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5-5

H. AIR DUCT ASSEMBLY REMOVAL

1) Disconnect the leadwire from lamp.

2) Remove the mounting screw to Latch Board.

I. MAGNETRON REMOVAL

1) Disconnect the leadwire from the high voltage

transformer and high voltage capacitor.

2) Carefully remove the mounting screws holding the

magnetron and the waveguide.

3) Remove the magnetron ASS’Y 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/cm

2

. (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.

J. REMOVING THE TURNTABLE MOTOR

1) Remove the turntable.
2) Remove the Rotating Ring.
3) Lay the unit down on its back.
4) Remove the turntable motor cover.

The turntable base cover is easily removed by

pinching the six parts with a wire cutting.

5) Disconnect the leadwire from the turntable motor

terminals.

6) Remove the screw securing the turntable motor to

the oven cavity ASS’Y

7) After repairing the motor, rotate the removed

turntable motor cover.

8) 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.

Waveguide

Magnetron

Magnetron
Gasket

Magnetron

Dome

Waveguide 
Bracket

Wire Leads

Turntable Motor

Summary of Contents for MB-392A

Page 1: ...ich 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 radi...

Page 2: ...ter 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 possibly c...

Page 3: ...perature is 5 K The microwave power output P in watts is calculated from the following formula 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 ord...

Page 4: ...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 F FAN MOTOR ASSEMBLY REMOVAL 1 Discharge the high voltage capacitor 2 Disconnect the leadwire from fan motor noise filter and high voltage capacitor 3 Remove the two screws holding the the suction guide ASS Y...

Page 5: ... 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 J REMOVING THE TURNTABLE MOTOR 1 Remove the turntable 2 Remove the Rotating Ring 3 Lay the unit down on its back 4 Remove the turntable motor cover The turntable base cover...

Page 6: ...SSEMBLY 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 adjustment Make sure that the latch moves sm...

Page 7: ... 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 op...

Page 8: ...S TEST PROCEDURE RESULTS HIGH VOLTAGE TRANSFORMER Wire leads removed MAGNETRON Wire leads removed 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 1 Measure the resistance Ohm meter scale Rx1 Filament terminal 2 Measure the resistance Ohm met...

Page 9: ...r scale Rx1000 Terminal to case Measure the continuity Forward Ohm meter scale Rx10000 Measure the continuity Reverse Ohm meter scale Rx10000 Normal Momentarily indicates several ohms and then gradually returns to infinite Normal Normal Continuity Abnormal Normal Abnormal Continuity NOTE When testing the magnetron be sure to install the magnetron gasket in the correct position and be sure that the...

Page 10: ...e replacing the fuse If the fuse is blown by improper switch operation replace the defective switch and the fuse at the same time Replace just the fuse if the switches operate normally NOTE Make sure heater is fully cooled when tested Measure the resistance Multi meter scale Rx1 Normal Grill heater Approx 50 Ω at 20 30 C Normal more than 200 MΩ Normal Abnormal Measure the resistance with 500V 100M...

Page 11: ...scale R x 1000 Normal Abnormal or several Ω Normal Approx 100 200 Ω Abnormal or several Ω 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 A B C Turn On Turn Off A B Grill Switch Microwave Switch Approx 22 KΩ No...

Page 12: ...el to discharge any static charge built up in your body CONDITION Microwave oven does not work Inserting many plug into one plug outlet and using them at the same time causes overloading Microwave oven plug is not inserted tightly Output power is too low Low AC input voltage Food temperature is too low Using metallic ware and allowing it to touch the oven wall Sparks occurring Inconsistent intensi...

Page 13: ...ned Disconnect one side of the wire lead connected from transformer to the high voltage capacitor and operate the unit Replace fuse 1 Oven does not operate No continuity No continuity Adjust or replace Malfunction of the primary switch Malfunction of the secondary switch Adjust or replace Check the continuity of the primary switch with door closed Check the continuity of the secondary switch with ...

Page 14: ...ician Check the power source voltage oscillating No continuity No continuity replace Malfunction of the timer switch Faulty thermostat replace Check the continuity of the timer switch contacts Check the continuity of the thermostat CONDITION CHECK RESULT CAUSE REMEDY TROUBLE 4 Grill CONDITION CHECK RESULT CAUSE REMEDY 1 Heater is not operating Abnormal Normal Normal Heater Thermostat Grill Abnorma...

Page 15: ...oking state Check the monitor resistor Abnormal Defective AC relay Replace Normal Check the AC relay Abnormal Open the secondary winding of the high voltage transformer of faulty insulation of filament winding Replace Check H V transformer Abnormal Shorted H V diode Replace Check H V diode Abnormal Faulty capacitor Replace Check H V capacitor Abnormal Faulty magnetron Replace Magnetron TROUBLE 5 O...

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