DOWNLOAD LG MB390A Service Manual ↓ Size: 794.87 KB | Pages: 32 in PDF or view online for FREE

Model
MB390A
Pages
32
Size
794.87 KB
Type
PDF
Document
Service Manual
Brand
Device
Microwave Oven
File
mb390a.zip
Date

LG MB390A Service Manual ▷ View online

4-2
OPERATING SEQUENCE
MICROWAVE COOKING
1. Open the oven door, place the food on the
turntable in the oven, and close the oven door.
2. Set the function selector to the microwave.
3. Set the microwave power selector to the desired
power level. There are five power levels from
WARM to HIGH. The power selector can be set to
any one of these positions.
NOTE:
• Each number represents minutes. To ensure
accurate timing, it is advisable to turn the timer knob
slightly passed the desired cooking time and then
back to the proposed setting.
• Press the door opener to check the cooking
condition during oven operation. Opening the door
during oven operation automatically turns off the
oven and stops the timer. If cooking is to continue,
close the door. Cooking will be resumed until the full
cooking time has elapsed.
GRILL COOKING
1. Open the oven door, place the food on the rack in
the oven, and close the oven door.
2. Set the          function.
3. Set the timer to the desired cooking time. The
turntable begins to rotate, cooking starts, and the
lamp is turned on. At the end of the cooking time
you will hear a ring sound and the lamp is turned
off.
• Refer to the note under MICROWAVE COOKING
if you want to check the cooking condition.
• Don’t touch the front screen of the door during grill
operation, because the temperature of the glass
may rise to up to 100°C. Prevent children from
touching the front screen!
• When the grill is operated for the first time after
purchasing the oven, slight smoke and smell may
occur. These will soon disappear.
POSITIONS
MAX 
600W
360W
DEFROST
90W
    
4-3
SCHEMATIC DIAGRAM
IMPORTANT SAFETY NOTE: THE SHADED AREAS ON THIS SCHEMATIC DIAGRAM INCORPORATE SPECIAL FEATURES
       
      IMPORTANT FOR PROTECTION FROM MICROWAVE RADIATION,  FIRE, 
ELECTRICAL SHOCK,  AND
                                                  HAZARDS. WHEN SERVICING IT IS ESSENTIAL THAT ONLY MANUFACTURER'S SPECIFIED PA
RTS 
                                                  BE USED FOR THE CRITICAL COMPONENTS IN THE SHADED AREAS OF THE SCHEMATIC DIAG
RAM.
NOTICE: SINCE THIS IS BASIC SCHEMATIC DIAGRAM, THE VALUES OF COMPONENTS AND
                SOME PARTIAL CONNECTIONS ARE SUBJECT TO CHANGE FOR IMPROVEMENT. 
4-4
CIRCUIT DESCRIPTION
•  As the door is closed, the contact of MONITOR
SWITCH opens. This switch creates the short circuit to
blow fuse during operation under abnormal condition.
(ie, should the contacts of primary and secondary
switch fail to open the circuit)
•  The latches are secured by latch board. The oven light
turns on while the oven is in operation.
WHEN MICROWAVE POWER LEVEL
AND COOKING TIME SET
•  The contacts of the timer switch changes to ON
position when the timer knob is rotated.
(While power control knob is set at “Full Power”)
•  The contacts of primary and secondary switch close
the circuit.
•  Input Volts AC. is applied to the high voltage
transformer through power control switch as shown by
the solid line.
•  Turntable rotates.
•  The fan motor rotates and cools the magnetron by
blowing the air (coming from the intake holes on the
baseplate) over the magnetron.
•  The air is also directed into the oven to exhaust the
vapor in the oven through the upper plate.
•  Timer starts rotating.
•  3.2 volts AC is generated from the filament winding of
the high voltage transformer. This 3.2 volts is applied
to the magnetron to heat the magnetron filament
through two noise preventing choke coils.
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
diode and charging of the high voltage capacitor.
The negative DC voltage is then applied to the filament
of the magnetron.
WHEN THE DOOR IS OPENED DURING
COOKING
•  Both primary switch and secondary switch open to cut
off the primary winding voltage to the high voltage
transformer to stop microwave oscillation.
•  Timer, turntable and fan motor stop.
•  As the door is opened, if the contact of primary 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.
WHEN THE GRILL COOKING FUNCTION
SELECTED
•  The contacts of the timer switch change to ON
position.
•  The contacts of the grill select switch close the circuit.
•  Input volts AC is applied to the grill heater through
thermostat-grill as shown by the solid line.
•  The fan motor and turntable rotates.
FUSE
PRIMARY
SWITCH
SECONDARY
SWITCH
MONITOR
SWITCH
L
N
H.V.T
RELAY
TIMER
SWITCH
POWER
CONTROL
SWITCH
FUSE
PRIMARY
SWITCH
SECONDARY
SWITCH
L
N
H.V.T
RELAY
TIMER
SWITCH
POWER
CONTROL
SWITCH
MONITOR
SWITCH
FUSE
PRIMARY
SWITCH
TIMER
SWITCH
GRILL
SELECT
SWITCH
L
N
THERMOSTAT
GRILL
GRILL 
HEATER
L
G -Y
N
E
DOOR PARTS
LATCH BOARD PARTS
CONTROL PANEL PARTS
INTERIOR PARTS
BASE PLATE PARTS
OVEN CAVITY PARTS
6-1
EXPLODED VIEW
INTRODUCTION
Page of 32
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LG MB390A Service Manual ▷ Download

  • DOWNLOAD LG MB390A Service Manual ↓ Size: 794.87 KB | Pages: 32 in PDF or view online for FREE
  • Here you can View online or download the Service Manual for the LG MB390A in PDF for free, which will help you to disassemble, recover, fix and repair LG MB390A Microwave Oven. Information contained in LG MB390A Service Manual (repair manual) includes:
  • Disassembly, troubleshooting, maintenance, adjustment, installation and setup instructions.
  • Schematics, Circuit, Wiring and Block diagrams.
  • Printed wiring boards (PWB) and printed circuit boards (PCB).
  • Exploded View and Parts List.