Sharp R-951M Service Manual ▷ View online
R-951M - 5
Figure D-1. Door Open Mechanism
NOTE: If the damper door is not in the proper position,
closed durining convection, grill or dual, or open
durning microwave, the control unit will stop oven
operation after 1 minute.
durning microwave, the control unit will stop oven
operation after 1 minute.
4. Operation of damper is shown below;
Damper operation
Cooking condition
Operation of Damper
Microwave
Convection
Grill;
during backed up with con
vection heater
vection heater
Grill;
after convection heater
back- up has stopped.
back- up has stopped.
Dual
(Microwave and Convec
tion) when oven tempera
ture above 220˚C is pro
grammed.
tion) when oven tempera
ture above 220˚C is pro
grammed.
When oven temperature be-
low 200˚C is programmed.
Dual (Microwave and Grill)
Fire sensing condition
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 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.
the control panel. When the open button is pushed, the
open lever pushes 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.
Latch head
Door
Monitor switch
Monitored latch switch
Door switch
Open lever
DAMPER OPEN-CLOSE MECHANISM
Damper position is set automatically by damper motor,
damper switch, damper cam and damper shaft.
These components are operated by a signal that judges if
microwave cooking or other cooking operation is selected
by the CPU unit.
damper switch, damper cam and damper shaft.
These components are operated by a signal that judges if
microwave cooking or other cooking operation is selected
by the CPU unit.
Microwave Cooking:
Damper is in the open position, because a portion of
cooling air is channeled through the cavity to remove
steam and vapors given off from the heating foods.
It is then exhausted at the top of the oven cavity into a
condensation compartment.
cooling air is channeled through the cavity to remove
steam and vapors given off from the heating foods.
It is then exhausted at the top of the oven cavity into a
condensation compartment.
Convection Cooking:
Damper is in the closed position, so that no hot air will be
allowed to leak out the oven cavity.
allowed to leak out the oven cavity.
Damper Operation
1. When power supply cord is plugged in:
1-1. When power supply cord is plugged in, a signal is
1-1. When power supply cord is plugged in, a signal is
sensed in the control unit, and operates shut-off relay
(RY6).
(RY6).
1-2. Contacts of shut-off relay (RY6) close, the damper
motor is energized, opening the damper door.
1-3. When the damper is moved to the open position by
the damper cam, damper switch is closed (ON posi-
tion).
tion).
1-4. The signal of damper switch is re-sensed in the
control unit and shut-off relay (RY6) is turned off.
1-5. The A.C. line voltage A.C. to the damper motor is
stopped and the motor turns off.
2. When oven is microwave cooking:
Damper is in the open position
3. When oven is convection cooking:
3-1 Damper motor is energized right after the oven is
3-1 Damper motor is energized right after the oven is
started.
3-2. When damper is in the closed position (damper
switch is OFF), its signal is sensed by the control unit,
and shut-off relay (RY7) is de-energized.
and shut-off relay (RY7) is de-energized.
3-3. The damper is held in the closed position during the
cooking operation
3-4. At the end of any cooking, when the fan motor stops,
the relay (RY6) is energized and the damper is
returned to the open position.
returned to the open position.
FIRE SENSING FEATURE
This model incorporates a sensing feature which will stop
the oven's operation if there is a fire in the oven cavity
during microwave cooking.
This accomplished by the LSI repeatedly measures the
voltage across the temperature measurement circuit (ther-
mistor) during it's 32-seconds time base comparing the
obtained voltage measurements. If the most recent volt-
age measured is 300mV grater than the previous voltage
measured, the LSI judges it as a fire in the oven cavity and
switches off the relays to the high voltage transformer, fan
motor and convection motor. The LSI also stops counting
down and closes the damper door so that no fresh air will
enter the oven cavity. Please refer to the following section
for a more detailed description.
the oven's operation if there is a fire in the oven cavity
during microwave cooking.
This accomplished by the LSI repeatedly measures the
voltage across the temperature measurement circuit (ther-
mistor) during it's 32-seconds time base comparing the
obtained voltage measurements. If the most recent volt-
age measured is 300mV grater than the previous voltage
measured, the LSI judges it as a fire in the oven cavity and
switches off the relays to the high voltage transformer, fan
motor and convection motor. The LSI also stops counting
down and closes the damper door so that no fresh air will
enter the oven cavity. Please refer to the following section
for a more detailed description.
Operation
Please refer to the timing diagram on page 4.
1. The thermistor operates within a 32-seconds time base
and it is energized for three (3) seconds and off for 29
seconds. Two (2) seconds after the thermistor is
energized, the voltage across the temperature meas-
urement circuit is sampled by the LSI and twenty one
(21) seconds after the thermistor is cut off the LSI turns
on the cooling fan for six (6) seconds.
seconds. Two (2) seconds after the thermistor is
energized, the voltage across the temperature meas-
urement circuit is sampled by the LSI and twenty one
(21) seconds after the thermistor is cut off the LSI turns
on the cooling fan for six (6) seconds.
2. The above procedure is repeated. If the difference
between the first voltage measured (in step 1) and the
voltage measured when the procedure is repeated
(step 2) is greater than 300mV the LSI makes the
judgment that there is a fire in the oven cavity and will
switch off the relays to the high voltage transformer, fan
motor and convection motor. The LSI also stops count-
ing down and closes the damper door so that no fresh
air will enter the oven cavity.
voltage measured when the procedure is repeated
(step 2) is greater than 300mV the LSI makes the
judgment that there is a fire in the oven cavity and will
switch off the relays to the high voltage transformer, fan
motor and convection motor. The LSI also stops count-
ing down and closes the damper door so that no fresh
air will enter the oven cavity.
Open
Close
Close
Open
Close but open
after 20 minutes.
after 20 minutes.
Close
Open
Close
R-951M - 6
3. Once the fire sensor feature has shut the unit down,
the programmed cooking cycle may be resumed by
pressing the "START" pad or the unit may be reset by
pressing the "CLEAR" pad.
pressing the "START" pad or the unit may be reset by
pressing the "CLEAR" pad.
CONVECTION
MOTOR
THERMISTOR
Sensing
Voltage
ON
OFF
ON
OFF
ON
OFF
0
21
27 29
64 (sec.)
Sensing the voltage across temperature measurement circuit.
6 sec.
3 sec.
MICROWAVE OUTPUT POWER (IEC-705)
The power output of this oven is rated using the method specified by IEC-705. Full details of how to carry out this
procedure can be found in the Sharp Technical Training notes which is available from Sharp Parts Centre
(part number SERV-LITMW01).
procedure can be found in the Sharp Technical Training notes which is available from Sharp Parts Centre
(part number SERV-LITMW01).
Using this procedure, the heating time to raise 1000g of water by 10
°
C is approximately 50 seconds.
The IEC-705 procedure must be carried out using laboratory-type procedures and equipment. These requirements
make the procedure unsuitable for routine performance checks. An indication of the power being produced by the
oven
can however be obtained using the procedure given below.
Alternative simplified method:
1. Place 2 litres of cold water (between 12
make the procedure unsuitable for routine performance checks. An indication of the power being produced by the
oven
can however be obtained using the procedure given below.
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 full power.
4. When the 2 minutes is completed, remove the container and stir the water. Note the water temperature as T2.
5. Calculate the output power using the following formula:
4. When the 2 minutes is completed, remove the container and stir the water. Note the water 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 10% of the power rating stated on the rating label.
MICROWAVE LEAKAGE TEST
This oven should be tested for microwave leakage on completion of any repair or adjustment, following the proce-
dure described in the Sharp Technical Training notes (part number SERV-LITMW01). The maximum leakage
permitted in BS EN 60335-2-25 is 50W/m
dure described in the Sharp Technical Training notes (part number SERV-LITMW01). The maximum leakage
permitted in BS EN 60335-2-25 is 50W/m
2
(equivalent to 5mW/cm
2
), however it is not normal to detect any signifi-
cant leakage, therefore, any leakage which is detected should be investigated.
It is essential that only leakage detectors with current calibration traceable to the National Physical Laboratories are
used.
used.
Suitable leakage detectors :
CELTEC A100
APOLLO X1
APOLLO X1
FUNCTION OF IMPORTANT COMPONENTS
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 or
dual cooking (Microwave and Convection) mode,
the oven is turned off.
from when the oven is started in convection, grill or
dual cooking (Microwave and Convection) 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.
minutes and 15 seconds because this condition is
same as above.
OUTPUT POWER TEST PROCEDURE
R-951M - 7
TOUCH CONTROL
KEY UNIT TEST
If the display fails to clear when the STOP/CLEAR pad is depressed, first verify the flat ribbon cable is marking
good contact, verify that the door sensing switch (stop switch) operates properly; that is the contacts are closed
when the door is closed and open when the door is open. If the door sensing switch (stop switch) is good,
disconnecct the flat ribbon cable that connects the key unit to the control unit and make sure the door sensing
switch is closed (either close the door or short the door sensing switch connecter). Use the Key unit matrix
indicated on the control panel schematic and place a jumper wire between the pins that correspond to the
STOP/CLEAR pad marking momentary contact. If the control unit responds by clearing with a beep the key unit
is faulty and must be replaced. If the control unit does not respond, it is a faulty and must be replaced. If a
specific pad does not respond, the above method may be used (after clearing the control unit) to determine if
the control unit or key pad is at fault.
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,
disconnecct the flat ribbon cable that connects the key unit to the control unit and make sure the door sensing
switch is closed (either close the door or short the door sensing switch connecter). Use the Key unit matrix
indicated on the control panel schematic and place a jumper wire between the pins that correspond to the
STOP/CLEAR pad marking momentary contact. If the control unit responds by clearing with a beep the key unit
is faulty and must be replaced. If the control unit does not respond, it is a faulty and must be replaced. If a
specific pad does not respond, the above method may be used (after clearing the control unit) to determine if
the control unit or key pad is at fault.
CARRY OUT 4R CHECKS.
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
troubleshooting by unit replacement is described according to the symptoms indicated.
1.
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
troubleshooting by unit 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.
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.
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.
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.
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.
b) Clock does not operate properly.
c) Cooking is not possible.
d) Proper temperature measurement is not obtained.
G11
G7
G2
G5. 9
G12
AUTO
START
CLOCK
AUTO
COOK
AUTO
DEFROST
STOP/
CLEAR
Kg / Lb
Kg • Lb
CHICKEN PORTIONS
BOILED POTATOES
BAKED POTATOES
FRESH FISH
YORKSHIRE PUDDING
RICE / PASTA
OVEN CHIPS
FRESH VEG.
FROZEN VEG.
g • oz
MORE
GRILL
TIMER
LESS
10min.
10sec.
1min.
DUAL
CONVECTION/
GRILL
CONVECTION
TEMPERATURE
MICROWAVE
POWER LEVEL
START
AUTO MINUTE
G10
G8
G6
G4
G1
G3
R-951M - 8
TOUCH CONTROL
CONT
...
PROCEDURES TO BE TAKEN WHEN THE FOIL PATTERN ON THE PRINTED WIRING BOARD (PWB) IS OPEN.
To protect the electronic circuits, this model is provided with a fine foil pattern added to the input circuit on the PWB,
this foil pattern acts as a fuse. If the foil pattern is open, follow the troubleshooting guide given below for repair.
Problem: POWER ON, indicator does not light up.
this foil pattern acts as a fuse. If the foil pattern is open, follow the troubleshooting guide given below for repair.
Problem: POWER ON, indicator does not light up.
CARRY OUT 3D CHECKS.
STEPS
OCCURANCE
CAUSE OR CORRECTION
1
The rated AC voltage is not present at
Check supply voltage and oven power cord.
Power terminal of CPU connector (CN-A).
2
The rated AC voltage is present at primary
Low voltage transformer or secondary circuit defective.
side of low voltage transformer.
Check and repair.
3
Only pattern at "a" is broken.
*Insert jumper wire J1 and solder.
(CARRY OUT 3D CHECKS BEFORE REPAIR)
4
Pattern at "a" and "b" are broken.
*Insert the coil RCILF2003YAZZ between "c" and "d".
(CARRY OUT 3D CHECKS BEFORE REPAIR)
NOTE: *At the time of these repairs, make a
visual inspection of the varistor for burning
damage and examine the transformer with
tester for the presence of layer short circuit
(check primary coil resistance).
If any abnormal condition is detected, replace
the defective parts.
visual inspection of the varistor for burning
damage and examine the transformer with
tester for the presence of layer short circuit
(check primary coil resistance).
If any abnormal condition is detected, replace
the defective parts.
CARRY OUT 4R CHECKS.
RELAY TEST
CARRY OUT 3D CHECKS.
Remove the outer case and check voltage between Pin Nos. 1 and 3 of the 4 pin connector (E) on the control
unit with an A.C. voltmeter.
The meter should indicate 230-240 volts, if not check oven circuit.
unit with an A.C. voltmeter.
The meter should indicate 230-240 volts, if not check oven circuit.
Relay Test
Check voltage at the relay coil with a D.C. voltmeter during the microwave cooking operation, convection cooking
operation or grill operation.
Check voltage at the relay coil with a D.C. voltmeter during the microwave cooking operation, convection cooking
operation or grill operation.
DC. voltage indicated ........... Defective relay.
DC. voltage not indicated ..... Check diode which is connected to the relay coil. If diode is good, control unit
is defective.
DC. voltage not indicated ..... Check diode which is connected to the relay coil. If diode is good, control unit
is defective.
RELAY SYMBOL
OPERATIONAL VOLTAGE
CONNECTED COMPONENTS
RY1
Approx. 18.0V D.C.
Oven lamp / Turntable motor
RY2
Approx. 18.0V D.C.
High voltage transformer
RY3
Approx. 18.0V D.C.
Convection heating element
RY4
Approx. 18.0V D.C.
Grill heating element
RY5
Approx. 24.0V D.C.
Fan motor
RY6
Approx. 24.0V D.C.
Convection fan motor
RY7
Approx. 24.0V D.C.
Damper motor
CARRY OUT 4R CHECKS.
CN - E
CN - D
D25
a
b
c
d
VRS1
CN - A
RY6
(J1)
1
3
5
31
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