ
lf incorrect readings are obtained, replace the motor. (Also refer to test procedure K)
CARRY OUT 4R CHECKS
14

R-3A56(W)
R-3A56(B)
TEST PROCEDURES (CONT'D)
PROCEDURE
LETTER COMPONENT TEST
K 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 under test are inconclusive.
—_
. 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.)
. 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 power level to HIGH and set the relevant timer for about three (3) minutes.
7. Note the reading on the meter and carefully observe the motor under test to see if it is turning.
8
9
1
aS
. CARRY OUT 3D CHECKS
. Remove test meter leads.
0. Reconnect the leads to the primary of the power transformer.
If a reading of the line voltage was obtained (step 7) but the motor was not turning then itis 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.
mr —————
L 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
Key Unit, and troubleshooting by replacement is described according to the symptoms indicated.
1. Key Unit. Note: Check key unit ribbon connection before replacement.
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 Panel
The following symptoms indicate a defective control unit. Before replacing the control unit,
perform the Key unit test(Procedure M) to determine if control unit is faulty.
2-1 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 fight 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 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.
15

R-3A56(W)
R-3A56(B)
TEST PROCEDURES (CONT'D)
PROCEDURE
LETTER
COMPONENT
TEST
KEY UNIT TEST
!f
the
display
fails
to
clearwhen
the
STOP
pad
is
depressed,
first
verify
the
flat
ribbon
is
marking
good
contact,
verify
that
the
door
sensing
switch(stop
switch)
operates
properly;
that
is
the
contacts
are
closed when
the door is
closed andopen
when
the
door is
open.
If the
door
sensing switch(stop
switch)
is
good,
disconnecct
the
flat
ribbon
cable
that
connects
the
key
unit
to
the
control
unit
and
make
sure
the
door
sensing
switch
is
closed
(either
close
the
door
or
short
the
door
sensing
switch
connecter).
Use
the
Key
unit
matrix
indicated
on
the
control
panel
schematic
and
place
a
jamper
wire
between
the
pins
that
correspond
to
the
STOP
pad
marking
momentary
contact.
If
the
control
unit
responds
by
clearing
with
a
beep
the
key
unit
is
faulty
and
must
be
replaced.
If
the
control
unit
does
not
respond,
it is
a
faulty and
must be
replaced.
If
a
specific
pad does
not
respond, the
above
method
may
be
used
(after
clearing
the
control
unit)
to
determine
if
the
control
unit
or
key
pad
is
at
fault.
CARRY OUT 4R CHECKS.
M RELAY TEST
CARRY OUT 3D CHECKS.
Remove the outer case and check voltage between Pin Nos. 3 and 5 of the 3 pin connector (A) on the
control unit with an A.C. voltmeter.
The meter should indicat 220~230 volts, if not check oven circuit.
RY1 and RY2 Relay Test
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,
RELAY SYMBOL rs eal alias CONNECTED COMPONENTS
VOLTAGE
Approx. 18.0V.D.C. Oven lamp/Turntable motor/Cooling fan motor

R-3A56(W)
R-3A56(B)
TEST PROCEDURES (CONT'D)
PROCEDURE
LETTER COMPONENT TEST
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 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 troubleshooting guide
given below for repair.
Problem: POWER ON, indicator does not light up.
CARRY OUT 3D CHECKS.
STEPS OCCURANCE CAUSE OR CORRECTION
1 The rated AC voltage is not present at Check supply voltage and oven power cord.
POWER terminal of CPU connector (CN-A)
ae The rated AC voltage is present at primary Low voltage transformer or secondary circuit defective.
side of low voltage transformer. Check and repair.
3 Only pattern at “a" is broken. *Insert jumper wire J1 and solder. (CARRY OUT 3D
CHECKS BEFORE REPAIR)
4 Pattern at "a" and "b" are broken. *Insert the coil RCILF2003YAZZ between "c" and "d".
(CARRY OUT 3D CHECKS BEFORE REPAIR)
NOTE: At the time of these repairs, make a
visual inspection of the varistor for burn-
ing damage and examine the transformer
with tester for the presence of layer
short-circuit (check primary coil resist-
ance). If any abnormal condition is de-
tected, replace the defective parts.
CARRY OUT 4R CHECKS.
17

R-3A56(W)
R-3A56(B)
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) Controt 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 R10-R13, R20
and R22. When a key pad is touched, a signal is com-
pleted
through
the
key
unit
and
passed
back
to
the
LSI
through ROO-RO3 to perform the function that was
requested.
Control Unit
Control
unit
consists
of
LSI,
power
source
circuit,
syn-
chronizing
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 voltages necessary in the control
unit.
Symbol__ Voltage Application
vc -5V LSI(IC1)
VP -32V Fluorescent display tube : Grid
and anode voltage
VFI
2.2Vac
Filament
of
fluorescent
display
tube
VF2 (VF1 to VF2 voltage)
18
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 signals 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 completionsound).
—
6) Door Sensing Switch (Stop Switch)
A switch to “tell” the LS! if the door is open or closed.
7
—
Relay Circuit
To drive the magnetron, fan motor, turntable motor and
light the oven lamp.
8) Indicator Circuit
Indicator element is a Fluorescent Display.
Basically, a Fluorescent Display is triode havinga cath-
ode, a grid and an anode. Usually, the cathode 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.
—