Sharp R872M-006 Schematic
SERVICE MANUAL
MICROWAVE OVEN WITH
GRILL AND CONVECTION
SERVICING
PRODUCT SPECIFICATIONS
R-872(W)M/ R-872(SL)M
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.
WARNING
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 energized.
WARNING
Never operate the oven until the following points are ensured.
(A) The door is tightly closed.
(B) The door brackets and hinges are not defective.
(C) The door packing is not damaged.
(D) The door is not deformed or warped.
(E) There is not any other visible damage with the oven.
Servicing and repair work must be carried out only by trained
service engineers.
GENERAL INFORMATION
APPEARANCE VIEW
OPERATING SEQUENCE
FUNCTION OF IMPORTANT
COMPONENTS
TROUBLESHOOTING GUIDE
AND TEST PROCEDURE
TOUCH CONTROL PANEL
COMPONENT REPLACEMENT
AND ADJUSTMENT PROCEDURE
MICROWAVE MEASUREMENT
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.
All the parts marked “∆” on parts list may cause undue microwave
exposure, by themselves, or when they are damaged, loosened or
removed.
Never operate the Grill and/ or Bottom heater with the oven
outer cabinet removed. (Because air flow is eliminated, and the
excess heat generated on adjacent components). It can cause
permanent damage or a fire.
SHARP CORPORATION
OSAKA, JAPAN
R-872M - 1
WIRING DIAGRAM
PARTS LIST
SERVICING
WARNING TO SERVICE PERSONNEL
Microwave ovens contain circuitry capable of producing very high voltage and current, contact with following parts will
result in electrocution.
High voltage capacitor, High voltage transformer, Magnetron, High voltage rectifier assembly, High voltage harness.
REMEMBER TO CHECK 3D
1) Disconnect the supply.
2) Door opened, and wedged open.
3) Discharge high voltage capacitor.
WARNING: AGAINST THE CHARGE OF THE HIGH-
VOLTAGE CAPACITOR
The high-voltage capacitor remains charged about 60 seconds after the oven has been switched off. Wait for 60
seconds and then short-circuit the connection of the highvoltage capacitor (that is, of the connecting lead of the highvoltage rectifier) against the chassis with the use of an
insulated screwdriver.
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
then disconnect the leads to the primary of the High voltage
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 High
voltage transformer.
3D checks and
REMEMBER TO CHECK 4R
1) Reconnect all leads removed from components during
testing.
2) Replace the outer case (cabinet).
3) Reconnect the supply.
4) Run the oven. Check all functions.
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
power to HIGH and set the microwave timer for two (2) minutes.
When the two minutes has elapsed (timer at zero) carefully
check that the water is now hot. If the water remains cold carry
3D checks and re-examine the connections to the compo-
out
nent being tested.
When all service work is completed, and the oven is fully
assembled, the microwave power output should be checked and
a microwave leakage test should be carried out.
R-872M - 2
PRODUCT DESCRIPTION
SPECIFICATION
ITEM DESCRIPTION
Power Requirements 230 - 240 Volts / 50 Hertz / Single phase, 3 wire earthed
Power Consumption Microwave cooking 1 .45kW Approx. 6.2 A
Convection cooking 1.53 kW Approx. 6.6 A
Top Grill mode ...................... 1.05 kW Approx. 4.2 A
Grill cooking Bottom Grill mode................. 0.55 kW Approx. 2.2 A
Top and Bottom mode ......... 1.55 kW Approx. 6.3 A
Micro and Top Grill ................. 2.4 kW Approx. 10.2 A
Micro and Bottom Grill .......... 1.95 kW Approx. 8.5 A
Dual cooking Micro and Convection 2.4 kW Approx. 10.2A
Power Output
Top Grill Grill heating element Power Output
Bottom heating element Power Output
Case Dimensions Width 520 mm Height 309 mm (including foot) Depth 488 mm
Cooking Cavity Dimensions Width 349 mm Height 207 mm Depth 357 mm
Turntable diameter 325 mm
Control Complement Touch Control System
Set Weight Approx. 20 kg
900 W nominal of RF microwave energy (measured by method of IEC 705)
Operating frequency 2450 MHz
1.0 kW
0.5 kW
Clock (1:00 - 12:59) / Timer (0 - 99 minutes 90 sec.)
Microwave Power for Variable Cooking
Repetition Rate;
100 (HIGH) ....................... Full power throughout the cooking time
70 (MEDIUM HIGH) ......................... approx. 70% of FULL Power
50 (MEDIUM) ................................... approx. 50% of FULL Power
30 (MEDIUM LOW).......................... approx. 30% of FULL Power
10 (LOW) ......................................... approx. 10% of FULL Power
Convection temperature control range:
250˚C, 230˚C, 220˚C, 200˚C, 180˚C, 160˚C, 130˚C, 100˚C, 70˚C and 40˚C
TIME keys, BREAKFAST key, PIZZA key,
AUTO COOK key, AUTO DEFROST key, INFO key, WEIGHT keys
LESS/MORE keys,
DUAL CONVECTION/GRILL key, MICROWAVE POWER LEVEL key
STOP/CLEAR key, START/AUTO MINUTE key,
WEIGHT CONVERSION key, AUTO START/CLOCK key,
CONVECTION TEMPERATURE key, GRILL key
INSTANT COOK keys
TIMER key
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-872M - 3
10sec.
10min.
1min.
Instant Cook
AUTO
COOK
AUTO
DEFROST
Kg Lb
LESS
GRILL
TIMER
Kg/Lb
DUAL
CONVECTION
GRILL
MORE
CONVE
CTION
C)
MICROWAVE
POWER LEVEL
STOP/
CLEAR
AUTOSTART
CLOCK
START
AUTO MINUTE
g oz
APPEARANCE VIEW
OVEN
3
8
9
1. Control panel
2. Oven lamp
3. Grill heating element (Top Grill)
4. Door opening button
5. Waveguide cover
6. Oven cavity
7. Turntable motor shaft
8. Grill heating element
(Bottom Grill)
7
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5
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12
13
9. Door seals and sealing surfaces
10.Ventilation openings
11.Outer cabinet
12.Power supply cord
13.Turntable
14.High rack
15.Low rack
CONTROL PANEL
11
10
14
15
COOK indicator showing oven in operation.
TOP GRILL indicator.
BOTTOM GRILL indicator
CONVECTION indicator.
MICROWAVE indicator.
WEIGHT indicators.
TIME keys.
Use to select cooking time.
BREAKFAST key.
AUTO COOK key.
WEIGH keys.
GRILL key.
Press to select Grill
CONVECTION TEMPERATURE key.
MICROWAVE POWER LEVEL key.
Press to select microwave
power level.
COOK
BREAKFAST
MIXED GRILL
FRESH FISH
RICE/PASTA FRESH VEG.
1 Chilled Ready Meals
1 Frozen Ready Meals
3 Roast Beef / 3
Roast Lamb 4 Minced Meat
4 Roast Pork 5 Bread
5 Roast Poultry
DEFROST
LBSKGOZ
%
PIZZA
CHICKEN PTNS
BAKED POTATOES
MINCED MEAT
OVEN CHIPS
1 Meat Joint
2 Poultry
Chicken Ptn, Steak, Chops
AUTO
nfo
CAKE
DEFROST indicator.
AUTO indicator, showing auto cooking on progress.
DIGITAL DISPLAY.
LESS/MORE indicators.
INFO indicator for interactive display.
% percentage microwave power level indicator.
PIZZA key. Press to cook pizza.
INSTANT COOK keys.
AUTO DEFROST key.
INFO key for interactive display.
LESS/MORE keys.
Press to shorten or lengthen heating time.
nfo
DUAL CONVECTION/GRILL key.
Press to select Dual Convection or Dual Grill.
STOP/CLEAR key.
Press once to stop a programme,
and/or twice to cancel a programme.
TIMER key
WEIGHT CONVERSION key
START/AUTO MINUTE key.
Press to start a programme. Press to cook on
R-872
(HIGH) for 1 minute or increase time during
cooking in multiples of 1 minute.
AUTO START/CLOCK key.
Use to set the clock.
R-872M - 4
OPERATION SEQUENCE
OFF CONDITION
Closing the door activates the monitored latch switch and
the stop switch.
IMPORTANT:
When the oven door is closed, the contacts COM-NC
of the monitor switch must be open. When the microwave oven is plugged in a wall outlet (230 - 240V /
50Hz), the line voltage is supplied to the noise filter.
Figure O-1 on page 30
1. The control unit is not energized. The display shows
nothing (Fig. O-1 (a)).
2. Open the door. The contacts (COM-NC) of the monitored latch switch are closed and the control unit is
energized. Then contacts of relays RY1 and RY5 are
closed, and the oven lamp will light and the display will
show "ENERGY SAVE MODE" (Fig. O-1(b)).
3. Close the door. The contacts (COM-NC) of the monitored latch switch are opened and the contacts of relay
RY1 are opened and the oven lamp will be turned off.
The display will show " . 0". (Fig. O-1(c)).
NOTE: Energy save mode
1. If the oven has not been used for more than 2 minutes,
the contacts of the relay RY5 will be opened and the
control unit will be not energized. Open and close the
door, the control unit will resume.
2. If the clock is set, this energy save mode does not work.
MICROWAVE COOKING CONDITION
HIGH COOKING
Enter a desired cooking time by touching the TIME keys
and start the oven by touching START key.
Function sequence Figure O-2 on page 31
CONNECTED COMPONENTS RELAY
Oven lamp, Turntable motor RY1
High voltage transformer RY2
Fan motor RY6
1. The line voltage is supplied to the primary winding of
the high voltage transformer. The voltage is converted
to about 3.3 volts A.C. output on the filament winding
and high voltage of approximately 2000 volts A.C. on
the secondary winding.
2. The filament winding voltage (3.3 volts) heats the
magnetron filament and the high voltage (2000 volts) is
sent to the voltage doubling circuit, where it is doubled
to negative voltage of approximately 4000 volts D.C..
3. The 2450 MHz microwave energy produced in the
magnetron generates a wavelength of 12.24 cm. This
energy is channelled 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 signal tone is heard and
the relays RY1 + RY2 + RY6 go back to their home
position. The circuits to the oven lamp, high voltage
transformer, fan motor and turntable motor are cut off.
5. When the oven door is opened during a cooking cycle,
the switches come to the following condition.
Switch Contact Condition
Monitored latch switch
Stop switch
Monitor Switch
COM-NO Closed Opened
COM-NC Opened Closed
COM-NO Closed Opened
COM-NO Closed Opened
COM-NC Opened Closed
During Oven Door
Cooking Open(No cooking)
R-872M - 5
The circuit to the high voltage transformer is cut off when
the contacts of relay RY2, and the contacts (COM-NO) of
the monitored latch switch and monitor switch are made
open. The circuit to the fan motor is cut off when the relay
RY6 is made open. The circuit to the turntable motor is cut
off when the contacts (COM-NO) of the monitored latch
switch are made open. The relay RY2 and RY6 are made
open when the door is opened. The oven lamp 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 remaining time.
6. MONITOR SWITCH CIRCUIT
The monitor switch is mechanically controlled by the
oven door, and monitors the operation of the monitored latch switch.
6-1. When the oven door is opened during or after the
cycle of a cooking program, the monitored latch
switch and stop switch must open their contacts
(COM-NO) first.
And
the contacts (COM-NC) of the
monitored latch switch are made closed. After that the
contacts (COM-NC) of the monitor switch can be
closed and the contacts (COM-NO) of monitor switch
are made open.
6-2. When the oven door is closed, the contacts (COM-
NC) of the monitor switch SW3 must be opened and
the contacts (COM-NO) of monitor switch must be
closed. After that the contacts (COM-NO) of the
monitored latch switch and the stop switch are made
closed.
latch switch are made open
And
the contacts (COM-NC) of the monitored
.
6-3. When the oven door is opened and the contacts
(COM-NO) of the monitored latch switch remain
closed, the fuse F8A will blow. Because the relay RY1
and monitor switch are closed and a short circuit is
caused.
MEDIUM HIGH, MEDIUM, MEDIUM LOW, LOW
COOKING
When the microwave oven is preset for variable cooking
power, the line voltage is supplied to the high voltage
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.
32 sec. ON
900W (HIGH)
MEDIUM
630W
450W (MEDIUM) Approx. 50%
MEDIUM
270W
90W (LOW) Approx. 10%
24 sec. ON 8 sec. OFF
HIGH
18 sec. ON
12 sec. ON
LOW
6 sec. ON
14 sec. OFF
20 sec. OFF
26 sec. OFF
100%
Approx. 70%
Approx. 30%
Note: The On/Off time ratio does not exactly correspond
to the percentage of microwave power, because
approx. 3 seconds are needed for heating up the
magnetron filament.
GRILL COOKING CONDITION
TOP GRILL (Figure O-3a)
In this condition the food is cooked by the top grill heating
element . Programme the desired cooking time by touching the TIME keys and touh the GRILL key once. When the
OPERATION SEQUENCE
STARTkey is touched, the following operations occur:
1. The numbers on the digital readout start the count
down to zero.
2. The oven lamp, cooling fan motor and turntable motor
are energized.
3. The relay RY3 is energized and the main supply
voltage is applied to the top grill heating element .
4. Now, the food is cooked by the top grill heating element.
BOTTOM GRILL (Figure O-3b)
In this condition the food is cooked by bottom grill heating
element energy. Programme the desired cooking time by
touching the TIME keys and touh the GRILL key twice.
When the STARTkey is touched, the following operations
occur:
1. The numbers on the digital readout start the count
down to zero.
2. The oven lamp, cooling fan motor and turntable motor
are energized.
3. The relay RY4 is energized and the main supply
voltage is applied to the bottom grill heating element .
4. Now, the food is cooked by the bottom grill heating
element .
TOP AND BOTTOM GRILL (Figure O-3c)
In this condition the food is cooked by top and bottom grill
heating elements energy. Programme the desired cooking time by touching the TIME keys and touh the GRILL
key three times. When the STARTkey is touched, the
following operations occur:
1. The numbers on the digital readout start the count
down to zero.
2. The oven lamp, cooling fan motor and turntable motor
are energized.
3. The relay RY4 is energized and the main supply
voltage is applied to the bottom grill heating element.
4. The relay RY3 is energized and the main supply
voltage is applied to the top grill heating element.
5. Now, the food is cooked by the top and bottom grill
heating elements.
CONVECTION COOKING CONDITION
PRE-HEATING (Figure O-4)
Programme the desired convection temperature by touching CONVECTION TEMPERATURE key. When the
STARTkey is touched, the following operations occur:
1. The coil shut-off relays RY1 and RY6 are energized,
the oven lamp, cooling fan motor and turntable motor
are turned on.
2. The coil shut-off relays RY3 and RY4 are energized by
control unit and the main supply voltage is added to the
top and bottom heating elements.
3. When the oven temperature reaches the selected preheat temperature, the following operations occur:
3-1. The coil shut-off relays RY3 and RY4 are energized
by control unit temperature circuit and thermistor,
opening the circuit to the top and bottom grill heating
elements.
3-2. The oven will continue to function for 30 minutes,
turning the top and bottom heating elements on and
off, as needed to maintain the selected pre-heat
R-872M - 6
temperature. The ovenwill shut-down completely after 30 minutes.
NOTE: The fan motor will be turned on and off at
preheating. And the convection motor will be turned
off at preheating. See "Power setting" on page 9.
CONVECTION COOKING (Figure O-4)
When the pre-heat temperature is reached, a beep signal
will sound indicating that the holding the temperature has
been reached in the oven cavity. Open the door and place
the food to cooked in the oven. Program desired cooking
time by touching the TIME keys and program convection
temperature by touching the CONVECTION TEMPERATURE key . When the START key is touched, the following
operations occur:
1. The numbers on the digital readout start the count
down to zero.
2. The oven lamp, cooling fan motor, turntable motor and
convection motor are energized.
NOTE: When the convection temperature 40˚C is se-
lected, the convection motor is not energized.
3. The relays RY3 and RY4 are energized (if the cavity
temperature is lower than selected temperature) and
the main supply voltage is applied to the top and
bottom heating elements to return to the selected
cooking temperature.
4.
Upon completion of the cooking time, the audible signal will sound, and the oven lamp, turntable motor,
cooling fan motor, convection motor, top and bottom
heating elements are de-energized. At the end of
convection cycle, if the cavity air temperature rise
above 120˚C, the circuit to the relay RY6 will be maintained (by the thermistor circuit) to continue operation
of the cooling fan motor until temperature drops below
105˚C, at that time the relay RY6 will be de-energized,
turning off the fan motor.
DUAL COOKING CONDITION
MICROWAVE AND CONVECTION (Figure O-5a)
Programme the desired cooking time by touching the
TIME keys. Touch the DUAL CONVECTION/GRILL key
once. Select the microwave power level by touching the
MICROWAVE POWER LEVEL key. And select the convection temperature by touching the CONVECTION TEMPERATURE key.
NOTE: The microwave power level can be selected from
90W, 270W and 450W.
When the STARTkey is touched, the following operations
occur:
1. The numbers on the digital readout start the count
down to zero.
2. The oven lamp, cooling fan motor, turntable motor and
convection motor are energized.
3. The relay RY3 will be energized and the main supply
voltage is applied to the top grill heatier.
4. The relay RY4 is energized (if the cavity temperature is
lower than selected temperature) and the main supply
voltage is applied to the bottom heating elementer.
5. The relay RY2 is energized and the microwave energy
is generated by magnetron.
6. Now, the food is cooked by microwave and convection
energy simultaneously.
OPERATION SEQUENCE
MICROWAVE AND TOP GRILL (Figure O-5b)
Programme the desired cooking time by touching the
TIME keys. Touch the DUAL CONVECTION/GRILLL key
twice. Select the microwave power level by touching the
MICROWAVE POWER LEVEL key. When the STARTkey
is touched, the following operations occur:
1. The numbers on the digital readout start the count
down to zero.
2. The oven lamp, cooling fan motor and turntable motor
are energized.
3. The relay RY3 is energized and the main supply
voltage is applied to the top grill heating element.
4. The relay RY2 is energized and the microwave energy
is generated by magnetron.
5. Now, the food is cooked by microwave and top grill
simultaneously.
MICROWAVE AND BOTTOM GRILL (Figure O-5c)
Programme the desired cooking time by touching the
TIME keys. Touch the DUAL CONVECTION/GRILL three
times. Select the microwave power level by touching the
MICROWAVE POWER LEVEL key. When the STARTkey
is touched, the following operations occur:
1. The numbers on the digital readout start the count
down to zero.
2. The oven lamp, cooling fan motor and turntable motor
are energized.
3. The relay RY4 is energized and the main supply
voltage is applied to the bottom grill heating element.
4. The relay RY2 is energized and the microwave energy
is generated by magnetron.
5. Now, the food is cooked by microwave and bottom grill
simultaneously.
POWER SETTING
Following table shows each power setting of the top
heating element, bottom heating element, magnetron, fan
motor and convection motor on Convection cooking mode,
Dual (Micro + Convec.) mode and Convection preheating
mode.
CONV. COOKING DUAL/CONVEC. COOKING
TOP BOTTOM TOP BOTTOM MAGNETRON FAN CTION
HEATER HEATER HEATER HEATER (MICRO) MOTOR MOTOR
250˚C 70% 70% 70% 70% 10, 30, 50% 100% 100%
230˚C 60% 70% 50% 70% 10, 30, 50% 100% 100%
220˚C 40% 70% 40% 70% 10, 30, 50% 100% 100%
200˚C 40% 60% 40% 60% 10, 30, 50% 100% 100%
180˚C 40% 50% 40% 50% 10, 30, 50% 100% 100%
160˚C 20% 40% 20% 40% 10, 30, 50% 100% 100%
130˚C 20% 30% 20% 30% 10, 30, 50% 100% 100%
100˚C 20% 20% 20% 20% 10, 30, 50% 100% 100%
70˚C 10% 20% 10% 20% 10, 30, 50% 100% 100%
40˚C 10% 10% 10% 10% 10, 30, 50% 100% 0%
CONVECTION PREHEATING
TOP HEATER BOTTOM HEATER FAN MOTOR CONV. MOTOR
250˚C 100% 100% 60% 0%
230˚C 100% 100% 60% 0%
220˚C 100% 100% 60% 0%
200˚C 100% 100% 60% 0%
180˚C 100% 100% 60% 0%
160˚C 100% 100% 60% 0%
130˚C 100% 100% 60% 0%
100˚C 100% 100% 60% 0%
70˚C 100% 100% 60% 0%
40˚C 100% 100% 60% 0%
ON/OFF TIME RATIO
In grill cooking, convection cooking or dual cooking, the
top heater, bottom heater or magnetron operate whithin a
48 second time base. The following table is the ON / OFF
CONVE
time ratio at each power output of the top heaters, bottom
heater or magnetron.
POWER OUTPUT ON TIME OFF TIME
100% 48 sec. 0 sec.
90% 44 sec. 4 sec.
80% 40 sec. 8 sec.
70% 36 sec. 12 sec.
60% 32 sec. 16 sec.
50% 26 sec. 22 sec.
40% 22 sec. 26 sec.
30% 16 sec. 32 sec.
20% 12 sec. 36 sec.
10% 8 sec. 40 sec.
AUTOMATIC COOKING
PIZZA
BREAKFAST
INSTANT COOK
AUTO COOK
AUTO DEFROST
Above functions are automatic cooking. They automatically work out the correct cooking mode and cooking time
and/or cooking temperature. They will cook according to
the special cooking sequence.
LIMITATIONS OF POWER OUTPUT IN MANUAL
OPERATION
After the same cooking mode is carried out for more than
the specified cooking time, the power output is automatically reduced by turning the control relays on and off
intermittently, as shown in the table below. This is to
protect the oven door against temperature rising.
Cooking mode time (minutes) output (%) (seconds)
Microwave (100%)
Top grill 30 50 48
Bottom grill 45 50 48
Top grill and 15 (Top) 50 48
Bottom grill 15(Bottom) 50 48
Micro. (100%) 20 (Micro.) 70 48
D
+ Top grill 15 (Grill) 50 48
U
A
Micro. (100%) 20 (Micro.) 70 48
L
+ Bottom grill 15 (Heater) 50 48
NOTE:
1. In case of Automatic operations, the limitations of
power output are not carried out.
2. In case that the stop key is touched or the oven door is
opened during cooking, the limitations of power output
are not carried out after the total cooking time beyond
the specified cooking time.
3. In case of the two or more same cooking modes are
carried out, the limitations of power output are not
carried out after the total cooking time beyond the
specified cooking time.
4. In case of the two or more different cooking modes are
carried out, the specified cooking time is started to
count from the point when the cooking mode is changed.
5. If the cooking mode has the power level display, the
power level is also displayed when the limitations of
power output are carried out.
Specified cooking Limited power Time base
20 70 32
R-872M - 7
FUNCTION OF IMPORTANT COMPONENTS
DOOR OPEN MECHANISM
The door can be opened by pushing the open button on the
control panel. When the open button is pushed, the open
lever pushes the lower latch head on the door upward.
The upper latch head is linked with the lower latch head,
so now, the door can be opened.
DOOR
LATCH
HEADS
LATCH HOOK
MONITOR SWITCH
MONITORED
LATCH SWITCH
STOP SWITCH
OPEN LEVER
Figure D-1. Door Open Mechanism
MONITORED LATCH SWITCH
1. When the oven door is closed, the contacts (COM-NO)
of the switch must be closed. And the contacts (COMNC) must be opened.
2. When the oven door is opened, the contacts (COMNO) of the switch must be opened. And the contacts
(COM-NC) must be closed.
STOP SWITCH
1. When the oven door is closed, the contacts (COM-NO)
of the switch must be closed.
2. When the oven door is opened, the contacts (COMNO) of switch must be opened.
MONITOR SWITCH
The monitor switch is activated (the contacts 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
blowing the fuse F8A when the contacts of the monitored
latch switch fail to open when the door is opened.
Function
1. When the door is opened, the contacts (COM-NC) of
monitor switch close (to the ON condition) due to their
being normally closed and contacts (COM-NO) open.
At this time the contacts (COM-NO) of monitored latch
switch is in the OFF condition (contacts open) due to
their being normally open contact switches.
2. As the door goes to a closed position, the monitor
switch contacts (COM-NC) are opened and contacts
(COM-NO) closed and then contacts (COM-NO) of
monitored latch switch and stop switch are closed.(On
opening the door, each of these switches operate
inversely.)
3. If the door is opened and the monitored latch switch
contacts (COM-NO) fail to open, the fuse F8A blows
immediately after closing of the monitor switch (COMNC) contacts.
CAUTION: BEFORE REPLACING A BLOWN FUSE F8A,
TEST THE MONITORED LATCH SWITCH
AND MONITOR SWITCH FOR PROPER
OPERATION. (REFER TO CHAPTER “TEST
PROCEDURE”).
FUSE 15A 250V
If the wire harness or electrical components are shortcircuited, this fuse blows to prevent an electric shock or fire
R-872M - 8
hazard.
FUSE F8A 250V
1. If the wire harness or electrical components are shortcircuited, this fuse blows to prevent an electric shock or
fire hazard.
2. The fuse also blows when the monitored latch switch
remains closed with the oven door open and when the
monitor switch contact (COM-NC) closes.
3. The fuse also blows when the asymmetric rectifier,
H.V. rectifier,.H.V. wire harness, H.V. capacitor,
magnetron or secondary winding of high voltage transformer is shorted.
TC TRANSFORMER
T/C transformer converts A.C. line voltage into low voltage
to drive the control unit.
THERMAL CUT-OUT 125˚C (MG)
This thermal cut-out protects the magnetron against overheat. If the temperature goes up higher than 125˚C because the fan motor is interrupted or the ventilation openings are blocked, the thermal cut-out will open and line
voltage to the high voltage transformer will cut off and
operation of the magnetron will be stopped. The defective thermal cut-out must be replaced with a new one.
THERMAL CUT-OUT 150˚C (OVEN)
This thermal cut-out protects the oven against the overheat during grill cooking, convection cooking or dual
(combination) cooking. If the temperature rises above
150˚C because the fan motor is interrupted, the air inlet
duct is blocked or the ventilation openings are obstructed,
the thermal cut-out opens and switches off all the electrical
parts. When the cools itself down to the operating temperature of 130˚C, the contacts of the thermal cut-out will
close again.
ASYMMETRIC RECTIFIER
The asymmetric rectifier is solid state device that prevents
current flow is both directions. And it prevents the temperature rise of the high voltage transformer by blowing
the fuseF8A when the high voltage rectifier is shorted.
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 the
blowing the fuseF8A.)
1. The high voltage rectifier is shorted by some fault when
D2 D1
ASYMMETRIC
RECTIFIER
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.
3. D2 of the rectifier is shorted.
4. The large electric currents flow through the high voltage winding of the high voltage transformer.
5. The large electric currents beyond 8A flow through the
primary winding of the high voltage transformer.
6. The fuse F8A blows by the large electric currents.
7. The power supplying to the high voltage transformer is
cut off.
HIGH VOLTAGE
RECTIFIER
FUNCTION OF IMPORTANT COMPONENTS
NOISE FILTER
The noise filter assembly prevents radio frequency interference that might flow back in the power circuit.
TURNTABLE MOTOR
The turntable motor rotates 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 channelled through the oven cavity to remove steam and
vapours given off from heating food. It is then exhausted
through the exhausting air vents of the oven cavity.
CONVECTION MOTOR
The convection motor drives the convection fan and
provide the heated air.
TOP GRILL HEATING ELEMENT
The grill heating element is provided to brown the food and
is located on the top of the oven cavity.
BOTTOM GRILL HEATING ELEMENT
The grill heating element is provided to brown the food and
is located at the base of the oven cavity.
CONVECTION COOKING SYSTEM
This oven is designed with a hot air heating system where
food is heated by forced circulation of the hot air produced
by the grill heaters. The air heated by the grill heating
elements is circulated through the convection passage
provided on the outer casing of the oven cavity by means
of the convection fan which is driven by the convection
motor. It is then enters the inside of the oven through the
vent holes provided on the back side of the oven. Next, the
hot air heats the food on the turntable and leaves the oven
cavity through the vent in the oven cavity rear wall. In this
way, the hot air circulates inside the oven cavity to raise its
temperature and, at the same time, comes into contact
with the food being cooked. When the temperature inside
the oven cavity reaches the selected temperature, the
heating elements are de-energized. When the temperature inside the oven cavity drops below the selected
temperature, the heating elements are energized again. In
this way, the inside of the oven cavity is maintained at
approximately the selected temperature. When the convection time reaches “0”, the heating elements are deenergized and the convection fan stops operating and the
oven shuts off. At that time if the cavity air temperature has
rised above120˚C, the fan motor remains rotating. Automatically the fan motor will be shut down at low temperature (less than 105˚C).
Door
Oven Cavity
Turntable
Motor
Insulation
Grill Heating
Element
Bottom Grill
Heating Element
Convection
Passage
Turntable
Cooling
Fan
Convection
Motor
Convection
Fan
Figure D-2. Convection Cooking System
FIRE SENSING FEATURE
The oven will stop its operation when there is a fire in the
oven cavity in microwave cooking condition.
LSI measures the voltage across the temperature measurement circuit intermittently within 32-seconds time base
since the oven is started in microwave cooking condition.
The oven will stop its operation when the difference of the
voltage is more than 0.781 volts in microwave cooking
condition.
1. Within a 32-seconds base, the thermistor is energized
for 2 seconds. At that time, the voltage across the
temperature measurement circuit is measured.
2. The oven carries out the procedure above again. If the
second voltage is 0.781V higher than first voltage, LSI
judges it is a fire in the oven cavity and stop the oven.
3. When LSI judges it is a fire in the oven cavity, LSI will
switch off the relays to high voltage transformer and fan
motor and LSI stops countring down.
THERMISTOR
Sensing
Voltage
ON
OFF
ON
OFF
Sensing the voltage across temperature measurement circuit.
30 32 (sec.)
OPEN JUDGE BY THERMISTOR
1. If the temperature of the thermistor does not rise to
more than 40˚C after 4 minutes and 15 seconds from
when the oven is started in convection, grill (top and
bottom grills) or dual cooking mode, the oven is turned
off.
2. When the thermistor or the wire harness to the thermistor is opened, the oven is turned off after 4 minutes and
15 seconds because this condition is same as above.
TROUBLESHOOTING GUIDE
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 Procedure” section.
IMPORTANT: If the oven becomes inoperative because of a blown fuse F8A in the monitored latch switch - monitor
switch circuit, check the monitored latch switch and monitor switch before replacing the fuse F8A.
R-872M - 9
TEST PROCEDURE
ABC DEEEFGGHHH I J K L L MNOOOOOOO P
H.V. RECTIFIER ASSEMBLY
HIGH VOLTAGE TRANSFORMER
MAGNETRON
MONITORED LATCH SWITCH SW1
HIGH VOLTAGE CAPACITOR
H.V. HARNESS
THERMISTOR
MONITOR SWITCH SW3
STOP SWITCH SW2
TURNTABLE MOTOR
THERMAL CUT-OUT 150˚C TC2
THERMAL CUT-OUT 125˚C TC1
NOISE FILTER
CONVECTION FAN MOTOR
FAN MOTOR
TOP GRILL HEATING ELEMENT
FUSE F8A
FUSE 15A
TOUCH CONTROL PANEL
TC TRANSFORMER
BOTTOM GRILL HEATING ELEMENT
RELAY RY2
RELAY RY1
KEY UNIT
RELAY RY5
RELAY RY4
RELAY RY3
FOIL PATTERN ON P.W.B.
RELAY RY7
RELAY RY6
NO POWER AT WALL OUTLET
HOME FUSE OR BREAKER
MIS-ADJUSTMENT OF SWITCHES
BLOCKED VENTILATION OPENINGS
OPENED WIRE HARNESS
SHORTED WIRE HARNESS
OVEN LAMP OR SOCKET
POWER SUPPLY CORD
TROUBLESHOOTING GUIDE
BLOCKED CINVECTION FAN
BLOCKED
CONDITION
OFF
CONDITION
R-872M - 10
COOKING
CONDITION
(COMMON MODE)
MICROWAVE
COOKING
CONDITION
CONVECTION
COOKING
CONDITION
GRILL COOKING
CONDITION
DUAL COOKING
CONDITION
(COMMON MODE)
DUAL COOKING
CONDITION
(MICRO./CONV.)
DUAL COOKING
CONDITION
(MICRO./GRILL)
POSSIBLE CAUSE
AND
DEFECTIVE PARTS
PROBLEM
Fuse F8A blows when the door is opened.
Home fuse blows when power cord is plugged into wall outlet.
Fuse 15A blows when power cord is plugged into wall outlet.
Nothing appears in display when power cord is plugged into wall outlet
and the door is opened and closed.
Display does not operate properly when STOP/CLEAR key is touched.
Oven lamp does not light when door is opened. (Display operates.)
Oven does not start when the START key is touched. (Display operates.)
Oven lamp does not light and turntable motor does not operate.
Fan motor does not operate. (Oven lamp lights.)
Convection fan motor does not operate. (Oven lamp lights.)
Turntable motor does not operate. (Oven lamp lights.)
Oven or any electrical parts (except fan motor) does not stop when
cooking time is 0 or STOP/CLEAR key is touched.
Oven stops after 4 minutes and 15 seconds since START key is
touched. (Except Microwave mode)
Display operates properly but all electrical parts do not operate.
Oven goes into cook cycle but shuts down before end of cooking cycle.
After cooking, the temperature of oven cavity is higher than 105˚C but
fan motor does not operate.
Oven seems to be operating but little or no heat is produced in oven
load. (Microwave power control is set at HIGH)
Oven does not seem to be operating properly during variable cooking
condition except HIGH cooking condition.
Oven goes into cook cycle but shuts down before end of cooking cycle.
Convection cooking mode does not heat.
Oven seems to be operating but the temperature in the oven cavity is
lower or higher than preset one.
Grill heating element does operate.
Oven goes into cook cycle but shuts down before end of cooking cycle.
Oven seems to be operating but little or no heat is produced in oven
load. (Microwave power does not seem to be generated properly)
Oven seems to be operating but the temperature in the oven cavity is
lower or higher than preset one.
Top and Bottom Grill heating elements do not heat.
Top or Bottom Grill heating element does not heat.
COOLING FAN
TEST PROCEDURES
PROCEDURE
LETTER
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 high voltage circuit by removing all leads connected to 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 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
The power output of this oven is rated using the method specified by IEC 705. Full details of how to
curry out this procedure can be found in the Sharp Technical Training notes which is available from
Sharp Parts Centre (part number SERV-LITMW01).
The IEC-705 procedure must be carried out using laboratory-type procedures and equipment.
These requirements make the procedure unsuitable for routine performance checks.
NOTE: The following test method gives an indication of the output power only, it cannot be used to
establish the actual/rated output power. If the true output power is required, then the IEC705
test method must be used.
COMPONENT TEST
Alternative simplified method:
1. Place 2 litres of cold water (between 12°C and 20°C) in a suitable container.
2. Stir the water and measure the temperature in °C. Note temperature as T1.
3. Place the container in the microwave and heat the water for 2 minutes on fill power.
4. When the 2 minutes is completed, remove the container and stir the water. Note temperature as
T2.
5. Calculate the output power using the following formula:
R.F. Power Output = (T2 - T1) x 70.
NOTE: The result from this test should be within the allowance of 2000cc alternative method.
(±10%).
MICROWAVE LEAKAGE TEST
This oven should be tested for microwave leakage on completion of any repair or adjustment, following
the procedure described in the Sharp Technical Training notes (part number SERV-LITMW01). The
maximum leakage permitted in BS EN 60335-2-25 is 50W/m2 (equivalent to 5W/m2), however it is not
normal to detect any significant leakage, therefore, any leakage which is detected should be
investigated.
It is essential that only leakage detectors with current calibration traceable to National Physical
Laboratories are used.
Suitable leakage detectors: CELTEC A100
APOLLO X1
B HIGH VOLTAGE TRANSFORMER TEST
WARNING: High voltage and large currents are present at the secondary winding and
filament winding of the high voltage transformer. It is very dangerous to work
near this part when the oven is on. NEVER make any voltage measurements
of the high-voltage circuits, including the magnetron filament.
R-872M - 11
TEST PROCEDURES
PROCEDURE
LETTER
CARRY OUT 3D CHECKS.
Disconnect the leads to the primary winding of the high voltage 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 winding. The following readings should be
obtained:-
a. Primary winding ................................... approximately 2 Ω
b. Secondary winding ............................ approximately 99 Ω
c. Filament winding......................................... less than 1 Ω
If the readings obtained are not stated as above, then the high voltage transformer is probably faulty
and should be replaced.
CARRY OUT 4R CHECKS.
C HIGH VOLTAGE RECTIFIER TEST
CARRY OUT 3D CHECKS.
Isolate the high voltage rectifier assembly from the HV circuit. The high voltage rectifier can be tested
using an ohmmeter set to its highest range. Connect the ohmmeter across the terminal B+C of the high
voltage rectifier and note the reading obtained. Reverse the meter leads and note this second reading.
The normal resistance is infinite in one direction and more than 100 kΩ in the other direction.
CARRY OUT 4R CHECKS.
COMPONENT TEST
AB
D2 D1
ASYMMETRIC RECTIFIER TEST
CARRY OUT 3D CHECKS.
Isolate the high voltage rectifier assembly from the HV circuit. The asymmetric rectifier can be tested
using an ohmmeter set to its highest range 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 the asymmetric rectifier is shorted
in either direction, then the asymmetric rectifier is probably faulty and must be replaced with high voltage
rectifier. When the asymmetric rectifier is defective, check whether magnetron, high voltage rectifier,
high voltage wire or filament winding of the high voltage 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.
D HIGH VOLTAGE CAPACITOR TEST
CARRY OUT 3D CHECKS.
A. Isolate the high voltage capacitor from the circuit.
B. Continuity check must be carried out with measuring instrument which is set to the highest
resistance range.
C. A normal capacitor shows continuity for a short time (kick) and then a resistance of about 10MΩ
after it has been charged.
D. A short-circuited capacitor shows continuity all the time.
E. An open capacitor constantly shows a resistance about 10 MΩ because of its internal 10MΩ
resistance.
F. When the internal wire is opened in the high voltage 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.
ASYMMETRIC
RECTIFIER
C
HIGH VOLTAGE RECTIFIER
CARRY OUT 4R CHECKS.
R-872M - 12
TEST PROCEDURES
PROCEDURE
LETTER
E SWITCH TEST
CARRY OUT
Isolate the switch to be tested and using an ohmmeter check between the terminals as described in
the following table.
Plunger Operation COM to NO COM to NC
Released Open circuit Short circuit
Depressed Short circuit Open circuit
If incorrect readings are obtained, make the necessary switch adjustment or replace the switch.
CARRY OUT 4R CHECKS.
F THERMISTOR TEST
CARRY OUT 3D CHECKS.
Disconnect theconnector B from CPU unit. Measure the resistance of the thermistor with an ohmmeter.
Connect the ohmmeter leads to Pin No's C1 and C3 of the thermistor harness.
If the meter does not indiicate above resistance, replace the thermistor.
CARRY OUT 4R CHECKS.
COMPONENT TEST
3D CHECKS.
Table: Terminal Connection of Switch
COM; Common terminal,
NO; Normally open terminal
NC; Normally close terminal
Room Temperature Resistance
20˚C - 30˚C Approximately 359.9 kΩ - 152 kΩ
G 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.
Temperature of "ON" Temperature of "OFF" Indication of ohmmeter
Parts Name condition (closed circuit). condition (open circuit). (When room temperature
(˚C) (˚C) is approx. 20˚C.)
Thermal cut-out 125˚C
Thermal cut-out 150˚C
If incorrect readings are obtained, replace the thermal cut-out.
An open circuit thermal cut-out (MG) indicates that the magnetron has overheated, this may be due to
resistricted ventilation, cooling fan failure.
An open circuit thermal cut-out (OVEN) indicates that the oven cavity has overheated, this may be due
to no load operation.
CARRY OUT 4R CHECKS.
H MOTOR WINDING TEST
CARRY OUT 3D CHECKS.
Table: Thermal Cut-out Test
This is not resetable Above 125˚C Closed circuit
Below 130˚C. Above 150˚C Closed circuit
Disconnect the leads from the motor. Using an ohmmeter, check the resistance between the two
terminals as described in the table below.
Table: Resistance of Motor
Motors Resistance
Fan motor Approximately 293 Ω
Turntable motor Approximately 15 kΩ
Convection fan motor Approximately 288 Ω
If incorrect readings are obtained, replace the motor.
CARRY OUT 4R CHECKS.
R-872M - 13
TEST PROCEDURES
PROCEDURE
LETTER
I NOISE FILTER TEST
CARRY OUT
Disconnect the leads from the terminals of noise filter.
Using an ohmmeter, check between the terminals as
described in the following table.
Between N and L Approx. 680 kΩ
Between terminal N and WHITE Short circuit
Between terminal L and RED Short circuit
If incorrect readings are absorbed, replace the noise filter unit.
COMPONENT TEST
3D CHECKS.
L
15A
L
Cx
L
N
Cy
F8A
L (min) Cx ± 20% Cy ± 20% R1 R2
1.0mH 0.22µF 4700pF 10 MΩ 680kΩ
MEASURING POINTS INDICATION OF OHMMETER
R2
WHT
R1
RED
CARRY OUT
J BLOWN FUSE 15A
CARRY OUT 3D CHECKS.
If the fuse15A is blown, there is a shorts or grounds in electrical parts or wire harness. Check them and
replace the defective parts or repair the wire harness.
CARRY OUT 4R CHECKS.
CAUTION: Only replace fuse
K BLOWN FUSE F8A
CARRY OUT 3D CHECKS.
1. If the fuse F8A is blown when the door is opened, check the monitored latch switch and monitor
switch.
2. If the fuse F8A is blown by incorrect door switching replace the defective switch(es) and the fuse
F8A.
3. If the fuse F8A is blown, there could be shorts in the asymmetric rectifier or there is a ground in wire
harness. A short in the asymmetric rectifier may be occurred due to short or ground in H.V. rectifier,
magnetron, high voltage transformer or H.V. wire. Check them and replace the defective parts or
repair the wire harness.
CARRY OUT 4R CHECKS.
CAUTION: Only replace fuse
L GRILL HEATING ELEMENT (TOP) AND BOTTOM HEATING ELEMENTS TEST
CARRY OUT 3D CHECKS.
4R CHECKS.
with the correct value replacement.
F8A with the correct value replacement.
Before carrying out the following tests make sure the heating element is cool completely.
1. Resistance of heating element.
Disconnect the wire leads to the heating element to be tested. Using ohmmeter with low resistance
range. Check the resistance across the terminals of the heating element as described in the
following table.
Table: Resistance of heating element
Parts name Resistance
Grill heating element (top) Approximately 61 Ω
Bottom heating element Approximately 115 Ω
2. Insulation resistance.
Disconnect the wire leads to the heating element to be tested. Check the insulation resistance
between the element terminal and cavity using a 500V - 100MΩ insulation tester. The insulation
resistance should be more than 10 MΩ in the cold start.
If the results of above test 1 and/or 2 are out of above specifications, the heating element is probably
faulty and should be replaced.
CARRY OUT 4R CHECKS.
R-872M - 14
TEST PROCEDURES
PROCEDURE
LETTER
COMPONENT TEST
M 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
can not 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 also the Control unit is divided into two units, CPU
unit and Power 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 N) 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 light up.
b) At a certain digit, brightness is low.
c) Only one indicator does not light up.
d) The corresponding segments of all digits do not light up; or they continue to light up.
e) Wrong figure appears.
f) A certain group of indicators do not light up.
g) The figure of all digits flicker.
2-3 Other possible troubles caused by defective control unit.
a) Buzzer does not sound or continues to sound.
b) Clock does not operate properly.
c) Cooking is not possible.
d) Proper temperature measurement is not obtained.
N KEY UNIT TEST
If the display fails to clear when the STOP/CLEAR pad is depressed, first verify the flat ribbon cable
is making good contact, verify that the door sensing switch (stop switch) operates properly; that is the
contacts are closed when the door is closed and open when the door is open. If the door sensing switch
(stop switch) is good, disconnect 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 jumper wire
between the pins that correspond to the STOP/CLEAR pad making 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 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.
G 8 G 7 G 6 G 5 G 4 G 3 G 2 G 1
MINCED MEAT
OVEN CHIPS
PIZZA
G12 G11 G10 G 9
CHICKEN PTNS
CAKE
MORE LESS
BAKED POTATOES
AUTO
DEFROST
FRESH FISH
FRESH VEG.
START
AUTO MINUTE
Kg / Lb
MIXED GRILL
RICE/PASTA
AUTO START
CLOCK
STOP/
CLEAR
10 sec. 1 min. 10 min.
AUTO
COOK
g • oz
MICROWAVE
POWER LEVEL
GRILL
CONVECTION
( ˚C )
DUAL
CONVECTION/
GRILL
BREAKFAST
Kg • Lb
TIMER
R-872M - 15
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