Sharp R-890SLM Service Manual ▷ View online
R-890SLM
5 - 3
3. MICROWAVE AND BOTTOM GRILL (Figure O-5c)
Press MIX button 3 times. And enter the desired cooking time
by rotating the ENCODER dial. And press MICRO POWER
button to set the desired microwave power. When the INSTANT
COOK/START button 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
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
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 simul-
taneously.
POWER OUTPUT
ON TIME
OFF TIME
100%
54 sec.
0 sec.
90%
49 sec.
5 sec.
80%
45 sec.
9 sec.
70%
40 sec.
14 sec.
60%
36 sec.
18 sec.
50%
29 sec.
25 sec.
40%
24 sec.
30 sec.
30%
18 sec.
36 sec.
20%
13 sec.
41 sec.
10%
9 sec.
45 sec.
[6] ON/OFF TIME RATIO
In grill cooking, convection cooking or combi cooking, the top
heater, bottom heater or magnetron operate within a 54 second
time base. The following table is the ON / OFF time ratio at each
power output of the top heaters, bottom heater or magnetron.
[7] AUTO POWER CONTROL OPERATION
The magnetron, top or bottom heating elements, the fan motor or the convection motor will operate in accordance with following
specification.
1. OUTPUT POWER CONTROL (MANUAL COOK)
OPERATION MODE
DEVICE
POWER CONTROL
MICROWAVE (100%)
SINGLE OPERATION
Microwave
100% 20min, then 70%
TOP GRILL (100%)
SINGLE OPERATION
Top heater
100% 15min, then 50%
BOTTOM GRILL (100%)
SINGLE OPERATION
Bottom heater
100% 15min, then 50%
TOP(100%)/BOTTOM(100%)
Top heater
100% 6min then 70% and 70% 9min then 50%
COMBI OPERATION
Bottom heater
100% 6min then 70% and 70% 9min then 50%
MICRO(100%)/TOP GRILL(100%)
Microwave
100% 20min, then 70%
COMBI OPERATION
Top heater
100% 15min, then 50%
MICRO(70 - 10%)/TOP GRILL(100%)
Microwave
-
COMBI OPERATION
Top heater
100% 15min, then 50%
MICRO(100%)/BOTTOM GRILL(100%)
Microwave
100% 20min, then 70%
COMBI OPERATION
Bottom heater
100% 15min, then 50%
MICRO(70 - 10%)/BOTTOM GRILL(100%)
Microwave
-
COMBI OPERATION
Bottom heater
100% 15min, then 50%
Repeat Cook
Microwave
Top heater
Bottom heater
In case same cooking mode is repeated within 1min 15sec
(including stop, end), oven calculates total cooking time and
reduce the power level.
2. OUTPUT POWER CONTROL (AUTO COOK)
OPERATION MODE
DEVICE
POWER CONTROL
Repeat Auto Cook
Microwave
The power level is not reduced 1 time cooking. But only in
case same menu is repeated within 1min 15sec, the power
level of micro and grill is reduced from 100% to 70% in 20mins
after starting of last cooking. (Even if the time of the last cook-
ing is longer than 20mins, the power level isn’t reduced on the
last cooking, and it is reduced from the beginning of the next
cooking.) However, in time calculated from the start of the 1st
cooking, even if the Cook mode changed, when repetition
cooking of the menu with which 100% of top & bottom heaters
continues are performed, as shown in the following table, the
power down of the cooking of the 2nd henceforth is carried
out. (The 1st cooking is not applied)
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3. COOLING FAN OPERATION
OPERATION MODE
DEVICE
POWER CONTROL
PREHEAT
Cooling
60%
CONV. (OVEN)
Cooling fan 60% 60 min. then 100%
Others
Cooling fan 100%
After cooking
Cooling fan A cooling fan continues the rotation when Oven temperature is more than 120°C.
Then, it stops when it is less than 105°C
Indication
NOW COOLING is indicated during the cooling fan movement after operation is
finished. (It isn’t indicated during a fan movement to stop on the way.)
4. CONVECTION POWER SETTING
4.1. PREHEATING
TEMP
250°C, 230°C, 220°C, 200°C, 180°C, 160°C, 130°C, 100°C, 70°C, 40°C
HEATING ELEMENT
TOP
100%
BOTTOM
100%
COOLING FAN
60%
CONV. FAN
0%
4.2. CONVECTION
TEMP
250°C 230°C 220°C 200°C 180°C 160°C 130°C 100°C 70°C
40°C
✩
WITHOUT PREHEATING
HEATING
ELEMENT
TOP
50%
40%
40%
30%
20%
10%
10%
10%
10%
10%
BOTTOM 100% 90%
80%
70%
70%
60%
50%
40%
30%
20%
✩
WITH PREHEATING
HEATING
ELEMENT
TOP
50%
40%
40%
30%
20%
10%
10%
10%
10%
10%
BOTTOM
90%
70%
60%
50%
50%
50%
50%
40%
30%
20%
COOLING FAN
60% 60min, then 100%
CONV. FAN
100%
0%
4.3. COMBI-1 (Micro + Conv)
TEMP
250°C 230°C 220°C 200°C 180°C 160°C 130°C 100°C 70°C
40°C
✩
WITHOUT PREHEATING
HEATING
ELEMENT
TOP
50%
40%
40%
30%
20%
10%
10%
10%
10%
10%
BOTTOM 100% 90%
80%
70%
70%
60%
50%
40%
30%
20%
✩
WITH PREHEATING
HEATING
ELEMENT
TOP
50%
40%
40%
30%
20%
10%
10%
10%
10%
10%
BOTTOM
90%
70%
60%
50%
50%
50%
50%
40%
30%
20%
MICRO
10%, 30%, 50%
COOLING FAN
100%
CONV. FAN
100%
0%
NOTE: ✩The oven temp was checked by the thermometer when each stage is started.
If the oven temp is same or higher than 105°C, the oven was judged as “with preheating”.
When the oven temp is lower than 105°C or the cooling fan stops, the oven was judged as “without preheating”.
Micro and Top heating element can’t be on at the same time.
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CHAPTER 6. FUNCTION OF IMPORTANT COMPONENTS
[1] DOOR OPEN MECHANISM
The door can be opened by pulling the door handle. When the
handle is pulled, the latch head is pulled, the latch head is moved
upward, and released from the latch hook now the door can be
opened.
Figure D-1. Door Open Mechanism
Latch hook
Door
Stop switch
Latch
Heads
Monitor switch
Monitored
latch switch
Tab
[2] SWITCH
1. MONITORED LATCH SWITCH
1. When the oven door is closed, the contacts (COM-NO) of the
switch must be closed. And the contacts (COM-NC) must be
opened.
2. When the oven door is opened, the contacts (COM-NO) of
the switch must be opened. And the contacts (COM-NC)
must be closed.
2. 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 (COM-NO) of
switch must be opened.
3. 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
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 (COM-NC) contacts.
CAUTION: BEFORE REPLACING A BLOWN FUSE F8A,
TEST THE MONITORED LATCH SWITCH AND
MONITOR SWITCH FOR PROPER OPERATION.
(REFER TO CHAPTER “TEST PROCEDURE”).
[3] FUSE
1. FUSE 20A 250V
If the wire harness or electrical components are shortcircuited,
If the wire harness or electrical components are shortcircuited,
this fuse blows to prevent an electric shock or fire hazard.
2. 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.
[4] TC TRANSFORMER
T/C transformer converts A.C. line voltage into low voltage to
drive the control unit.
[5] THERMAL CUT-OUT
1. THERMAL CUT-OUT 125°C (MG)
This thermal cut-out protects the magnetron against overheat.
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.
2. THERMAL CUT-OUT 145°C (OVEN)
This thermal cut-out protects against overheating /fire inside the
This thermal cut-out protects against overheating /fire inside the
oven. The cut-out contacts will open when temperatures exceed
145°C. When the cut-out cools itself down to the operating
temperature of 115°C, the contacts of the thermal cut-out will
close again.
[6] 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 fuse F8A 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 fuse F8A.)
D2
D1
ASYMMETRIC
RECTIFIER
HIGH VOLTAGE
RECTIFIER
1. The high voltage rectifier is shorted by some fault when
microwave cooking or combi cooking.
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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
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 F2 F8A blows by the large electric currents.
7. The power supplying to the high voltage transformer is cut off.
7. The power supplying to the high voltage transformer is cut off.
[7] NOISE FILTER
The noise filter assembly prevents radio frequency interference
that might flow back in the power circuit.
[8] MOTOR
1. TURNTABLE MOTOR
The turntable motor rotates the turntable.
The turntable motor rotates the turntable.
2. FAN MOTOR
The fan motor drives a blade which draws external cool air.
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.
3. CONVECTION MOTOR
The convection motor drives the convection fan and provide the
The convection motor drives the convection fan and provide the
heated air.
[9] HEATING ELEMENT
1. TOP GRILL HEATING ELEMENT
The grill heating element is provided to brown the food and is
The grill heating element is provided to brown the food and is
located on the top of the oven cavity.
2. BOTTOM GRILL HEATING ELEMENT
The grill heating element is provided to brown the food and is
The grill heating element is provided to brown the food and is
located at the base of the oven cavity.
[10] 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
heating elements.
The air heated by the grill heating elements is circulated through
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
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
When the convection time reaches “0”, the heating elements
are de-energized and the convection fan stops operating and
the oven shuts off. At that time if the cavity air temperature has
rised above 120°C, the fan motor remains rotating. Automatically
the fan motor will be shut down at low temperature (less than
105°C).
Figure D-2. Convection Cooking System
Door
Oven Cavity
Grill Heating
Element
Bottom Grill
Heating Element
Convection
Passage
Cooling
Fan
Convection
Motor
Convection
Fan
Turntable
Insulation
Turntable
Motor
[11] 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
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
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 as a
fire in the oven cavity and stop the oven.
3. When LSI judges it as a fire in the oven cavity, LSI will switch
off the relays to high voltage transformer and fan motor and
LSI stops countering down.
THERMISTOR
SENSING
VOLTAGE
ON
OFF
ON
OFF
30
32 (sec.)
Sensing the voltage across temperature measurement circuit.
[12] 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 combi
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.
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