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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

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/cm
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/cm
2
. Always start measuring of an unknown field
to assure safety for operating personnel from radiation
leakage.

SERVICE INFORMATION

2
and should
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(3
• 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)
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
( 1in/sec)
5-1
1 /2
in.)

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Summary of Contents for LG MB-392A

  • Page 1: Service Information

    SERVICE INFORMATION TOOLS AND MEASURING INSTRUMENTS NECESSARY TOOLS NECESSARY MEASURING INSTRUMENTS Tools normally used for TV servicing are sufficient. • TESTER(VOLTS-DC, AC., Ohmmeter) Standard tools are listed below. • Microwave survey meter • Diagonal pliers - Holaday HI-1500 • Long nose pliers HI-1501 •...
  • Page 2: Measurement With Outer Case Removed

    MEASUREMENT WITH OUTER CASE NOTES WHEN MEASURING REMOVED • Do not exceed meter full scale deflection. • The test probe must be removed no faster than • When you replace the magnetron, measure for 1 inch/sec (2.5 cm/sec) along the shaded area, microwave energy leakage before the outer case is otherwise a false reading may result.
  • Page 3: Measurement Of Microwave Power Output

    MEASUREMENT OF MICROWAVE POWER OUTPUT • Microwave power output measurement is made with • The microwave power output P in watts is calculated the microwave oven supplied at its rated voltage and from the following formula : operated at its maximum microwave power setting with 4187 X (∆T) + 0.88 X (T ) X M a load of (1000±5) g of potable water.
  • Page 4: Fan Motor Assembly Removal

    D. DOOR GROSS ASSEMBLY REMOVAL E. HIGH VOLTAGE TRANSFORMER 1) Open the door. REMOVAL 2) Remove the choke cover cap very carefully with a 1) Discharge the high voltage capacitor. flat-blade screwdriver. 2) Disconnect the leadwire from magnetron, high voltage CAUTION : Be careful not to damage door seal plate transformer, and capacitor.
  • Page 5: Magnetron Removal

    H. AIR DUCT ASSEMBLY REMOVAL J. REMOVING THE TURNTABLE MOTOR 1) Disconnect the leadwire from lamp. 1) Remove the turntable. 2) Remove the Rotating Ring. 2) Remove the mounting screw to Latch Board. 3) Lay the unit down on its back. 4) Remove the turntable motor cover.
  • Page 6: Interlock System

    K. TIMER MOTOR REMOVAL L. INTERLOCK SYSTEM 1) Remove the control panel assembly from the 1) INTERLOCK MECHANISM cavity. The door lock mechanism is a device which has 2) Remove screws which hold the timer motor to the been specially designed to eliminate completely control panel.
  • Page 7: Interlock Continuity Test

    INTERLOCK CONTINUITY TEST WARNING : FOR CONTINUED PROTECTION AGAINST EXCESSIVE RADIATION EMISSION, REPLACE ONLY WITH IDENTICAL REPLACEMENT PARTS. 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 B.
  • Page 8: Component Test Procedure

    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.
  • Page 9: Test Procedure

    COMPONENTS TEST PROCEDURE RESULTS Antenna Gasket Chassis 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 Measure the resistance. Normal: Momentarily indicates CAPACITOR (Ohm-meter scale: Rx1000) several ohms, and then...
  • Page 10 COMPONENTS TEST PROCEDURE RESULTS FUSE Check for continuity of the fuse with an Normal Abnormal multi-meter. NOTE: If the fuse is blown, check the primary, the secondary, and the monitor switches, H.V.D. and H.V.C. before replacing the fuse. If the fuse is blown by improper switch operation replace the defective switch and the fuse at the same time.
  • Page 11 COMPONENTS TEST PROCEDURE RESULTS TIMER MOTOR Check for continuity of timer motor with an Turn On Turn Off (Wire leads removed) ohm-meter. (Remove wire leads from timer motor) Approx. 22 KΩ Grill Switch Microwave Switch Note : A is timer ON, OFF switch.
  • Page 12: Troubleshooting

    TROUBLE SHOOTING 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.
  • Page 13 (TROUBLE 1) Oven lamp does not turn on when the timer knob is pushed with door closed. CONDITION CHECK RESULT CAUSE REMEDY Malfunction of the Replace fuse, Check continuity 1. Fuse blows. Continuity. monitor switch. primary, monitor of monitor and secondary switch (with switches.
  • Page 14 CONDITION CHECK RESULT CAUSE REMEDY No continuity. Check the Malfunction of the replace. continuity of the timer switch. timer switch contacts. Check the No continuity. continuity of the Faulty thermostat. replace. thermostat. (TROUBLE 3) Output power is low. CONDITION CHECK RESULT CAUSE REMEDY...
  • Page 15 (TROUBLE 5) Oven does not cook at all even though turntable rotates. CONDITION CHECK RESULT CAUSE REMEDY No microwave Replace the power Malfunction of the Check the No continuity. oscillation. control switch. power control power control switch. switch(cooking state). Continuity. Check the Abnormal or burn Defective monitor...

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