DOWNLOAD LG MS-190A Service Manual ↓ Size: 1.64 MB | Pages: 31 in PDF or view online for FREE

• 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 below Fig.)

- Around the magnetron
- The waveguide

• 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 removedless 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.

• 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 possibly
cause probe damage.

• 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.

5-2

• 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)°K 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°K.

• The microwave power output P in watts is calculated

from the following formula :

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.

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.

1) Remove the outer case.
2) Disconnect two terminals, and remove one screw of

the ground terminal.

1) Open the door.
2) Remove the screws for the ground and securing the

control panel.

3) Disconnect the leadwire from RELAY(RY2) of the

PCB SUB ASS’Y.

4) Lift up and pull out control panel assembly carefully

from the cavity.

5) Disconnect the leadwire from connector(CN1) of the

PCB SUB ASS’Y.

(refer to page 2-1)

5-3

WATER LOAD

TURNTABLE

securing screw

P =

Remove the screw

Lift up and pull out control panel

1) Remove the control panel assembly from the

cavity. (Refer to control panel assembly removal
on previous page.)

2) Remove screws which hold the timer motor to the

control panel.

3) Remove the timer motor.
4) Remove the power control knob.

1) Open the door.
2) Remove the choke cover very carefully with a 

flat-blade 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 5 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.

5-4

Release 
Lever

Control Panel

Timer Motor

Power Control 

Knob

Timer Knob

Door Open Button

Button Spring

Remove choke cover 

Spacer

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/cm

2

. (With a 275 ml. water load).

magnetron. To prevent microwave leakage,
tighten the mounting screws properly, making sure
there is no gap between the waveguide and the
magnetron.

5-5

Magnetron

Waveguide

Magnetron
Gasket

Magnetron

Dome

Waveguide 
Bracket

NOTE: Suction Guide Main ASS’Y consists of Latch
Board ASS’Y and Suction Guide ASS’Y. To repair any of
them, should be removed first Suction Guide Main
ASS’Y.

1) Disconnect the leadwire from the high voltage

transformer primary terminal, thermostat, noise filter
ASS’Y, and turn table motor connector.

2) Remove three screws holding the Suction Guide Main

ASS’Y to oven cavity.

3) Open the suction guide cover.

4) Rotate right and pull out Suction Guide Main ASS’Y

from the oven.

Screw

Remove magnetron

Wave guide and magnetron

Remove screw

Open the suction guide cover