R-82STM (serv.man2) — Sharp Home Appliance Service Manual (repair manual)

Model
R-82STM (serv.man2)
Pages
27
Size
765.06 KB
Type
PDF
Document
Service Manual
Brand
Device
Home Appliance / Microwave Oven
File
r-82stm-sm2.pdf
Date

View Sharp R-82STM (serv.man2) Service Manual online

82STM -
1
SERVICING
AFTER REPAIR 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.
When all service work is completed, and the oven is fully assembled, the microwave power output should be checked
and microwave leakage test carried out.
 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, High voltage wires.
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 high-voltage capacitor (that is, of the connecting lead of the high-
voltage rectifier) against the chassis using a screwdriver with an insulated handle.
Sharp recommend that wherever possible, fault-finding is carried out with the supply disconnected.  In some cases, it
may be necessary to connect the supply with  the cover removed to carry out fault investigation in the control circuitry.
In such cases, the high voltage circuit should be disabled as described below to reduce the hazards:-
Carry out 3D checks (see above).
Disconnect the supply leads from the high voltage transformer, making a note of the polarity.  Insulate the
connectors, ensuring they are positioned away from the transformer and fastened there.
Connect any relevant test equipment e.g. voltmeter.
Reconnect the oven to the supply, then close the door.
Note the results of the test, taking care to keep clear of the operational oven.
Carry out 3D checks (see above).
Reconnect the leads to the transformer.  Take care to observe correct polarity.
Carry out 4R checks (see below).
Microwave ovens should not be used without a load.   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 microwave timer for one (1) minute, set the
power level to HIGH (100%) and push the start key. When the one (1) minute has elapsed (timer at zero) carefully check
that the water is now hot.
IMPORTANT:
If the oven becomes inoperative because of a blown fuse F8A Fuse, check the monitored latch switch
and monitor switch before replacing the fuse F8A.
WARNING: WIRING / RE-WIRING
Before carrying out any work; carry out 3D checks.
1) Disconnect the supply.
2) Open the door and wedge open.
3) Discharge the high voltage capacitor.
RE-WIRING
1) Wires must not touch:
a) High voltage parts.
b) Parts that become hot.
c) Sharp edges.
d) Movable parts.
2) Positive lock connectors are fitted correctly
3) Wires are connected correctly as per pictorial diagram.
4) No wire leads are trapped by the outer wrap.
82STM - 2
WARNING
Servicing and repair work must be carried out only by
trained service engineers.
The parts marked '*' on the parts list and schematic
diagram have voltages in excess of 250V.
Removal of the outer wrap gives access to potential
above 250V.
All the parts marked "
∆" on the parts list may cause undue
microwave exposure, by themselves, or when they are
damaged, loosened or removed.
CAUTION
MICROWAVE RADIATION
Do not become exposed to radiation from the
magnetron or other parts conducting microwave
energy.  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.
CAUTION / WARNING
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
If the mains lead is replaced, only part number QACCBA004URE1 should be used
OVEN
APPEARANCE VIEW
nfo
MICRO
Lbs Kg Oz AUTO
COOK
%
1
2
3
4
5
8
7
6 10
9
10
12
11
1.
Grill heating element (top grill)
2.
Oven lamp
3.
Control panel
4.
Door opening button
5.
Waveguide cover
6.
Oven cavity
7.
Turntable motor shaft
8.
Grill heating element (bottom grill)
9.
Door seals
10.
Air-vent openings
11.
Outer cabinet
12.
Power cord
82STM -
3
ITEM
DESCRIPTION
Power Requirements
230 - 240 Volts / 50 Hertz / Single phase, 3 wire earthed
Power Consumption
Microwave cooking                          1.45kW Approx. 6.2A
Dual cooking
(Microwave and Top Grill)
2.65kW Approx. 11.2A
(Microwave and Bottom grill)            2.25kW Approx. 9.4A
(Microwave and Convection)
2.65kW Approx. 11.2A
(Top and Bottom Grill)                      2.05kW Approx. 8.4A
Convection cooking                          2.08kW Approx. 9.1A
Grill Cooking
(Top Grill)
1.25kW Approx. 5.2A
(Bottom Grill)                                          0.85kW Approx. 3.4A
Power Output
900 watts nominal of RF microwave energy (measured by method of IEC
705) Operating fequency 2450 MHz
Grill heating element Power Output
Top Grill 1.2kW (600W x 2)
Bottom Grill 0.8kW
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
325mm
Control Complement
Touch Control System
Microwave Cooking Control
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
WEIGHT keys, INFO key
CONVENIENCE FOODS key
PIZZA key, AUTO COOK key
AUTO DEFROST key
LESS(
)/MORE(
)
DUAL COOK, GRILL, MICROWAVE, CONVECTION
MINUTE TIMER
CLOCK SETTING key
STOP key
AUTO MINUTE/START
TIME key (10 MIN., 1MIN., 10 SEC.)
Set Weight
Approx. 20 kg
SPECIFICATION
PRODUCT DESCRIPTION
82STM - 4
OFF CONDITION
Closing the oven door activates all door interlock switches
(monitored latch switch and stop switch).
IMPORTANT:
When the oven door is closed, the contacts COM-NC of the
monitor switch SW2 must be open and the contacts (COM-
NO) must be closed. When the microwave oven is plugged
in a wall outlet (230-240V / 50Hz), 230-240 volts A.C. is
supplied to the point A1 + A3 in the control unit.
1. The display starts demo mode.
2. To set any programmes or set the clock, you must first
touch the STOP key.
3. Information appears on display.
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 Time keys and start the
oven with touching START key.
Function sequence Figure O-1 on page 17
CONNECTED COMPONENTS
RELAY
Oven lamp, Turntable motor
RY1
High voltage transformer
RY2
Fan motor
RY5
1
When the cooking time is up, a signal tone is heard and
the relays RY1 + RY2 + RY5 go back to their home
position. The circuits to the oven lamp, high voltage
transformer, fan motor and turntable motor are cut off.
2. When the oven door is opened during a cooking cycle,
the switches come to the following condition.
Switch
Contact
          Condition
During
Oven Door
Cooking
Open(No cooking)
 Monitored latch Switch COM-NO
Closed
Opened
 Monitor Switch
COM-NO
Closed
Opened
 Monitor Switch
COM-NC
Opened
Closed
Stop switch
COM-NO
Closed
Opened
The circuit to the high voltage transformer, is cut off when the
contact of relay RY2 contacts COM-NO of the monitored
latch switch SW1, and monitor switch SW2 are made open.
The circuit to the fan motor is cut off when the relay RY5 is
made open. The circuit to the turntable motor is cut off when
the contacts COM-NO of the monitor switch are made open.
The relay RY2 and RY5 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.
3. MONITOR SWITCH CIRCUIT
The monitor switch SW2 is mechanically controlled by
the oven door, and monitors the operation of the monitored
latch switch SW1.
3-1. When the oven door is opened during or after the cycle
of a cooking program, the monitored latch switch SW1
and stop switch SW3 must open their contacts (COM-
NO) first. After that the contacts (COM-NC) of the
monitor switch SW2 can be closed and the contacts
(COM-NO) of monitor switch SW2 are made open.
3-2. When the oven door is closed. The contacts (COM-NC)
of the monitor switch SW2 must be opened and the
contacts (COM-NO) of monitor switch SW2 must be
closed. After that the contacts of the monitored latch
switch SW1 and the stop switch SW3 are made closed.
3-3. When the oven door is opened and the contacts of the
monitored latch switch SW1 remain closed, the fuse F2
F8A will blow. Because the relay RY1 and monitor
switch SW2 are closed  and a short circuit is caused.
3 seconds  are needed for heating up the
magnetron filament.
32 sec. ON
24 sec. ON
18 sec. ON
12 sec. ON
6 sec. ON
8 sec. OFF
14 sec. OFF
20 sec. OFF
28 sec. OFF
HIGH
MEDIUM
 HIGH
MEDIUM
MEDIUM 
LOW
LOW
Approx. 70%
Approx. 50%
Approx. 30%
Approx. 10%
Approx. 100%
MEDIUM HIGH, MEDIUM, MEDIUM LOW, LOW
COOKING
When the microwave oven is preset for variable cooking
power, the 230-240 volts A.C. power 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.
Note: The On/Off time ratio does not exactly correspond to
the percentage of microwave power, because approx.
Approx 100%
OPERATION SEQUENCE
82STM -
5
OPERATION SEQUENCE
SENSING FIRE OPERATION
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 measure-
ment circuit intermittently within a 32-second time base once
the oven is started in the microwave cooking mode. The oven
will stop its operation when the difference of the voltages is
more than 0.69 volts in microwave cooking condition.
1. Within a 32-second base, first the thermistor is energized
for 3 seconds.  After 2 seconds since the thermistor is
energized, the voltage across the temperature
measurement circuit is measured. And after 21 seconds
since the thermistor is cut off, the convection motor
operates for 10 seconds.
2. The oven carries out the procedure above again. If the
second voltage is 0.69V higher than the first voltage, LSI
judges it is a fire in the oven cavity and stops the oven.
3. When sensor cooking, the sensing fire operation is not
carried out until the oven senses the steam from food.
Because food cannot be cooked well by rotating the
convection fan at that time. After sensing the steam, the
sensing fire operation is started.
CONVECTION
MOTOR
THERMISTOR
Sensing 
Voltage
ON
OFF
ON
OFF
ON
OFF
0 2
20
30 32
64 (sec.)
3 sec.
Sensing the voltage across temperature measurement circuit.
4. When LSI judges it is fire in the oven cavity, LSI will switch
off the relays to the power transformer, fan motor and
convection motor and LSI stops counting down. And then
the damper is closed so that the fresh air does not come
into the oven cavity.
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).
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 IEC-705 test method must be used.
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:
R.F. Power Output = (T2 - T1) x 80.
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/m
(equivalent to 5mW/cm
2
), 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 the National Physical Laboratories are
used.
Suitable leakage detectors :
CELTEC A100
APOLLO X1
OUTPUT POWER TEST PROCEDURE

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