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MICROWAVE OVEN SERVICE MANUAL
MODEL : MS-3942FB
CAUTION
BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
SAFETY PRECAUTIONS
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.
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 open. B) Make the following safety checks on all ovens to be serviced before activating the magnetron or other microwave source, and make repairs as 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, (5) evidence of dropping or abuse. C) Before turning on microwave power for any service test or inspection within the microwave generating compartments, 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 CSA should be performed on each oven prior to release to the owner.
CONTENTS
(Page)
SAFETY PRECAUTIONS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Inside front cover SPECIFICATIONS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1-1 CAUTIONS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2-1 INSTALLATIONS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3-1 OPERATING INSTRUCTIONS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4-1
FEATURES- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4-1 CONTROL PANEL - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4-1 OPERATING SEQUENCE- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4-2 SCHEMATIC DIAGRAM - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4-3 CIRCUIT DESCRIPTION - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4-4
SERVICE INFORMATION - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5-1
TOOLS AND MEASURING INSTRUMENTS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5-1 MICROWAVE LEAKAGE TEST - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5-1 MEASUREMENT OF MICROWAVE POWER OUTPUT - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5-3 DISASSEMBLY AND ADJUSTMENT - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5-3 INTERLOCK CONTINUITY TEST- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5-7 COMPONENT TEST PROCEDURE - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5-8 TROUBLE SHOOTING - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5-11
EXPLODED VIEW - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 6-1 REPLACEMENT PARTS LIST - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 7-1 SCHEMATIC DIAGRAM OF P.C.B. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 8-1
PRINTED CIRCUIT BOARD - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 8-2
P.C.B. PARTS LIST - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 9-1
SPECIFICATIONS
ITEM
MODEL
Power Requirement
DESCRIPTION
MS-3942FB
230/240 Volts AC 60 Hz 1,500 Watts (13.0 A) Single phase, 3-wire grounded
Power Output Microwave Frequency Magnetron Timer Outside Dimensions Cavity Dimensions Net Weight Shipping weight Control Complement
1,100 Watts full microwave power (IEC705) 2,450 MHz 2M248 0 ~ 99 min. 99 sec. 556 (W) x 321 (H) x 439 (D) 377 (W) x 251 (H) x 405 (D) 16.7 kg (approx.) 18.3 kg (approx.) Touch Control System Clock : 1:00 - 12:59 Microwave Power for Variable Cooking Power level HIGH ----------------------------------------Full power throughout the cooking time 9 (Saute) -------------------------approx. 90% of Full power, 7 (Med.-High) --------------------approx. 70%, 5 (Med.-Low) --------------------approx. 50%, 3 (Low) ---------------------------approx. 30%, 1 (Warm)--------------------------approx. 10% 8 (Reheat) --------approx. 80% 6 (Medium) --------approx. 60% 4 (Defrost) ---------approx. 40% 2 (Simmer)--------approx. 20%
Nameplate Location
Back Side
Accessories
Owner's manual & cooking guide Glass turntable Rotating ring
This microwave oven is designed for household use only. It is not recommended for commercial purposes.
1-1
CAUTIONS
Unlike other appliances, the microwave oven is high-voltage and high-current equipment. Though it is free from danger in ordinary use, extreme care should be taken during repair.
· DO NOT operate on a 2-wire extension cord during repair and use. · NEVER TOUCH any oven components or wiring during operation. · BEFORE TOUCHING any parts of the oven, always remove the power plug from the outlet. · For about 30 seconds after the oven stops, an electric charge remains in the high voltage capacitor. When replacing or checking, you must discharge the high voltage capacitor by shorting across the two terminals with an insulated screwdriver.
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 connection. All input and output microwave connections, waveguide, flange, and gasket must be secure never operate the device without a microwave energy absorbing load attached. Never look into an open waveguide or antenna while the device is energized. · Proper operation of the microwave oven requires that the magnetron be assembled to the waveguide and cavity. Never operate the magnetron unless it is properly installed. · Be sure that the magnetron gasket is properly installed around the dome of the tube whenever installing the magnetron.
ANTENNA
Gasket
COOLING FIN FILAMENT TERMINALS MAGNETRON CHASSIS GROUND
· Remove your watches whenever working close to or replacing the Magnetron. · DO NOT touch any parts of the control panel circuit. A resulting static electric discharge may damage this P.C.B. · NEVER operate the oven with no load. · NEVER injure the door seal and front plate of the oven cavity. · NEVER put iron tools on the magnetron. · NEVER put anything into the latch hole and the interlock switches area.
MAGNETRON
THE OVEN IS TO BE SERVICED ONLY BY PROPERLY QUALIFIED SERVICE PERSONNEL.
2-1
INSTALLATIONS
BEFORE YOU BEGIN, READ THE FOLLOWING INSTRUCTIONS COMPLETELY AND CAREFULLY.
INSTALLING
1. Empty the microwave oven and clean inside it with a soft, damp cloth. Check for damage such as misaligned door, damage around the door or dents inside the cavity or on the exterior. 2. Put the oven on a counter, table, or shelf that is strong enough to hold the oven and the food and utensils you put in it. (The control panel side of the oven is the heavy side. Use care when handling.) 3. Do not block the vent and the air intake openings. Blocking vent or air intake openings can cause damage to the oven and poor cooking results. Make sure the microwave oven legs are in place to ensure proper air flow. 4. The oven should not be installed in any area where heat and steam are generated, because they may damage the electronic or mechanical parts of the unit. Do not install the oven next to a conventional surface unit or above a conventional wall oven. 5. Use microwave oven in an ambient temperature less than 104°F(40°C). 6. Place the microwave oven on a sturdy and flat surface at least 10 cm(4 inches) from the wall. 7. Place the microwave oven as far away as possible from TV, RADIO, COMPUTER, etc., to prevent interference.
EARTHING INSTRUCTIONS
This microwave oven is designed to be used in a fully earthed condition. It is imperative, therefore, to make sure it is properly earthed before servicing
WARNINGTHIS APPLIANCE MUST BE EARTHED
IMPORTANT
The wires in this mains lead are colored in accordance with the following code: Green-and-yellow: Blue: Brown: Earth Neutral Live
As the colors of the wires in the mains lead of this appliance may not correspond with the colored markings identifying the terminals in your plug, proceed as follows. The wire which is colored 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 colored green or green-and-yellow. The wire which is colored blue must be connected to the terminal in the plug which is marked with the letter N or colored black. The wire which is colored brown must be connected to the terminal in the plug which is marked with the letter L or colored red.
10cm
3-1
OPERATING INSTRUCTIONS
FEATURES
Oven Front Plate Window Door Screen Door Seal Display Window Control Panel
Safety Door Lock System Turntable Rotating Ring
CONTROL PANEL
1. DISPLAY WINDOW. 2. AUTO REHEAT: This feature provides you with the best cooking method by selecting menu. 3. AUTO COOK: This feature provides you with the best cooking method by selecting menu. 4. MORE / LESS: All of the one touch cook and TIMED COOK can be adjusted to cook food for a longer or shorter time. MORE LESS Pressing MORE will add 10 seconds to the cooking time. Pressing LESS will subtract 10 seconds of cooking time.
! # $
5. QUICK DEFROST: This feature provides you with the quick defrosting method for 0.5kg of beef. 6. AUTO DEFROST: This feature provides you with the best defrosting method for frozen foods. 7. NUMBER: These used to set for time of day, cooking time, power level, or defrost weight. 8. POWER: You can select the desired power level for cooking. 9. CLOCK: It is used to set the time of day. 10. STOP/CLEAR: It used to stop oven and clear all entries except time of day.
" % '
&
11. START: This feature allows oven to begin functioning.
4-1
OPERATING SEQUENCE
The following is a description of component functions during oven operation.
1. SETTING THE CLOCK
STOP/CLEAR CLOCK NUMBER CLOCK
6 AUTO DEFROST COOKING
STOP/CLEAR
AUTO DEFROST NUMBER OF WEIGHT
START
ex.) To set 4:30, touch number key [4],[3], and [0]. NOTE: 1) This is a 12 hour clock. 2) Clock will operate as long as power is applied to the oven.
7. CHILD LOCK
This oven has a CHILD LOCK feature TO SET CHILD LOCK · Touch the STOP/CLEAR pad · Touch and hold 0 pad LOCK appear on the display. TO CANCEL CHILD LOCK · Touch and hold 0 pad disappears.
2. CANCEL FUNCTION
Touch the STOP/CLEAR pad whenever you need to cancel an entry or a function currently in use. The display will either return to the last item entered or to the clock.
LOCK
3. ONE TOUCH COOKING
STOP/CLEAR PIZZA NOTE: Heat only 1 package at a time.
8. MORE / LESS
The cook time is adjustable by MORE pad or LESS pad STOP/CLEAR COOKING COOKING MORE LESS
4.TIME COOKING
STOP/CLEAR NUMBER NUMBER START POWER STOP/CLEAR
5. MULTI-STAGE COOKING
1ST STAGE
STOP/CLEAR NUMBER POWER NUMBER
2ND STAGE
NUMBER POWER NUMBER START
4-2
SCHEMATIC DIAGRAM
4-3
CIRCUIT DESCRIPTION
GENERAL DETAILS
· The low voltage transformer supplies the necessary voltage to the micom controller when power cord is plugged in. · When the door is closed, the primary switch is ON, the secondary switch is ON, and the monitor switch opens (contact COM and NO). · A high voltage of approximately 2100 volts AC is generated in the secondary of the high voltage transformer which is increased by the action of the high voltage diode and charging of the high voltage capacitor. · The negative 4,000 Volts DC is applied to the filament of the magnetron.
WHEN SELECTING COOKING POWER LEVEL AND TIME
· The micom controller memorizes the function you set. · The time you set appears in the display window. · Each indicator light turns on to indicate that the stage has been set.
WHEN THE OVEN IS SET AT ANY LEVEL EXCEPT MAXIMUM.
· The micom controller controls the ON-OFF time of relay 2 by the applied signal to vary the average output power of microwave oven as POWER LEVEL. (refer to page 1-1) · One complete cycle of relay 2 is 22 seconds.
WHEN TOUCHING THE START PAD
· The coil of the relay is energized by the micom controller. · Power input is supplied to the high voltage transformer through the fuse to the primary switch and relay 2. · Turntable rotates.
WHEN THE DOOR IS OPENED DURING COOKING
· Both the primary switch and relay 2 cut off the primary winding voltage of the high voltage transformer. · ON-OFF of relay 2 is coupled electrically with opening and closing of the secondary switch. · When the door is opened, the secondary switch is opened and when the door is closed, the secondary switch is closed. · The cooking time stops counting down. · Relay stops functioning. · As the door is opened, if the contact of primary switch and relay2 and/or secondary switch fail to open, the fuse opens due to the large current surge caused by the monitor switch activation, which in turn stops magnetron oscillation.
N
MONITOR SWITCH H.V. TRANSFORMER
L L
FUSE
PRIMARY SWITCH RELAY 2
SECONDARY SWITCH
MICOM CONTROLLER
N
MONITOR SWITCH H.V. TRANSFORMER
· The fan motor rotates and cools the magnetron by blowing the air (coming from the intake on the baseplate). · The air is also directed into the oven to exhaust the vapor in the oven through the upper plate. · Cooking time starts counting down. · 3.3 volts AC is generated from the filament winding of the high voltage transformer. This 3.3 volts is applied to the magnetron to heat the magnetron filament through two noise-preventing choke coils.
L L
FUSE
PRIMARY SWITCH RELAY 2
SECONDARY SWITCH
MICOM CONTROLLER
4-4
SERVICE INFORMATION
TOOLS AND MEASURING INSTRUMENTS
NECESSARY TOOLS
Tools normally used for TV servicing are sufficient. Standard tools are listed below. · Diagonal pliers · Long nose pliers · Phillips screwdriver · Flat blade screwdriver · Wrench (size 5mm) · Nutdriver (size 5mm) · Adjustable wrench · Soldering iron · Solder · Vinyl insulation tape · Polishing cloth
NECESSARY MEASURING INSTRUMENTS
· TESTER (VOLTS-DC, AC, Ohmmeter) · Microwave survey meter - Holaday HI-1500 HI-1501 - Narda 8100 8200 · Inch scale · 600 cc non conductive material beaker (glass or plastic), inside diameter: approx. 8.5 cm (31/2 in.) · Cylindrical and made of borosilicate glass vessel. max. thickness: 3 mm outside diameter: approx. 190mm height: approx. 90mm · Glass thermometer: 100°C or 212°F (1 deg scale)
MICROWAVE LEAKAGE TEST
CAUTIONS
· Be sure to check microwave leakage prior to servicing the oven if the oven is operative prior to servicing. · The service personnel should inform the manufacture importer, or assembler of any certified oven unit found to have a microwave emission level in excess of 5 mW/cm2 and should repair any unit found to have excessive emission levels at no cost to the owner and should ascertain the cause of the excessive leakage. The service personnel should instruct the owner not to use the unit until the oven has been brought into compliance. · If the oven operates with the door open, the service personnel should: - Tell the user not to operate the oven. - Contact the manufacturer. · The service personnel should check all surface and vent openings for microwave leakage. · Check for microwave leakage after every servicing. The power density of the microwave radiation leakage emitted by the microwave oven should not exceed 4 mW/cm2. Always start measuring of an unknown field to assure safety for operating personnel from radiation leakage.
MEASURING MICROWAVE ENERGY LEAKAGE
· Pour 275±15cc of 20±5°C (68±9°F) water in a beaker which is graduated to 600 cc, and place the beaker on the center of the turntable. · Set the energy leakage monitor to 2,450 MHz and use it following the manufacturer's recommended test procedure to assure correct result. · When measuring the leakage, always use the 2-inch (5cm) spacer supplied with the probe. · Operate the oven at its maximum output. · Measure the microwave radiation using and electromagnetic radiation monitor by holding the probe perpendicular to the surface being measured Move probe along shaded area Probe scanning speed Less than 2.5 cm/sec (1 in/sec)
5-1
MEASUREMENT WITH OUTER CASE REMOVED
· When you replace the magnetron, measure for microwave energy leakage before the outer case is installed and after all necessary components are replaced or adjusted. Special care should be taken in measuring the following parts. (Circled area of Fig. below) - Around the magnetron - The waveguide
NOTES WHEN MEASURING
· Do not exceed meter full scale deflection. · The test probe must be removed no faster than 1 inch/sec (2.5 cm/sec) along the shaded area, otherwise a false reading may result. · The test probe must be held with the grip portion of the handle. A false reading may result if the operator's hand is between the handle and the probe. · When testing near a corner of the door, keep the probe perpendicular to the surface making sure the probe horizontally along the oven surface; this may cause probe damage.
WARNING : AVOID CONTACTING ANY HIGH VOLTAGE PARTS
RECORD KEEPING AND NOTIFICATION AFTER MEASUREMENT
· After adjustment and repair of any microwave energy interruption or microwave energy blocking device, record the measured values for future reference. Also enter the information on the service invoice. · The microwave energy leakage should not be more than 4 mW/cm.sq. after determining that all parts are in good condition, functioning properly and genuine replacement parts which are listed in this manual have been used. · At least once a year, have the electromagnetic energy leakage monitor checked for calibration by its manufacturer.
MEASUREMENT WITH A FULLY ASSEMBLED OVEN
· After all components, including the outer case, are fully assembled, measure for microwave energy leakage around the door viewing window, the exhaust opening, and air inlet openings. · Microwave energy leakage must not exceed the values prescribed below. NOTE: Leakage with the outer case removed less than 5 mW/cm.sq. Leakage for a fully assembled oven (Before the latch switch (primary) is interrupted) with the door in a slightly opened position-less than 2 mW/cm.sq.
5-2
MEASUREMENT OF MICROWAVE POWER OUTPUT
· Microwave power output measurement is made with the microwave oven supplied at its rated voltage and operated at its maximum microwave power setting with a load of (1000±5) g of potable water. · The water is contained in a cylindrical borosilicate glass vessel having a maximum material thickness of 3 mm and an outside diameter of approximately 190mm. · The oven and the empty vessel are at ambient temperature prior to the start of the test. · The initial temperature (T1) of the water is (10±2)°C 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 turntable which is in the lowest position and the microwave power switched on. · The time T for the temperature of the water to rise by a value T of (10±2)° is measured, where T is the time in seconds and T is the temperature rise. The initial and final water temperatures are selected so that the maximum difference between the final water temperature and the ambient temperature is 5°.
· The microwave power output P in watts is calculated from the following formula : P= 4187 x (T) T
is measured while the microwave generator is operating at full power. Magnetron filament heat-up time is not included. (about 3 sec) · The water is stirred to equalize temperature throughout the vessel, prior to measuring the final water temperature. · Stirring devices and measuring instruments are selected in order to minimize addition or removal of heat. WATER LOAD
TURNTABLE
DISASSEMBLY AND ADJUSTMENT
A. OUTER CASE REMOVAL
1) Disconnect the power supply cord from the outlet. 2) Remove the screws from the rear of the case. The outer case must be moved backward to be lifted off. Remove the screw
securing screw
B. POWER SUPPLY CORD
1) Remove the outer case. 2) Disconnect two terminals and remove one screw of the ground terminal.
C. CONTROL PANEL ASSEMBLY
1) Open the door. 2) Disconnect the leadwire from RELAY (RY2) of the PCB SUB ASSEMBLY. 3) Disconnect the leadwire from connector (CN1) of the PCB SUB ASSEMBLY. 4) Lift up and pull out control panel assembly carefully from the cavity. CAUTION: DISCHARGE THE HIGH VOLTAGE CAPACITOR BEFORE SERVICING (refer to page 2-1)
ground screw
Lift up and pull out control panel
5-3
D. PCB ASSEMBLY REMOVAL
1) Remove the control panel assembly from the cavity. (Refer to control panel assembly removal on previous page.) 2) Remove screws which hold the PCB SUB ASSEMBLY to the control panel. 3) Disconnect the flat cable from the PCB SUB ASSEMBLY and take off the PCB SUB ASSEMBLY.
Remove choke cover cap
Control Panel
PCB Sub Asm
Key Membrane
Remove door Door seal plate
E. DOOR MAIN ASSEMBLY REMOVAL
1) Open the door. 2) Remove the choke cover cap very carefully with a flat-blade screwdriver. CAUTION: Be careful not to damage door seal plate by screwdriver. 3) Lift up and push the door. NOTE: 1. After replacing the door, be sure to check that the primary switch, monitor switch, and secondary switch operate normally. 2. After replacing the door, check for microwave energy leakage with a survey meter. Microwave energy must be below the limit of 4 mW/cm. (with a 275 ml water load) 3. When mounting the door assembly to the oven assembly, be sure to adjust the door assembly parallel to the chassis. Also, adjust so the door has no play between the inner door surface and oven frame assembly. If the door assembly is not mounted properly, microwaves may leak from the clearance between the door and the oven.
Spacer
5-4
F. MAGNETRON REMOVAL
1) Disconnect the leadwire from the magnetron. 2) Carefully remove the mounting screws holding the magnetron and the waveguide. 3) Remove the magnetron ASSEMBLY until the tube is clear from the waveguide. NOTE: 1. When removing the magnetron, make sure its dome does not hit any adjacent parts, or it may be damaged. 2. When replacing the magnetron, be sure to install the magnetron gasket in the correct position and be sure that the gasket is in good condition. 3. After replacing the magnetron, check for microwave leakage with a survey meter around the magnetron. Microwave energy must be below the limit of 5 mW/cm2. (With a 275 ml. water load). Make sure that gasket is rigidly attached to the magnetron. To prevent microwave leakage, tighten the mounting screws properly, making sure there is no gap between the waveguide and the magnetron.
G. REMOVING THE TURNTABLE MOTOR
1) Remove the turntable and rotating ring. 2) Lay the unit down on its back. 3) Remove the turntable motor cover. The turntable base cover is easily removed by pinching the eight parts with a wire cutting. 4) Disconnect the leadwire from the turntable motor terminals. 5) Remove the screw securing the turntable motor to the oven cavity ASSEMBLY. 6) After repairing the motor, rotate the removed turntable motor cover. 7) Fit the turntable motor cover's projecting part to the base plate slit. NOTE: 1. Remove the wire lead from the turntable motor VERY CAREFULLY. 2. Be sure to grasp the connector, not the wires, when removing.
Air Duct
Magnetron
Waveguide Dome Waveguide Bracket Magnetron Gasket Magnetron
Turntable Motor
Wire Leads
H. HIGH VOLTAGE TRANSFORMER REMOVAL
1) Discharge the high voltage capacitor. 2) Disconnect the leadwire from magnetron, high voltage transformer, and capacitor. 3) Remove the screw holding the high voltage transformer to the baseplate.
5-5
I. FAN MOTOR ASSEMBLY REMOVAL
1) Discharge the high voltage capacitor. 2) Disconnect the leadwire from fan motor and high voltage capacitor. 3) Remove the two screws holding the the suction guide ASSEMBLY to the oven cavity. 4) Remove the two screws holding the fan motor ASSEMBLY to the suction guide ASSEMBLY.
K. INTERLOCK SYSTEM
1) INTERLOCK MECHANISM The door lock mechanism is a device which has been specially designed to eliminate completely microwave activity when the door is opened during cooking and thus to prevent the danger resulting from the microwave leakage.
ADJUSTMENT DIRECTION
J. HIGH VOLTAGE CAPACITOR AND DIODE REMOVAL
1) Discharge the high voltage capacitor. 2) Disconnect the leadwire from fan motor and high voltage capacitor. 3) Remove the screw holding the suction guide ASSEMBLY to the oven cavity. 4) Remove the screw holding the high voltage capacitor bracket and remove the high voltage diode earth screw.
PRIMARY SWITCH
Fan Motor Assembly
MONITOR SWITCH SECONDARY SWITCH
Suction Guide
H.V. Capacitor H.V. Transformer H.V. Diode
2) MOUNTING OF THE PRIMARY/MONITOR/ SECONDARY SWITCHES TO THE LATCH BOARD 3) INSTALLATION AND ADJUSTMENT OF THE LATCH BOARD TO THE OVEN ASSEMBLY · Mount the latch board to the oven assembly. · Adjust the latch board in the arrow direction so that oven door will not have any play in it when the door is closed. · Tighten the mounting screw. · Check for play in the door by pushing the door release button. Door movement should be less than 0.5 mm. (1/64 inch) Don't push the door release button while making this adjustment. Make sure that the latch moves smoothly after adjustment is completed and that the screws are tight. Make sure the primary, monitor, and secondary switches operate properly by following the continuity test procedure.
5-6
INTERLOCK CONTINUITY TEST
WARNING : FOR CONTINUED PROTECTION AGAINST EXCESSIVE RADIATION EMISSION, REPLACE ONLY WITH IDENTICAL REPLACEMENT PARTS. ALL THESE SWITCHES MUST BE REPLACED AT THE SAME TIME.
TYPE NO. SZM-V 16-FA-63 OR VP-533A-OF FOR PRIMARY SWITCH TYPE NO. SZM-V 16-FA-62 OR VP-532A-OF FOR MONITOR SWITCH TYPE NO. SZM-V 16-FA-63 OR VP-533A-OF FOR SECONDARY SWITCH
A. PRIMARY INTERLOCK SWITCH TEST
When the door release button is depressed slowly with the door closed, an audible click should be heard at the same time or successively at intervals. When the button is released slowly, the latches should activate the switches with an audible click. If the latches do not activate the switches when the door is closed, the switches should be a adjusted in accordance with the adjustment procedure. Disconnect the wire lead from the primary switch. Connect the ohmmeter leads to the common (COM) and normally open (NO) terminal of the switch. The meter should indicate an open circuit in the door open condition. When the door is closed, the meter should indicate a closed circuit. When the primary switch operation is abnormal, make the necessary adjustment or replace the switch only with the same type of switch.
B. SECONDARY INTERLOCK SWITCH TEST
Disconnect the wire lead from the secondary switch. Connect the ohmmeter leads to the common (COM) and normally open (NO) terminals of the switch. The meter should indicate a open circuit in the door open condition. When the door is closed, meter should indicate an closed circuit. When the secondary switch operation is abnormal, make the necessary adjustment or replace the switch only with the same type of switch.
C. MONITOR SWITCH TEST
Disconnect the wire lead from the monitor switch. Connect the ohmmeter leads to the common (COM) and normally closed (NC) terminals of the switch. The meter should indicate closed circuit in the door open condition. When the door is closed, meter should indicate an open circuit. When the monitor switch operation is abnormal, replace with the same type of switch. NOTE: After repairing the door or the interlock system, it is necessary to do this continuity test before operating the oven.
COMPONENTS
SWITCHES (Wire leads removed)
TEST PROCEDURE
Check for continuity of the switch with an Ohm-meter Primary Switch
NO COM
RESULTS
Door open Door closed
Monitor Switch Secondary Switch
NC COM
NO COM
NOTE : After checking for the continuity of switches, make sure that they are connected correctly.
5-7
COMPONENT TEST PROCEDURE
CAUTIONS
1. DISCONNECT THE POWER SUPPLY CORD FROM THE OUTLET WHENEVER REMOVING THE OUTER CASE FROM THE UNIT. PROCEED WITH THE TEST ONLY AFTER DISCHARGING THE HIGH VOLTAGE CAPACITOR AND REMOVING THE WIRE LEADS FROM THE PRIMARY WINDING OF THE HIGH VOLTAGE TRANSFORMER. (SEE PAGE 2-1) 2. ALL OPERATIONAL CHECKS WITH MICROWAVE ENERGY MUST BE DONE WITH A LOAD (1 LITER OF WATER IN CONTAINER) IN THE OVEN.
COMPONENTS
HIGH VOLTAGE TRANSFORMER (Wire leads removed)
TEST PROCEDURE
FILAMENT WINDING TERMINAL
RESULTS
SECONDARY TERMINAL
PRIMARY TERMINAL
1. Measure the resistance. (Ohm-meter scale: Rx1 and Rx100) · Primary winding · Secondary winding · Filament winding 2. Measure the resistance. (Ohm-meter scale: Rx1000) · Primary winding to ground · Filament winding to ground MAGNETRON (Wire leads removed) 1. Measure the resistance. (Ohm-meter scale: Rx1) · Filament terminal 2. Measure the resistance. (Ohm-meter scale: Rx1000) · Filament to chassis
Approx.: 0.8 ~ 1.0 ohm Approx.: 100 ~ 130 ohm Less than: 1 ohm
Normal: Infinite Normal: Infinite
Normal: Less than 1 ohm
Normal: Infinite
5-8
COMPONENTS
TEST PROCEDURE
Antenna Gasket Chassis
RESULTS
Filament
NOTE: When testing the magnetron, be sure to install the magnetron gasket in the correct position and be sure that the gasket is in good condition. HIGH VOLTAGE CAPACITOR Measure the resistance. (Ohm-meter scale: Rx1000) · Terminal to terminal. Normal: Momentarily indicates several ohms, and then gradually returns to infinite.
Measure the resistance. (Ohm-meter scale: Rx1000) · Terminal to case.
Normal: Infinite.
HIGH VOLTAGE DIODE
Measure the continuity (Forward). (Ohm-meter scale: Rx10000)
Normal: Continuity. Abnormal: Infinite.
NOTE : Some inexpensive meters may indicate infinite resistance in both direction.
Measure the continuity (Reverse). (Ohm-meter scale: Rx10000)
Normal: Infinite. Abnormal: Continuity.
5-9
COMPONENTS
RELAY 2
TEST PROCEDURE
Check for continuity of relay 2 with an ohm-meter. (Remove wire leads from relay 2 and operate the unit.) POWER LEVEL 1 2 3 4 5 6 7 8 9 10
RESULTS
Relay 2
FAN MOTOR (Wire leads removed) Measure the resistance. (Ohm-meter scale: R x 1)
4 sec 6 sec 8 sec 10 sec 12 sec 14 sec 16 sec 18 sec 20 sec 22 sec
18 sec 16 sec 14 sec 12 sec 10 sec 8 sec 6 sec 4 sec 2 sec 0 sec
Normal: A: Approx. 120 ~ 320 ohm. B: Approx. 20 ~ 40 ohm.
B
Abnormal: Infinite or several ohm.
A
TURNTABLE MOTOR (Wire leads removed)
Measure the resistance. (Ohm-meter scale: R x 1 )
Normal: Approx.100~150 ohm Abnormal: Infinite or several ohm.
NOTE : · A MICROWAVE LEAKAGE TEST MUST ALWAYS BE PERFORMED WHEN THE UNIT IS SERVICED FOR ANY REASON. · MAKE SURE THE WIRE LEADS ARE IN THE CORRECT POSITION. · WHEN REMOVING THE WIRE LEADS FROM THE PARTS, BE SURE TO GRASP THE CONNECTOR, NOT THE WIRES.
5-10
TROUBLESHOOTING
WHEN YOU GET A COMPLAINT FROM YOUR CUSTOMER, EVALUATE THE COMPLAINT CAREFULLY. IF THE FOLLOWING SYMPTOMS APPLY, PLEASE INSTRUCT THE CUSTOMER IN THE PROPER USE OF THE MICROWAVE OVEN. THIS CAN ELIMINATE AN UNNECESSARY SERVICE CALL.
CAUTIONS
1. Check grounding before checking for trouble. 2. Be careful of the high voltage circuit. 3. Discharge the high voltage capacitor. (See page 2-1) 4. When checking the continuity of the switches or of the high voltage transformer, disconnect one lead wire from these parts and then check continuity with the AC plug removed. To do otherwise may result in a false reading or damage to your meter. 5. Do not touch any part of the circuit on the PCB since static electric discharge may damage this control panel. Always touch yourself to ground while working on this panel to discharge any static charge built up in your body. (Micom model only)
CONDITION
Microwave oven does not work.
CAUSE
Inserting many plugs into one outlet and using them at the same time. (blown fuse or breaker) Microwave oven plug is not inserted tightly.
REMEDY
Avoid using other electrical appliances when you use the microwave oven.
Insert microwave oven plug securely. Use the microwave oven at adequate line voltage. This may not be a defect. It is possible that the food should be cooked for a longer time period. Do not use metallic ware for cooking except that noted in the cooking guide. Do not use any type of cookware with metallic trimming. 1. Use plastic wrap or lid. 2. Stir once or twice while cooking soup, cocoa or milk, etc.
Output power is too low.
Low AC input voltage.
Food temperature is too low.
Sparks occur.
Using metallic ware and allowing it to touch the oven wall. Ceramic ware trimmed in gold or silver powder is used.
Uneven cooking.
Inconsistent intensity of microwave by their characteristics.
5-11
(TROUBLE 1) The following visual conditions indicate a probable defective control circuit.
1. Incomplete segments. · Segment missing. · Partial segment missing. · Digit flickering (NOTE: Slight flickering is normal.) 2. Colon does not turn on or blink. 3. A distinct change in the brightness of one or more numbers in display. 4. One or more digits in the display are not lighting. 5. Display indicates a number different from one touched, for example, key in 5 and 3 appears in the display. 6. Specific numbers (for example 7 or 9) will not display when key pad is touched. 7. Display does not count down with time blinking or up with clock operation. 8. Display obviously jumps in time while counting down. 9. Display counts down too fast while cooking. 10. Each indicator light does not turn on after setting cooking cycle. 11. Display time of day does not reappear when cooking is finished.
CONDITION
1. No input can be programmed.
CHECK
Check the connection between membrane key assembly and PCB assembly. Replace key membrane assembly and check operation.
RESULT
Continuity
CAUSE
Defective PCB assembly. Loose connection. Defective key membrane assembly. Defective PCB assembly.
REMEDY
Replace PCB assembly. Connect them tightly. Replace key membrane assembly. Replace PCB assembly.
No continuity
2. Some inputs cannot be programmed. 3. Display shows a number or figure different from one touched.
Everything works as specified.
Still have trouble.
4. Random programming when touching other pads. 5. Display is fixed at some figure and can not accept any input.
5-12
(TROUBLE 2) Oven does not operate at all, display window does not display any figures, and no input is accepted.
CONDITION
1. Fuse blows.
CHECK
Check continuity of monitor switch (with door closed). Replace fuse Check continuity of primary switch (with door opened).
RESULT
Continuity.
CAUSE
Malfunction of the monitor switch.
REMEDY
Replace fuse, primary, monitor, secondary switches, and RELAY(RY2) of P.C.B Assembly.
No continuity.
Continuity.
Shorted contact at the primary switch.
No continuity.
Replace fuse, primary, monitor, secondary switches, and RELAY(RY2) of P.C.B Assembly. Replace fuse, primary, monitor, secondary switches, and RELAY(RY2) of P.C.B Assembly. Replace high voltage capacitor. Replace high voltage transformer.
Check continuity of secondary switch (with door opened).
Continuity.
Malfunction of secondary switch.
No continuity.
Disconnect one side of the wire lead connected from transformer to the high voltage capacitor and operate the unit.
Normal.
Defective high voltage capacitor. Defective high voltage transformer.
Fuse blows again
NOTE : All these switches must be replaced at the same time. Refer to page 5-7, 5-8
2. Fuse does not blow.
Check continuity of thermostat.
No continuity.
Defective thermostat.
Replace thermostat.
Continuity.
Check continuity of power supply cord.
No continuity.
Defective power supply cord.
Replace power supply cord.
5-13
(TROUBLE 3) Display shows all figures set, but oven does not start cooking while desired program times are set and START pad is touched. CONDITION
1. Setting time does not count down when touching START pad.
CHECK
Check continuity of secondary switch (with door closed).
RESULT
No continuity.
CAUSE
Defective secondary switch.
REMEDY
Replace secondary switch.
Continuity.
Check the connection between CN1 connector and PCB assembly. 2. Fan motor or oven lamp do not turn on. Check fan motor. Check oven lamp.
Continuity
Defective PCB assembly. Loose connection.
Replace PCB assembly. Connect them tightly. Replace fan motor. Replace oven lamp.
No continuity
Abnormal Abnormal Normal
Defective fan motor. Defective oven lamp.
(TROUBLE 4) Oven seems to be operating but little heat is produced in oven load. CONDITION
Output is low
CHECK
Check the power source voltage.
RESULT
Lower than 90% of rating voltage. Normal
CAUSE
Decrease in power source voltage with load.
REMEDY
Suggest customer contact local electric power utility company or qualified electrician. Replace PCB assembly.
Disconnect the wire leads from relay 2 and check on and off time with multitester.
Abnormal
Defective PCB assembly.
Normal
Measure the output power.
Abnormal
Defective magnetron.
Replace magnetron.
NOTE : Simple test of power output-conducted by heating one liter water for one min. if available. Minimum 8.5°C temperature rise is normal condition. 5-14
(TROUBLE 5) No microwave oscillation even though oven lamp and fan motor run. (Display operates properly) CONDITION
No microwave oscillation.
CHECK
Disconnect the wire leads from relay 2 and check continuity of relay 2. (Operate the unit)
RESULT
No continuity.
CAUSE
Defective PCB assembly.
REMEDY
Replace PCB assembly.
Continuity.
Check high voltage transformer
Abnormal
Defective high voltage transformer.
Replace high voltage transformer.
Normal
Check high voltage capacitor.
Abnormal
Defective high voltage capacitor.
Replace high voltage capacitor.
Normal
Check high voltage diode.
Abnormal
Defective high voltage diode.
Replace high voltage diode.
Normal
Check magnetron.
Abnormal
Defective magnetron.
Replace magnetron.
NOTE : · Make sure the wire leads are in the correct position. · When removing the wire leads from the parts, be sure to grasp the connector, not the wires. · When removing the magnetron, be sure to install the magnetron gasket in the correct position and in good condition.
Output is full power when you set lower power level.
Disconnect the wire leads from relay 2 and check continuity relay 2. (Operate the unit)
Abnormal.
Defective PCB assembly.
Replace PCB assembly.
5-15
EXPLODED VIEW
INTRODUCTION
OVEN CAVITY PARTS INTERIOR PARTS DOOR PARTS BASE PLATE PARTS LATCH BOARD PARTS
CONTROL PANEL PARTS
6-1
DOOR PARTS
15006A
13581A 13536A
13552A
13213A
13352A
13720D 14026A
14970A
6-2
CONTROLLER PARTS
24781M
268711 23572A 23550D
WTP018
23506A
6-3
OVEN CAVITY PARTS
33112U
WTT021
33052A WTT020 WTT010
33390G 36549S 35889A
WTP013
6-4
LATCH BOARD PARTS
WSZ085
43501A 56912B
55262A
466001 466003
44510A 43500A 466001
6-5
INTERIOR PARTS
WSZ002 568771 56411A
50FZZA 56930V 34930W WSZ196 54974S 56549F
56201A
WSZ002 55900A WTT037
948503 56324A 50CZZH WSZ002 948502 54810C WSZ002 56201B WTT028 WSZ002
56851D
56901A
6-6
BASE PLATE PARTS
56170D 63302A
63303A
948501 65006B
WSZ002
WTT021
6-7
SCHEMATIC DIAGRAM OF P.C.B.
8-1
PRINTED CIRCUIT BOARD
8-2
P/NO : 3828W5S1580
Aug, 2000 Printed in Korea