R4AlO
RQAZO
R4A30
SHARP SERVICE MANUAL
S8804R4AlOJ//
v.
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MICROWAVE OVEN
MODELS R-4Alo
R-4A20
R-4A30
Photo R-4AlO
In the interests of user-safety the set should be restored to its original
condition and only parts identical to those specified should be used.
(RDlGlOlU)
TABLE OF CONTENTS
Page
FOREWORD
.......................................................................................................................................................
1
CAUTION, MICROWAVE
RADIATION
..........................................................................................................
1
PRODUCT DESCRIPTION
...............................................................................................................................
2
OPERATION
.......................................................................................................................................................
4
SERVICING
........................................................................................................................................................
TOUCH
CONTROL
PANEL ASSEMBLY .....................................................................................................
1:
COMPONENT
REPLACEMENT AND
ADJUSTMENT
PROCEDURE
......................................................
20
MICROWAVE MEASUREMENT PROCEDURE
..........................................................................................
24
PICTORIAL
DIAGRAM ..................................................................................................................................
25
CONTROL
PANEL CIRCUIT
.........................................................................................................................
26
PRINTED
WIRING
BOARD ..........................................................................................................................
27
PARTS
LIST
....................................................................................................................................................
28
PACKING
AND ACCESSORIES
...................................................................................................................
34
SHARPCORPORATlON
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R4A20
R4A30
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Photo R-4A20
Photo RQA30
SERVICE MANUAL
SHARP
MICROWAVE OVEN
FOREWORD
This Manual has been prepared to provide Sharp Corp. Service
Personnel with complete Operation and Service information for the
SHARP MICROWAVE ovens, R4A10/R4AZ0/R4A30.
It is recommended that service personnel carefully study the
entire text of this manual so they will be qualified to render
satisfactory customer service.
Check interlock switches and door seal carefully. Special attention should be given to avoid electrical shock and microwave
radiation hazard.
(RD361 ON)
CAUTION
MICROWAVE RADIATION
Personnel should not be exposed to the microwave 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 ener
w
ized.
( D36201U)
SHAF?PCORPOf?ATtON
OSAKA, JAPAN
1 OPERATION
1 SERVICING
I
TOUCH CONTROL
.
PANEL ASSEMBLY
A
I
COMPONENT REPLACEMENT ’
AND ADJUSTMENT
PROCEDURE
A
I
MICROWAVE
1
MEASUREMENT
A
[ WIRING DIAGRAM
PRODUCT DESCRIPTION
EXPLANATION OF MICROWAVE COOKING
The Sharp Microwave Oven uses microwave energy to
produce heat in the food to be cooked. Unlike conventional ovens microwave energy will cook foods
without applying external heat.
Microwaves, which are short electromagnetic waves
of RF (radio frequency) energy, pass through materials
such as glass, paper, china and most plastics. Materi-
als such as metal and aluminum foil tend to reflect
microwaves and may be used only as recommended in
the cooking instructions.
Materials with a high
moisture content, like most foods, will absorb micro-
wave energy. As the microwave energy at a frequency
of 2450 Megahertz enters the food, the molecules align
themselves with the energy. Because the microwaves
are changing polarity every half cycle, the food molecules are changing direction every half cycle or oscillating back and forth 4,900,000,000 times per second.
This high speed oscillation causes friction between the
molecules, thereby converting the microwave energy
to heat.
(RD41101U)
SPECIFICATION
ITEM
Power Requirements
240 Volts
50 Hertz
DESCRIPTION
Power Consumption
Power Output
Case Dimensions
Single phase, 3 wire earthed
13oow
700 watts nominal of RF microwave energy (2 liter water load)
Operating frequency of 2450MHz
Width 520 mm
Height 318 mm including foot
Depth 393 mm
Cooking Cavity Dimensions
Width 345 mm
Height 217 mm
Depth 364 mm
Control Complement
t--r III-‘- 1-r
3631 vveignr
Touch Control System
Timer (0 - 99 min 99 sec. )
Microwave Power for Variable Cooking
Repetition Rate;
HIGH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
MED HIGH
Full power throughout the cooking time
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . approx.
70% of Full
MED
Power
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
MED LOW DEFROST
approx.
50% of
Full Power
. . . . . . . . . . . . . . . . . . . . . . . . . .
LOW
approx. 30% of Full Power
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . approx. 10% of
INSTANT COOK/START COOKING
Full Power
AUTO START COOKING
EASY DEFROST, AUTO COOK
EASY REHEAT
MORE/LESS pad
I
a- c .
1 Approx. 1 1.3 kg
e
--
(HD44101U
NOTE:
Numbers and leters shown after sentences such as “RD44101 U” are for factory use only.
2
R-4A20
R4A30
1.
Ventilation
openings
7. Door latches
2.
Oven lamp
8.
Door button open
3. Oven door with see through window
9. Touch Control Panel
4.
Removable
turntable
10.
Digital readout
5. Roller Stay
11.
Waveguide cover
6. Hinges
12. Access cover for oven lamp replacement
Touch Control Panel
AUTO COOK MENUS
AUTO COOK
Touch to select Auto Cook mode.
EASY REHEAT PAD
Touch to select Easy Reheat mode. L
EASY REHEAT MENUS
EASY DEFROST PAD
Touch to defrost meat by entering weight.
NUMBER PADS
Touch to enter cooking times, clock time, weight or quantity
of food, or to select the Auto Cook or Easy Reheat menus.
- STOP/CLEAR PAD
Touch to erase during programming.
Touch once to stop operation of oven during cooking; touch
twice to cancel cooking programme.
r
AUTO START/CLOCK PAD
Touch to set clock or Auto Start time.
r
VARIABLE COOKING CONTROL PADS
Touch to select microwave power setting.
If not touched, HIGH is automatically selected.
MORE(A), LESS(r) PADS
Touch to increase/decrease the time in one minute increments
during cooking or to increase/decrease the time whilst
programming the Easy Reheat, Auto Cook or Easy Defrost
modes.
- 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.
I
MEMORY
Touch to enter one frequently used cooking programme.
Touch to recall the memorized programme.
R4AlO
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OPERATION
DESCRIPTION OF OPERATING SEQUENCE
The following is a description of component functions
during oven operation.
(RD71101 U)
OFF CONDITION
Closing the door activates both door latch switches:
upper latch switch and lower latch switch. (in this
condition, the monitor switch contacts are opened.)
The stop switch is activated by the latch head.
When oven is plugged in, 240 volts A.C. is supplied to
the control unit.
But no components in the oven will operate.(Figure
o-1 .)
Note: When the door is opened by pushing the door
open button, the contacts of the relay RY-1 are
1.
closed, then the oven lamp lights.
The display will show flashing “88:88”.
To set any program or set the clock, you must
first touch the STOP/CLEAR pad.
The display will clear, and I:00 will appear and
count up every minute.
COOKING CONDITION
HIGH COOKING CONDITION
Program desired cooking time and Variable Cooking
Control by touching the NUMBER pads and the HIGH
pad of the Variable Cooking Control. When the START
pad is touched, the following operations occur:
1.
2.
3.
4.
5.
The contacts of relays ‘are closed and components
connected to the relays are turned on as follows.
(For details, refer to Figure O-2)
RELAY
CONNECTED COMPONENTS
RY-1
Oven h-np/turntable motor/fan motor
RY-2
power transformer
240 volts A.C. is supplied to the primary winding
of the power transformer and is converted to about
3.5 volts A.C. output on the filament winding, and
approximately 1900 volts A.C. on the high voltage
winding.
The filament winding voltage heats the magnetron
filament and the H.V.
voltage doubler circuit.
winding
voltage is sent to a
The microwave energy produced by the magnetron
is channeled through the waveguide into the cavity
feed-box, and then into the cavity where the food
is placed to be cooked.
Upon completion of the cooking time, the power
transformer, oven lamp, etc. are turned off, and the
generation of microwave energy is stopped.
oven will revert to the OFF condition.
The
6. When the door is opened during a cook cycle,
monitor switch, upper latch switch and lower latch
switch are activated with the following results. The
circuits to the turntable motor, the cooling fan motor, and the high voltage components are deenergized, the oven lamp remains on, and the digital
readout displays the time still remaining in the cook
cycle when the door was opened.
7. The monitor switch is electrically monitoring the
operation of the upper latch switch and is mechanically associated with the door so that it will func-
tion in the followina sequence.
(U
(2)
When the door opens from a closed position
the stop switch, upper and lower latch switches
first operate to open their contacts, and then
the monitor switch contacts close.
When the door is closed from the open position, the monitor switch contacts first open,
and then the contacts of the stop switch, upper
and lower latch switches close.
In case the upper latch switch fails with its contacts
closed when the door is opened, the monitor switch
will form a short circuit through the monitor fuse, and
the upper latch switch, causing the monitor fuse to
blow.
MED HIGH, MED, MED LOW/DEFROST, LOW
COOKING
When Variable Cooking Power is programed, the 240
volts A.C. is supplied to the power transformer
intermittently through the contacts of relay( RY -2)
which is operated by the control unit within a 30 second time base. Microwave power operation is as follows:
VARI-MODE
HIGH
(100% power)
MED HIGH
(approx. 70%‘power)
MED
(approx. 50% power)
MED LOW/DEFROST
ON TIME
32 sec.
24 sec.
18 sec.
OFF TIME
0 sec.
8 sec.
14 sec.
(approx. 30% power)
LOW
(approx. 10% power)
12 sec.
6 sec.
20 sec.
26 sec.
Note: The ON/OFF time ratio does not correspond
with the percentage of microwave power, because approx. 2 seconds are needed for heating
of the magnetron filament.
(RD71401 U)
4
J-4
240V-50Hz
A-L
240V--5OHz
vl
SCHEMATIC
NOTE CONDITION OF OVEN
1 DOOR CLOSED
2 CLOCK APPEARS
ON DISPLAY
Fuss
MS.3A
SWITCH
TURNTABLE MOTOR
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I a-T
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M v RECTIFIER
L------A
MAGNETRON .
SCHEMATIC
I I
CONTROL HIGH
4 START PAD
TOUCHED
NOTE: CONDITION OF OVEf
1 DOOR CLOSED
2 COOKING TIME
PROGRAMMED
3 VARIABLE COOKING
I I s-a I -
1 k&i~ 1 UNIT
CONTROL
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45-
83
e-v
h-
,
M V RECTIFIER
Lam-’
MAGNETRON N
I
Figure. 0- 1, Oven Schematic-Off Condition
Figure. O-2. Oven Schematic-Cooking Condition
4
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R.4A30
DESCRIPTION AND FUNCTION OF COMPONENTS
UPPER LATCH SWITCH
The switch is activated by the upper latch head on the
door while the door is closed.
When the door is opened, the switch interrupts the
circuit (except oven lamp).
LOWER LATCH SWITCH
The switch is activated by the lower latch head on the
door. When the door is opened, the switch interrupts
the circuit to transformer.
A cook cycle cannot take
place until the door is firmly closed and the INSTANT
COOK/START pad touched.
STOP SWITCH
The stop switch is located on latch hook and activated
by the lower latch head and switch lever. When the
open button is depressed while the oven is in cook
cycle, the stop switch contacts open to de-energize the
reiay( RY-1) and reiay( RY-2) circuits in the control and
causes cook time count down to pause.
MONITOR SWITCH
The monitor switch is activated (the contacts of “NC”
opened) by the upper latch head on the door while the
door is closed. The switch is intended to render the
oven inoperative by means of blowning the monitor
fuse when the contacts of the upper latch switch fail
to open when the door is opened.
Functions:
1. When the door is opened, the monitor switch
normal close contacts (to the ON condition) due
to their being normally closed. At this time the
upper latch switch is in the OFF condition (contacts open) due to their being normally open contact switch.
2. As the door goes to a closed position, the monitor
switch normal close contacts are first opened and
then the upper latch switch contacts close and
lower latch switch contacts, (On opening the door,
each of these switches operate inversely.)
3. if the door is opened, and the upper latch switch
contacts fail to open, the monitor fuse blows simultaneously with closing of the monitor switch
contacts.
CAUTiON:BEFORE REPLACING A BLOWN MONI-
TOR FUSE, TEST THE UPPER LATCH FOR
PROPER OPERATION. (REFER TO CHAPTER “TEST PROCEDURE”).
DOOR OPEN MECHANISM
The door can be opened by pushing the open button
on the control panel, refer to the Figure D-l.
When the open button is pushed, the cook switch lever
on the latch hook 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.
OVEN LAMP
The oven lamp illuminates the interior of the oven so
that food being cooked can be examined visually
through the door window without having to open the
door.
COOLING FAN MOTOR
The cooling fan motor drives a blade which draws
cooling air through the back vents.
This cooling 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 vaports given off from the heating foods.
it is then exhausted at the back of the oven cavity.
MAGNETRON TEMP. FUSE
The temp. fuse located on the oven cavity is designed
to prevent damage to the magnetron if an overheated
condition develops in the tube due to cooling fan failure, obstructed air ducts, dirty or blocked air intake, etc.
Under normal operation, the temp. fuse remains closed.
However, when abnormally high temperatures are
reached within the magnetron, the fuse will open,
causing the oven to shut down.
This is a fuse and it does not reset.
OVEN TEMP. FUSE
When foods in oven cavity fire, oven temperature fuse
stops ventilating from fan motor and extinguishes fire
in oven cavity before fire goes outside the unit.
\
\
/
\
0
. MONITOR
SWITCH
UPPER
LATCH
SWITCH
OPEN
BUTTON
Figure D-1. Latch Switches Adjustment
SERVICING
TROUBLESHOOTING GUIDE
MIA10 iE2::
When troubleshooting the microwave oven, it is helpful to
follow the Sequence of Operation in performing 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 Procedures section.”
IMPORTANT: If the oven becomes inoperative because of a
blown fuse in the monitor-upper latch switch
circuit, check the monitor switch and upper
latch switch before replacing the fuse.
PROBLEM
I
POSSIBLE CAUSE
TEST PROCEDURE OR
CORRECTION
l
OFF CONDITION
f
Home fuse blows when power cord
is plugged into wall receptacle.
Shorted wire in power cord or wire harness.
Replace cord or check wiring.
Oven fuse blows when power cord
Shorted wire harness. Check and repair wire harness.
is plugged into wall receptacle.
” 88:88 ” does not appear in display
when power cord is first plugged
into wall outlet.
Defective monitor switch.
NO power at outlet.
No power from service entrance.
Procedure G.
Check home fuse.
Check wall outlet.
I
Open wire in power cord or wire harness.
I
Replace same or repair wiring.
I
I
Blown fuse.
I
Procedure H.
I
I
Defective temp. fuse.
I
Procedure F.
(magnetron and oven)
I
/
Open wire In power cord, wlrrng harness, Replace or reparr wrring.
or wrring between control panel assembly
unrts.
I
Defective control unit.
I
Procedure I.
I
I
1
1
Display does not operate properly
Defective stop swrtch.
Procedure E.
when STOP/CLEAR key is touched,
b
(Buzzer should sound and time of
Defective control unit.
Procedure I.
day should appear in display.)
Oven lamp does not light with
door opened.
Defective oven lamp.
Defective stop switch.
Replace oven lamp.
Procedure E.
Defective control unit,
Open or loose wire connection to the above
components.
Procedure I.
Check wiring.
COOKING CONDITION
Oven lamp does not light in cook
cycle.
Defective relay Fly-1 on control unit.
Procedure I.
(Do light when door is opened.)
7
R4AlO
R4A20
R4A30
TROUBLESHOOTING GUIDE (CONT’D)
PROBLEM
1
POSSIBLE CAUSE
TEST PROCEDURE OR
CORRECTION
4
COOKING CONDITION (CONT’D)
Oven lamp does not light at ail.
I
Burned out bulb.
I
Replace oven lamp.
1
I
Open wiring to oven lamp socket.
I
Check and repair wiring.
-1
Cook indicator appears in display but
turntaMe motor does not operate.
Defective relay RY-1 on control unit.
Turntable motor defective.
Open or loose wiring between control
unit and motor.
Procedure I.
Replace motor.
Check and repair wiring.
Oven lamp lights but fan motor
does not operate.
(Turntable motor does operate)
Defective fan motor,
Replace fan moter.
Open or loose wiring to fan motor. Check and repair wiring.
Oven does not go into cook cycle
when INSTANT COOK/START
key is touched.
Upper and Lower latch switches and stop
switch defective or out of adjustment.
Blown fuse.
Procedure E.
Procedure H.
I
Defective temp. fuse. (Magnetron and Oven) 1 Procedure F.
-1
Defective relay RY-1, RY-2 on control unit.
Open or loose wiring to the above
components.
Procedure I.
Check and repair wiring.
i
Oven seems to be operating but
little or no heat is produced in
oven load. (Food incompletely
cooked or not cooked at all at end
Defective magnetron.
Defective relay RY-2 on control unit.
Procedure A.
Procedure I.
of cook cycle)
I
Defective power transformer.
I
Procedure B.
F
Defective rectifier.
Procedure C.
Defective high voltage capacitor.
Procedure 0.
Oven goes into a cook cycle but
extremely uneven heating is
produced in oven load (food).
,
Defective control unit.
Procedure I.
Open or loose wiring to the above
components.
Check and repair wiring.
Turntable motor does not operate.
Replace turntable motor.
3ven does not cook properly when
:ooking control set to LOW, ME0
LOW, MED, MED HIGH cooking
lowers.
Operates properly on HIGH.)
Defective control unit.
Open or loose wiring between the above
components.
Procedure I.
Check and repair wiring.
8
R4AlO
EE:
PROBLEM
POSSIBLE CAUSE
TEST PROCEDURE OR
CORRECTION
EASY DEFROST condition touching
INSTANT COOK/START Pad,
“ERROR” appears.
Programmed incorrectly
EASY DEFROST will only operate
on a specificweight.
Range for each food category.
See steps for Easy Defrost is
Operation Manual.
Defective control unit.
Procedure I -
9
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