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
TOUCH CONTROL ASSEMBLY? cccic.t.ccists locas da caaciaciccceqcug colette denvevevensetesdtanacedluardaieevebestsvgerbvoauenceusuaers 7
COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE .0000.. ee eeseeeeeeseneseeeseeeeteeneeeeeaeaeen 2
MICROWAVE MEASUREMENT ....0......ccccecscccsscssssessssasceecseeecsaeesseseeaeeeeesesdeceeeseaueseaeseaeseeeessecaneeseaeeeees -
TEST DATAAT: A GLANCE iicsiiscccsecetiscwterssstusscsevsosevstarversertibecdvecesisusracacepeasduclasasndaasnbdasiedaddaednert ofimeersen -
WIRING: DIAGRAM ci. cis. ccei. onteates sleseesgidscevandiihanadsvents oseusvacoucededede cutpa sunceviiisdesced GewsdeeavaeVediwedandassdhastactudsTaaiy . 30
PICTORIAL DIAGRAM 5.150200 sSasvesezdisiasheiue dosdiusecastasacasaecoats Saceydsnscedents sgeveuct suuusvaeaasebadaaceustsecasacasaddapeadenesin - 31
CONTROE PANEL: GIRCUUID: i screed ccistesniccucctceSccuseeesgesscedecesatd osat tuakbeupccspensygtoundads cvuadcvesuudyandeacenucned tee oa . 32
PRINTED WIRING DIAGRAM 3... nec. ccs cccaescececcceti eceaiecnsatuteancteasasseveuceaweswedecentensencusicuved dvlesuteaanaedueevevedn - 33
PARTS EIST vncisvcccesevssessccsennancvtssatvctevesssadataobetisveresbevesveecacedseaedecutesdtctacesuepiucveleadvansdeusastcenedtduasuvestdeteeercnia - 34
PACKING AND ACCESSORIES .0......cccccccssesssssesceescseeseceesseeeeneeeteeeeeeesaesesueeanessanesassessesesseseeseneasenaeseessar - 39
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)
[esr proceune JA] 8] COE [EEE] Flap [sa
Mi epluilulel2imi]s|]r]el|nimMielr
AlolvivilrRInilo|tilHluloloitalu
clwl|.]|.trlolnwlo]lels|rininie
N|E clmM]|.{/i}]e}]erielsia N
E}R|R]A;Aalilt M E/|t|mM{T
E/PirR{|Alols|aler olola
POSSIBLE CAUSE R/TtTlc}lajly}lTr]R{/|wilcel] 7]/rl] eit s
AND Pree ale colabale taal
LI a c L/R] RIE
DEFECTIVE PARTS N| FI TIA wilclu|]*/tle
sS}/1}o]Tt{]s]i]H}] tr] Ale]s M
FIlE{R|cilwli|t l R | I O
Oo} R H]/1ic¢ 0 S T
R TI H U T O
MIA sic T O R
E| S wl R
R| Ss 1
E T
M Cc
B H
L
Y
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.