Service Manual
Microwave Oven
Model : KOR-4125
DAEWOO ELECTRONICS CO., LTD. OVERSEAS SERVICE DEPT.
PRECAUTIONS TO BE OBSERVED BEFORE AND DURING SERVICING TO AVOID POSSIBLE EXPOSURE TO EXCESSIVE MICROWAVE ENERGY
(a)Do not operate or allow the oven to be operated with the door opened.
(b)Make the following safety checks on all ovens to be serviced before activating the magnetron or other micro-wave source, and make repairs if necessary: (1) Interlock operation, (2) proper door closing, (3) seal and sealing surfaces (arcing, wear, and other damage), (4) damage to or loosening of hinges and latches, and (5) evidence of dropping or abuse.
(c)Before turning on microwave power for any service test or inspection within the microwave generating com-partments, check the magnetron, wave guide or transmission line, and cavity for proper alignment, integrity, and connections.
(d)Any defective or misadjusted components in the interlock, monitor, door seal and microwave generation and transmission systems shall be repaired, replaced, or adjusted by procedures described in this manual before the oven is released to the owner.
(e)A microwave leakage check to verify compliance with the Federal performance standard should be performed on each oven prior to release to the owner.
TABLE OF CONTENTS
PROPER USE AND SERVICE PRECAUTIONS |
3 |
SPECIFICATIONS |
4 |
SCHEMATIC DIAGRAM OF FEATURES |
5 |
INSTALLATION |
6 |
OPERATION |
7 |
MEASUREMENT OF THE MICROWAVE OUTPUT POWER |
8 |
MICROWAVE RADIATION TEST |
9 |
WIRING DIAGRAM |
10 |
CIRCUIT DESCRIPTION |
11 |
PRECATIONS FOR DISASSEMBLY AND REPAIR |
13 |
DISASSEMBLY AND ASSEMBLY |
14 |
INTERLOCK MECHANISM |
19 |
TROUBLE SHOOTING GUIDE |
21 |
COMPONENT TEST PROCEDURE |
23 |
SAFETY INTERLOCK CONTINUITY TEST |
24 |
EXPLODED AND PARTS LIST |
25 |
2
PROPER USE AND SERVICE PRECAUTIONS
CAUTION : This Device is to be Serviced Only by Properly Qualified Service Personnel. Consult the Service Manual for Proper Service Procedures to Assure Continued Safety Operation and for Precautions to be Taken to Avoid Possible Exposure to Excessive Microwave Energy.
1.For Safe Operation
Damage that allows the microwave energy (that cooks or heats the food) to escape will result in poor cooking and may cause serious bodily injury to the operator.
IF ANY OF THE FOLLOWING CONDITIONS EXIST, OPERATOR MUST NOT USE THE APPLIANCE. (Only a trained service personnel should make repairs.)
1)A broken door hinge.
2)A broken door viewing screen.
3)A broken front panel, oven cavity.
4)A loosened door lock.
5)A broken door lock.
The door seal area and oven cavity surface be kept clean.
No grease, soil or spatter should be allowed to build up on these surfaces or inside the oven.
DO NOT ATTEMPT TO OPERATE THIS APPLIANCE WITH THE DOOR OPEN. The microwave oven has concealed switches to make sure the power is turned off when the door is opened. Do not attempt to defeat them. DO NOT ATTEMPT TO SERVICE THIS APPLIANCE UNTIL YOU HAVE READ THIS SERVICE MANUAL.
2.For Safe Service Procedures.
1)If the oven to be serviced is operative, a microwave emission check should be performed prior to servicing the oven.
2)If any ascertained oven unit is found to have excessive emission level 5mW/cm2, the service person should :
(a)inform the manufacturer, importer or assembler,
(b)repair the unit at no cost to the owner,
(c)attempt to ascertain the cause of the excessive leakage,
(d)tell the owner of the unit not to use it until the oven has been brought into compliance.
3)If the oven operates with the door opened, the service person should tell the user not to operate the oven and contact the manufacturer immediately.
CAUTION
MICROWAVE RADIATION
PERSONNEL SHOULD NOT BE EXPOSED TO THE MICROWAVE ENERGY WHICH MAY RADIATE FROM THE MAGNETRON OR OTHER MICROWAVE GENERATING DEVICE 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 IN IT. NEVER LOOK INTO AN OPEN WAVEGUIDE OR ANTENNA WHILE THE DEVICE IS ENERGIZED.
3
SPECIFICATIONS
ITEM |
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SPECIFICATION |
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POWER SUPPLY |
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230V~50HZ, SINGLE PHASE WITH EARTHING |
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POWER CONSUMPTION |
920 W |
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MICROWAVE |
OUTPOWER |
600 W (IEC 705) (FULL MICROWAVE POWER) |
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FREQUENCY |
2450MHz |
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OUTSIDE DIMENSIONS (W X H X D) |
444X235X337mm |
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CAVITY DIMENSIONS (W X H X D) |
265X172X270mm |
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NET WEIGHT |
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APPROX. 12kg |
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TIMER |
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35min. DUAL SPEED |
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POWER SELECTIONS |
5 LEVELS |
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CAVITY VOLUME |
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0.4 Cu. Ft |
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* Specifications subject to change without notice.
444 |
337 |
235 |
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SCHEMATIC DIAGRAM OF FEATURES
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4 |
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9 3 
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5
6
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¤ Safety Interlock System
¤Ł Door Viewing Screen - Allows viewing of food, the screen is designed so that light can pass through, but not the microwave.
¤ØDoor Hook - When the door is closed, it will automatically shut. if the door is opened while the oven is operating, the magnetro will immediately stop operating.
¤ŒOven Cavity
¤ºDoor Seal - Door seal maintains the microwave energy within the oven cavity and prevents microwave leakage.
¤Glass Cooking Tray - Made of special heat resistant glass. Food in a proper receptacle is placed on this tray for cooking.
¤Roller guide - This must always be used for cooking together with the glass cooking tray.
¤Coupler - This fits over the shaft in the center of the oven’s cavity floor. This is to remain in the oven for all cooking.
¤Knob V.P.C - used to select a microwave power level.
¤Knob timer - used in setting cooking time for all functions.
¤æDoor Release Button - By pushing this button the latch system cut off all circuits and stops the oven before the door is opened.
5
INSTALLATION
1. Steady, flat location.
This microwave oven should be set on a steady, flat surface.
2. Leave space behind and side.
All air vents should be kept a clearance. If all vents are covered during operation, the oven may be overheated and, eventually, oven failure caused.
3. Away from radio, and TV sets
Poor television reception and radio interference may be resulted in, if the oven is located close to a TV, Radio, or antenna, feeder and so on.
4. Away from heating appliances and water taps
Keep the oven away from hot air, steam or splash when choosing a place to position it, or the insulation might be adversely affected and breakdowns occur.
5.power supply
•Check your local power source.
This microwave oven requires a current of approximately 5 amperes, 230V 50Hz. use a receptacle that will accept the earth prong.
•Voltage Warning
The voltage used must be the same as specified on this Microwave Oven.
Using a higher voltage may result in a fire or other accident causing oven damage. Using low voltage will cause slow cooking.
We are not responsible for damage resulted from use of this Microwave Oven with a voltage or amperage fruse other than those specified.
•Power supply cord is about 1.0 meters long. Do not use an extension cord.
If the supply cord is damaged, it must be replaced by the manufacturer or its service agent or a similarly qualified person in order to avoid a hazard;
CAUTION : Do not be under any circumstances cut or remove the round earthing prong from this plug.
CAUTION : Maintenance work like the replacing the power cable must be made by a qualified technician of the after-sales-services.
WARNING: This appliance must be earthed.
IMPORTANT
The wires in this main lead coloured in accordance with the following code.
Green-and-yellow |
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Earth |
Blue |
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Neutral |
Brown |
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Live |
As the colours of the wires in the main lead of this appliance may not correspond with the coloured markings identifying the terminals in your plug, proceed as follows:
The wire which is coloured green-and-yellow must be connected to the terminal in the plug which is marked with the letter ‘E’ or by the earth symbol or green-and-yellow.
The wire which is coloured blue must be connected to the terminal which is marked with the letter ‘N’ or coloured white.
The wire which is coloured brown must be connected to the terminal which is marked with the letter ‘L’ or coloured red.
6. Examine the oven after unpacking for any damage such as:
Dents, A misaligned door, Broken door, Dents in cavity.
If any of the above are visible, do not install this oven.
6
OPERATION
1 Connect the main lead to an electrical outlet.
After placing the food in a suitable container, open the oven door and put it on the glass tray. |
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2 The glass tray must always be in place during cooking. |
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3 CLOSE THE DOOR securely. |
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Choose cooking power level by setting V.P.C. |
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4 knob to the desired position. |
NOTE : |
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Refer to cookbook for recommended power |
1. When setting Timer for less than 2 minutes, turn the |
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levles. |
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Timer past 2 minutes and then return to the correct |
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Determine cooking time. Consult cookbook for |
timer position. |
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5 recipe timing. |
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¢”Oven light turns on and cooling fan starts to |
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operate. Microwave cooking starts. |
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30 |
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25 |
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You may open the door while the oven is |
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6 operating. As soon as the door is opened, the |
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safety mechanisms stop the generation of |
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microwave power and the operation of cooking timer.
If you wish to change the time during cooking, simply adjust the Timer to the desired time.
When the timer reaches zero, a bell will ring and 7 the unit will turn off.
¢”Oven light turns off.
If additional cooking time is needed and the door is closed, the oven will automatically start when the Timer is reset.
2.Various clicking noises may be heard when turning the V.P.C. Knob. This is normal and does not affect the operation of your microwave oven.
Variable power cooking
ON and OFF cycle time of mechanicial V.P.C. switch is 30 seconds.
When the V.P.C. knob is set to the desired position and timer knob turns to the desired position, the V.P.C switch has a cycle (ON/OFF time (sec)) listed below.
Variable power setting |
ON/OFF time (SEC) |
POWER |
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(HIGH) |
30/0 |
100% |
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(MED HIGH) |
23.2/6.8 |
77% |
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(MEDIUM) |
16.5/13.5 |
55% |
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(DEFROST) |
9.8/20.2 |
33% |
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(WARM) |
5/25 |
17% |
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7
MEASUREMENT OF THE MICROWAVE OUTPUT POWER
Microwave output power can be checked by indirectly measuring the temperature rise of a certain amount of water exposed to the microwave as directed below.
Procedure
1.Microwave power output measurement is made with the microwave oven supplied at rated voltage and operated at its maximum microwave power setting with a load of 1,000¡ 5cc of potable water.
2.The water is contained in a cylindrical borosilicate glass vessel having a maximum material thickness of 3 mm and an outside diameter of approximately 190 mm.
3.The oven and the empty vessel are at ambient temperature prior to the start of the test. The initial temeprature of the water is 10¡ 2˚C (50¡ 3.6˚F).
It is measured immediately before the water is added to the vessel. After addition of the water to the vessel, the load is immediately placed on the center of the shelf which is in the lowest notmal position.
4.Microwave power is switched on.
Water Load
5. heating time should be exactly 70 seconds. Heating time is measured while the microwave generator is operating at full power.
The filament heat-up time for magnetron is not included.
6.The initial and final water temepratures are selected so that the maximum difference between the ambient and
final water temperatures is 5K.
Tray |
Fig. 14 |
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7. The microwave power output p in watt is calculated from the following formula:
P = 4187 X § T/t
•T is actual temperature rise.
•T is the heating time.
The power measured should be 600W¡ 10.0%
CAUTION :
1.Water load should be measured exactly to 1 liter.
2.Input power voltage should be exactly 230 volts as specified.
3.Ambient temperature should be 20 ¡ 2˚C(68 ¡ 3.6˚F)
8
MICROWAVE RADIATION TEST
WARNING
•Make sure to check the microwave leakage before and after repair or adjustment.
•Always, start measuring of an unknown field to assure safety for operating personnel from microwave energy.
•Do not place your hands into any suspected microwave radiation field unless the safe density level is known.
•Card should be taken not to place the eyes in direct line with the source of microwave energy.
•Slowly approach the unit under test until the radiometer reads an appreciable microwave leakage from the unit under the test.
Procedure
A) Prepare Microwave Energy Survey Meter, 600cc glass beaker, glass thermometer 100˚C or 212˚F.
B) Pour 275 ¡ 15cc of tap water initially at 20 ¡ 5˚C(68 ¡ 9˚F) in the 600cc neaker with an inside diameter of approx. 9.5cm(3.5in).
C)Place it at the center of the tray and set it in a cavity.
D)Close the door and operate the oven.
E)Measure the leakage by using microwave energy survery meter with dual ranges, set to 2450 MHz. - Measured radiation leakage must not exceed the values prescribed below.
•leakage for a fully assembled oven with door normally closed must be less than 4mW/cm2.
- When measuring the leakage, always use the 2 in(5cm) space cone with probe. Hold the probe perpendicular to the cabinet, door. Place the space cone of the
probe on the door, cabinet, door seam, door viewing screen, the exhaust air vents air vents and the suction air vents.
- Measuring should be in a counter-clockwise direction at a rate of 1 inch/sec. If the leakage of the cabinet
door seam is unknow, move the probe more slowly.
-When measuring near a corner of the door, keep the probe perpendicular to the areas making sure the probe end at the base of the cone does not get closer than 2 inches from any metal.
if it does, erronous reading may be resulted.
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