WH5.5
R-4X55
ls4x55a
SHARP SERVICE MANUAL
S9312R4X55PJZ
MICROWAVE OVEN
R-4H55
MODELS Rm4H55
R-4X55
Rm4X55B
In interests of user-safety the oven should be restored to its original condi-
tion and only parts identical to those specified should be used.
TABLE OF CONTENTS
GENERAL IMPORTANT INFORMATION
we
......................................................................................................
WARNING
......................................................................................................................................................
.
RODUCT SPECIFICATIONS
.........................................................................................................................
2
APPEARANCE VIEW
....................................................................................................................................
3
OPERATING SEQUENCE
.............................................................................................................................
FUNCTION OF
IMPORTANT COMPONENTS’
............................................................................................
.;
TRABLESHOOTING CHART ......................................................................................................................... 7
TEST PROCEDURE ....................................................................................................................................
10
TOUCH CONTROL PANEL
........................................................................................................................
.20
COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE
.......................................................
.27
MICROWAVE MEASUREMENT
.................................................................................................................
.30
WIRING DIAGRAM
......................................................................................................................................
34
PICTORIAL DIAGRAM
...............................................................................................................................
.36
CONTROL PANEL CIRCUIT
......................................................................................................................
.38
PRINTED WIRING BOAD
............................................................................................................................
40
PARTS LIST ............
. ...................................................................................................................................
41
SHARP CORPORATION
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R-4X55B
R-4X55
SERVICE MANUAL
SHARP
MICROWAVE OVEN
R-4H55 /R-4X55/ Fb4X55B
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 that they will be qualified to render satisfactory customer service.
CAUTION
MICROWAVE RADIATION
Service engineers 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
andgaskets must be secured. Never operate the device without
a microwave energy absorbing load attached. Never look into
an open waveguide.
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 CORPORATlON
OSAKA, JAPAN
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_I’ MICROWAVE MESUREMENT
WIRING DIAGRAMS
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PARTS LIST
._ .
R-4X55
A-4X55B
PRODUCT SPECIFICATIONS
ITEM
Power Requirements
Power Consumption
Power Output
Case Dimensions
Cooking Cavity Dimensions
Turntable diameter
Control Complement
Set Weight
DESCRIPTION
240 Volts (Australia) / 230 - 240 Volts (New Zealand)
50 Hertz
Single phase, 3 wire earthed
1.4 kW
750 watts nominal of RF microwave energy (AS 2895 1986)
850 watts nominal of RF microwave energy (IEC-705-1988 )
Operating frequency of 2450MHz
Width 550mm
Height 312mm
Depth 420mm
Width 381 mm
Height 21 Omm
Depth 411 mm
360mm
Touch Control System
Clock ( 1:OO - 12:59)
Timer (0 - 99 minutes 99 secinds)
Microwave Power for Variable Cooking
Repetition Rate;
HIGH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Full power throughout the cooking time
MEDIUM HIGH
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . approx. 70% of Full Power
MEDIUM
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . approx. 50% of Full Power
MEDIUM LOW
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . approx. 30% of Full Power
LOW
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . approx. 10% of Full Power
DEFROST SENSOR (R-4X55/4X55B)
WEIGHT ADJUST (R-4X55/4X55B)
EASY DEFROST (R-4H55)
SENSOR INSTANT ACTION
SENSOR COOK, REHEAT SENSOR
NUMBER pads
POWER LEVEL pad, MORE, LESS pads
STOP/CLEAR pad
AUTO START/CLOCK pad
INSTANT COOK/START pad
Approx. 17 kg
GENERAL INFORMATlOil
WARNING
THIS APPLIANCE 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
2
R-4H55
R-4X55
WX55B
APPEARANCE VIEW
1.
!1
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Ventilation openings
Oven lamp
Door hinges
Safety door latches
See through door
Coupling
Door open button
Touch control panel
Digital readout
Wave guide cover
Access cover for oven
I
lamp replacement
12. Power supply cord
13.Menu Label for Sensor
Cook
14. Rating label
15. Defrost rack(R-4X55/B)
TOUCH CONTROL PANEL
I
m SMART
I & EASY
R-4H55
a. SENSOR COOK PAD
Press to select several popular menus.
b. REHEAT SENSOR PAD
Press to select 3 popular Reheat menus.
c. WEIGHT ADJUST PAD (R-4X55, R-4X55B)
Press to zero the weight of your own dishes before
defrosting on DEFROST SENSOR.
d. DEFROST SENSOR PAD (R-4X55, R-4X55B)
Press to defrost meat or seafood automatically.
e. SENSOR INSTANT ACTION PADS
Press to once to cook 1 of 6 popular menus.
f. NUMBER PAD
Press to enter cooking times, clock time or to select
the Sensor Cook menus.
g. POWER LEVEL PAD
Press to select microwave power setting
If not pressed, HIGH is automatically selected.
5
2 3 4 5
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L-6 7 8 9 0
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h. EASY DEFROST PAD (R-4H55)
Press to defrost meat by entering weight.
i.
MORE( A ), LESS( v ) PADS
Press to increase/decrease the time in one minute increments during
cooking or to alter the doneness for the Sensor Instant Action, Reheat
Sensor, Sensor Cook, Easy Defrost(R-4H55) or Defrost Sensor (R4X55/4X558) modes.
j. STOP/CLEAR PAD
Press to clear during programming.
Press once to stop operation of oven during cooking: press twice to
cancel cooking programme.
k. AUTO START/CLOCK PAD
Press to set clock or Auto Start time.
I. INSTANT COOK/START PAD
Press once to cook for 1 minute at HIGH or increase by 1 minute multiples each time this pad is pressed during cooking.
Press to start oven after setting programmes.
3
R-IX55
R-4X558
OPERATION SEQUENCE
OFF CONDITION
Closing the door activates all door interlock switches
(Upper latch switch, Lower 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 is supplied to the point (A3+A5) in the control unit.
Figure O-1 on page 34 or 35
1. The display flashes “88:88”.
2. To set any programmes or set the clock, you must first
touch the STOP/CLEAR pad.
3. .I’ :
” 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
pads and start the oven with touching START pad.
Function sequence
Figure O-2 on page 34 or 35
CONNECTED COMPONENTS
RELAY
Oven lamp, Fan motor, Turntable motor
RYl
Power transformer
RY2
1.
2.
3.
4.
5.
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.
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..
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
SWITCH
DURING
DOOR OPEN
CONTACT
COOKING (NO COOKING)
Upper latch switch
COM-NO
Closed Open
Lower latch switch
COM-NO
Closed Open
Monitor switch
COM-NC
Open Closed
Stop switch
COM-NO
Closed
open
The circuits to the power transformer, fan motor and
turntable motor are cut off when the upper latch switch,
lower 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 interrupted, because
the relay (RYl) stays closed. Shown in the display is
the remaining time.
6. MONITOR SWITCH CIRCUIT
The monitor switch is mechanically controlled by oven
door, and monitors the operation of the upper and lower
latch switches.
6-l
6-2.
6-3.
When the oven door is opened during or after the
cycle of a cooking program, the upper latch switch,
lower latch switch and stop switch must open their
contacts first.
After that the contacts (COM-NC) of the monitor
switch can be closed.
When the oven door is closed, the contacts (COM-
NC) of the monitor switch must be opened. After that
the contacts of the upper latch switch, lower latch
switch and stop switch are closed.
When the oven door is opened and the contacts of
theupper latch switch, lower latch switch remain
closed. The fuse M8A will blow, because the monitor
switch is closed and a short circuit is caused.
VARIABLE COOKING
When the microwave oven is preset for variable cooking
power. Rated voltage is supplied to the power transformer
intermittently within a 32-second time base through the
relay contact which is coupled with the relay(RY2). The following levels of microwave power are given.
SETTING;
HIGH
32 sec. ON
MEDIUM HIGH 24 sec. ON
8 sec. OFF
Approx. 70%
MEDIUM
MEDIUM LOW
LOW
I
18 sec. ON 14 sec. OFF
Approx. 50%
12 sec. ON
20 sec. OFF
Approx. 30%
6 sec. ON 26 sec. OFF
Approx. 10%
1
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.
4
SENSOR COOKING CONDITION
Using the SENSOR COOK, REHEAT SENSOR or SENSOR INSTANT ACTION function, the foods are cooked or
defrosted without figuring time, power level or quantity.
When the oven senses enough steam from the food, it re-
lays the information to its microprocessor which will calcu-
late the remaining cooking time and power level needed
for best results.
When the food is cooked, water vapor is developed. The
sensor “senses” the vapor and its resistance increases
gradually. When the resistance reaches the value set according to the menu, supplementary cooking is started.
The time of supplementary cooking is determined by experiment with each food category and inputted into the LSI.
An example of how sensor works:
1. Potatoes at room temperature. Vapor is emitted very
slowly.
2. Heat potatoes. Moisture and humidity is emitted rapidly. You can smell the aroma as it cooks.
Cooking Sequence.
1. Touch each SENSOR COOK function pad to operating
the sensor cooking.
NOTE:The oven should not be onerated on SENSOR
COOK, REHEAT SENSOR or SENSOR INSTANT
ACTION immediately after plugging in the unit.
Wait five minutes before cooking on SENSOR
COOK, REHEAT SENSOR or SENSOR INSTANT
ACTION.
2.
3.
4.
Select desired Sensor setting.
Touch START pad (REHEAT SENSOR and SENSOR
INSTANT ACTION fuction are not neccessary to touch
START pad.) The coil of shut-off relay (RY-1) is energized, the turntable motor, oven lamp and cooling fan
motor are turned on, but the power transformer is not
turned on.
After about 16 seconds, the cook relay (RY-2) is energized. The power transformer is turned on, microwave
energy is produced and first stage is started.
The 16 seconds is the cooling time required to remove
any vapor from the oven cavity and sensor.
NOTE:During this first stage, do not open the door or touch
5.
6.
7.
STOP/CLEAR pad
When the sensor detects the vapor emitted from the
food, the display switches over to the remaining cooking time and the timer counts down to zero.
At this time, the door may be opened to stir food, turn it
or season, etc.
When the timer reaches zero, an audible signal
sounds. The shut-off relay and cook relay are de-energized and the power transformer, oven lamp, etc. are
turned off.
Opening the door or touching the STOP/CLEAR pad,
the time of day will reappear on the display and the
oven will revert to an OFF condition.
3. Sensor detects moisture and humidity and calculates
cooking time and variable power.
5
R4H55
R-4X55
R-4X55B
FUNCTION OF IMPORTANT COMPONENTS
DOOR OPEN MECHANISM
The door can be opened by pushing the door open button
an the control panel. When the door open button is
pushed, the latch 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.
LATCH
MONITOR
HOOK \
, SWITCH
UPPER
LATCH
SWITCH
LATCH
HEAD
DOOR
OPEN ’
BUTTON
Figure D-l. Door Open Mechanism
UPPER LATCH SWITCH, LOWER LATCH
SWITCH AND STOP SWITCH
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
1. When the oven door is closed, the contacts (COM- NC)
must be opened.
2. When the oven door is opened, the contacts (COMNC) must be closed.
3. If the oven door is opened and the contacts (COM- NO)
of the upper and lower latch switches fail to open, the
fuse (M8A) blows simultaneously with closing the contacts (COM-NC) of the monitor switch.
CAUTION: BEFORE REPLACING A BLOWN FUSE
(M8A) TEST THE UPPER AND LOWER
LATCH SWITCHES, MONITOR SWITCH
AND MONITOR RESISTOR FOR PROPER
OPERATION. (REFER TO CHAPTER “TEST
PROCEDURE”.)
MONITOR RESISTOR (0.8$2 20W)
The monitor resistor prevents the fuse (M8A) bursting
when the fuse blows due to the 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
temperature rise of the power transformer by blowing the
fuse (M8A) when the high voltage rectifier is shorted.
/
H;;jH VOLTAGE RECTIFIER
The rated peak reverse voltage of Di 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 asymmet-
ric 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
M8A.)
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 8A flow through the
primary winding of the power transformer.
6. The fuse (M8A) blows by the large electric currents.
7. The power supply to the power transformer is cut off.
THERMAL CUT-OUT 145°C (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. However, when abnormally high temperatures are reached
within the oven cavity, the oven thermal cut-out will open at
145”C, causing the oven to shut down. The thermal cut-out
will be close its contacts again when its temperature goes
down lower than -20°C.
FUSE (M8A)
1. If the wire harness or electrical components are shortcircuited, this fuse blows to prevent an electric shock or
fire hazard;’
2. The fuse blows when the asymmetric rectifier, H.V.
rectifier, H.V. wire harness, H.V. capacitor, magnetron
or secondary winding of power transformer is shorted.
3. The fuse also blows when upper and lower latch
switches remains closed with the oven door open and
when the monitor switch closes.
TEMPERATURE FUSE 15O’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
puts the oven out of operation.
The defective fuse must be replaced with new rated one.
6
RdX55
RdX55B
TURNTABLE MOTOR
The turntable motor drives the turntable roller assembly to
neled through the oven cavity to remove steam and vapors
given off from the heating foods. It is then exhausted
rotate the turntable.
through the exhausting air vents at the oven cavity.
FAN MOTOR
The fan motor drives a blade which draws external cool air.
NOISE FILTER (For New Zealand Model R-4X55)
The noise filter prevents the radio frequency interference
This cool air is directed through the air vanes surrounding
that might flow back in the power circuit.
the magnetron and cools the magnetron. This air is chan-
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
REMEMBER TO CHECK*
1) Disconnect the supply.
2) Door opened, and wedged open.
3) Discharge high voltage capacitor.
1) Reconnect all leads removed from components during testing.
2) Replace the outer case (cabinet).
3) Reconnect the supply.
WARNING AGAINST THE CHARGE OF THE 4) Run the oven. Check all functions.
HIGH-VOLTAGE CAPACITOR
The high-voltage capacitor remains charged about
Microwave ovens should not be run empty. To test for
60 seconds after the oven has been switched off.
the presence of microwave energy within a cavity,
Wait for 60 seconds and then short-circuit the con-
place a cup of cold water on the oven turntable, close
nection of the high-voltage capacitor (that is, of the
the door and set the microwave timer for two (2) min-
connecting lead of the high-voltage rectifier) against
utes. Set the power level to HIGH and push the START
the chassis with the use of an insulated screwdriver.
button. When the two minutes has elapsed (timer at
zero) carefully check that the water is now hot. If the
Sharp recommend that wherever possible fault-finding
water remains cold carry out 3D checks and re-exam-
is carried out with the supply disconnected. It may in,
ine the connections to the component being tested.
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 pri-
mary 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 of the power transformer.
When all service work is completed, and the oven is fully assembled, the microwave power output should be
checked and microwave reakage test carried out
TROUBLESHOOTING GUIDE
When troubleshooting the microwave oven, it is helpful
IMPORTANT: If the oven becomes inoperative because of a
to follow the Sequence of Operation in performing the
blown fuse M8A in the upper latch switch -
checks. Many of the possible causes of trouble will re-
lower latch switch - monitor switch - monitor
quire that a specific test be per-formed. These tests are
resistor circuit, check the upper latch switch,
given a procedure letter which will be found in the “Test
lower latch switch, monitor switch and moni-
Proceduresection.
tor resistor before replacing the fuse M8A.
7
TEST PROCEDURE
ABCDEEEEFGHHII
J K L t 0
Ii
POSSIBLE CASE
:
AND DEFECTIVE
L2
:ONDITION
PROBLEM
Home fuse blows when power supply
cord is plugged into wall outlet.
FUSE M8A blows when power supply
.cord is plugged into wall outlet.
“88:88” does not appear in display but
power supply cord is plugged into wall
outlet.
0
00
00
0 00 00 0
Display does not operate properly
&orrro~ when STOP/CLEAR pad is touched.
Oven lamp does not light at door
opened. (Display appears.)
Oven does not start when the 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 any electrical parts does not
stop when cooking time is 0 or STOP/
CLEAR pad is touched.
Oven seems to be operating but little
0
0
0
00
00
00
0
0
0
0
00
or no heat is produced in oven load. 0 0 0 0
Ly:;rwave power level is set at
0
00
OOKMG Oven does not seems to be operating
roperly when MEDIUM HIGH ME-
oNDrTtoN EIUM, MEDIUM LOW or LOW i’s set.
(Oven operates roper1 at HIGH and
then the ST 8 I! P/CL AR
touched the oven stops.)
pad is
00
Oven goes into cook cycle but shuts
down before end of cooking cycle.
000
0
Oven stops as soon as when the 0 0 0 0
START pad is touched.
0
in
#ENSOR
AH sensor does not end 1st stage or
iEiyr&
cooking during Sensor Cooking condition (Oven does not shut off when a
cup of water is boiling by Sensor
0
0
Cooking.) or oven stops soon.
‘EIGHT
ENSOR
The display shows “ERROR” and
oND,T,ON oven stops during Defrost Sensor
Cooking condition
8
. .--
R-4X55
R-4X55B
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RdH55
RdX55
RdX55B
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 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 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 (1 Litre water load)
The following test procedure should be carried out with the microwaveoven 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 calorie and watt is
used.When P(W) heating works for t(second), approximately P x t/4.1 87calorie 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 thewater is V x AT
The formula is as follows;
Pxtl4.187=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 . . . . . . . . . . . . . . . . . . . . . 47
sec.
P=90xAT
Measuring condition:
1. Container
The water container must be a cylindrical borosilicate glass vessel having a maximum material
thickness of 3 mm and an outside diameter of approximately 190 mm.
2. Temperature of the oven and vessel
The oven and the empty vessel are at ambient temperature prior to the start of the test.
3. Temperature of the water
The initial temperature of the water is (10 f. 2)X.
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 heatup time is not included.
NOTE: The operation time of the microwave oven is “t + 2" sec. 2 sec. is magnetron filament heat-up
time.
Measuring method:
1. Measure the initial temperature of the water before the water is added to the vessel.
(Example: The initial temperature Tl = 11 “C)
2. Add the 1 litre water to the vessel.
3
Place the load on the centre of the shelf.
10
TEST PROCEDURES
PROCEDURE
LETTER
COMPONENT TEST
4. Operate the microwave oven at HIGH for the temperature of the water rises by a value A T of
(10 -t 2)“C.
5. Stir the water to equalize temperature throughout the vessel.
6. Measure the final water temperature.
(Example: The final temperature T2 = 21 “C)
7. Calculate the microwave power output P in watts from above formula.
Initial temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tl
= 11 ‘C
Temperature after
(47+2)= 49
sec. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . T2
= 21 “C
Temperature difference
Cold-Warm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
AT1 = 10°C
Measured output power
The equation
is ‘!P= 90 x AT"
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . P= 90 x 10°C = 900 Watts
JUDGMENT: The measured output power should be at least + 15 % of the rated output
power.
CAUTION: 1 C CORRESPONDS TO 90 WATTS. REPEAT MEASUREMENT IF THE POWER IS
INSUFFICIENT.
l5d
Heat up for 49 sec.
MICROWAVE OUTPUT POWER (2 Litre water load)
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.
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 formulae is as follows;
P =8330xAT/t
Our condition for the water load is as follows:
Room temperature . . . . . . . . . . . . . . ...23+ 2°C
Power supply Voltage
. . . . . . . . . . . . . . . . . . Rated
voltage.
Water load . . . . ...2000 ml
Initial temperature
. . . . . . . 23 & 1 “C
Heating time .,.. 1 min. 51 sec.
P=75xAT
Measuring method:
A) The two water containers must be prepared.
The water container must be one (1) litre beaker made of Pyrex glass and its diameter approximately 12cm.
B) Put the one (1) litre water into each beaker (Each beaker has one litre water). The initial tempera-
ture of the water should be 23-C.
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 (2) beakers as touching each other in the centre of the oven cavity.
E) Set the timer to 1 minute and 51 seconds and then start the oven at HIGH.
11
TEST PROCEDURES
PROCEDURE
LETTER
COMPONENT TEST
F) The time must be measured with stopwatch or wristwatch.
G) After 1 minute and 51 seconds, stop the oven by opening the door.
H) Put the two (2) beakers out of the oven cavity and measure the temperature of the water by stirring
the water with thermometer and note them.
Example
Initial temperature . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Tl = 23°C T2 = 24°C
Temperature after 1 min. 51 sec.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Tl = 33°C T2 = 34°C
Temperature difference Cold-Warm
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
AT1 = 10°C AT2 = 10°C
Mean temperature
rise AT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
AT = (AT1 rt AT2) / 2 = (1 O”C+lO”C) / 2 = 10°C
Measured output power
The equation is P= 75 x AT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . P= 75 x
10°C = 750 Watts
NOTE: The measured output power should be at least f 15 % of the rated output power.
CAUTION: 1°C CORRESPONDS TO 75 WATTS.
REPEAT MEASUREMENT IF THE POWER IS INSUFFICIENT.
(Tl ‘C)
(T2’C) (Tl ‘C)
Heat up for 1 min. 51 set
II
Pii
2 -
- -
- -
- -
(T2’C)
B
POWER TRANSFORMER TEST
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 measurements at the highvoltage 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
. . . . . . . . . . . . . . . . . . . . . . . . . approximately
1 .42 ohms.
b. Secondary winding
. . . . . . . . . . . . . . . . . . . . . approximately
78.9ohms.
c. Filament winding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
less than 1 ohm.
lf the reading obtained are not as stated above, then the power transformer is probably faulty and
should be replaced.
CARRY OUT $FJ CHECKS
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.
12
R-4H55
R-4X55
R-4X55B
TEST PROCEDURES
PROCEDURE
LETTER
COMPONENT TEST
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 infinite in
one direction and mor than 100 kR in the other direction.
CARRY OUT* CHECKS
ASYMMETRIC RECTIFIER TEST
ASYMMETRIC
CARRY OUT 3D CHECKS.
RECTIFIER
Isolate the high voltage rectifier assembly from the HV circuit. The asymmetric rectifier can be tested
using an ohmmeter se? 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 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 filament winding of the power trans-
former 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.
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 resis-
tance range.
C. A normal capacitor shows continuity for a short time (kick) and then a resistance of about 10 MR
after it has been charged.
D. A short-circuited capacitor shows continuity all the time.
E. An open capacitor constantly shows a resistance of about 10 MR 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 inifinte when the capacitor is nor-
mal.
If incorrect readings are obtained, the high voltage capacitor must be replaced.
CARRY OUT $FJ CHECKS
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
Plunger Operation
COM to NO COM to NC
Released
O.C. S.C.
Depressed
S.C.
O.C.
COM; Common terminal
NO; Normally open terminal
NC; Normally closed terminal
S.C.; Short circuit
O.C.; Open circuit
I
If incorrect readings are obtained, make the necessary switch adjustment or replace the switch.
CARRY OUT 4R CHECKS.
13
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