3
SERVICE INFORMATION
CIRCUIT DESCRIPTION
GENERAL DETAILS
• The low voltage transformer supplies the
necessary voltage to the micom controller
when the
• When the door is closed, the primary and
secondary switches are ON and the monitor
WHEN SELECTING COOKING
POWER LEVEL AND TIME
• The micom controller memorizes the function
• The time you set appears in the display
• Each indicator light turns on to indicate that
WHEN TOUCHING THE
START PAD
• The coil of the relay is energized by the
• Power input is supplied to the high-voltage
transformer through the fuse to the primary
L
FUSE
TRANSFORMER
RELAY 1
MICOM CONTROLLER
SECONDARY SWITCH
N
MONITOR SWITCH
PRIMARY SWITCH
• The fan motor rotates and cools the
magnetron by blowing air from the intake on
• Air is also directed into the oven to exhaust the
VAC
winding of the high-
VAC is applied to the magnetron to heat
• A high voltage of approximately 2100 VAC 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-
• The negative 4,000 VDC is applied to the
WHEN THE OVEN IS SET AT ANY
LEVEL EXCEPT MAXIMUM
• The micom controller controls the ON-OFF
time of Relay 1 by the applied signal to vary
the average output power of the microwave
WHEN THE DOOR IS OPENED
DURING COOKING
• Both the primary switch and Relay 1 are cut
high-
• ON-OFF of Relay 1 is coupled electrically with
• When the door is opened, the secondary
switch is openedhen the door is closed, the
• As the door is opened, if the contact of
primary switch and Relay 1 and/or secondary
switch fails to open, the fuse opens due
to the large current surge caused by the
monitor switch activation, which in turn stops
L
N
FUSE
TRANSFORMER
RELAY 1
MICOM CONTROLLER
SECONDARY SWITCH
MONITOR SWITCH
PRIMARY SWITCH
TOOLS AND MEASURING INSTRUMENTS
NECESSARY TOOLS
Tools normally used for TV servicing are
• Diagonal pliers
• Long nose pliers
• Phillips screwdriver
• Flat blade screwdriver
• Wrench (size 5 mm)
• Nutdriver (size 5 mm)
• Adjustable wrench
• Soldering iron
• Solder
• Vinyl insulation tape
• Polishing cloth
NECESSARY MEASURING
INSTRUMENTS
• TESTER (VDC, VAC, ohmmeter)
• Microwave survey meter
- Holaday HI-1500
HI -1501
- Narda 8100
8200
• Inch scale
• 600 cc beaker made of non-conductive
material (glass or plastic) with inside diameter
• Cylindrical vessel made of borosilicate glass,
- outside diameter: approximately 190 mm
- height: approximately 90 mm
• Glass thermometer: 100°C or 212°F
(1 degree scale)
MICROWAVE LEAKAGE TEST
CAUTION
• Be sure to check microwave leakage before
servicing the oven if the oven is operative
prior to servicing.
• Service personnel should inform the
manufacturer, importer, or assembler of
any certied oven unit found to have a
microwave emission level in excess of 5
mW/cm
2
and should repair any unit found to
have an excessive emission level at no cost
ascertain the cause of the excessive leakage
and instruct the owner not to use the oven until
it is working properly and its emission level is
• If the oven operates with the door open, the
service personnel should:
• The service personnel should check all surface
• Check for microwave leakage after servic
The power density of the microwave radiation
leakage emitted by the microwave oven should
not exceed 4 mW/cm
2
the safety of operating
MEASURING MICROWAVE
ENERGY LEAKAGE
• Pour 275 ± 15 cc of 20 ± 5°C (68 ± 9°F) water
in a beaker graduated to 600 cc and place
the beaker on the center of the turntable.
• Set the energy leakage monitor to 2450
MHz and test energy leakage, following
the test procedures recommended by the
manufacturer.
• When measuring the leakage, always use the
2 in (5 cm) spacer supplied with the probe.
• Operate the oven at its maximum output.
• Measure the microwave radiation using
an 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/second
(1 in/second)
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