Measurement Of Microwave Power Output; Disassembly And Adjustment - LG MC-3089NBC Service Manual

MEASUREMENT OF MICROWAVE POWER OUTPUT

• 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 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
190 mm.
• The oven and the empty vessel are at ambient
temperature prior to the start of the test.
• The initial temperature (±1)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 shelf 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.

DISASSEMBLY AND ADJUSTMENT

A. OUTER CASE REMOVAL
1) Disconnect the power supply cord from the outlet.
2) Remove the screws from the rear and along side edges of
the case. The outer case must be moved backward to be
lifted off.
B. POWER SUPPLY CORD REMOVAL
1) Remove the outer case.
2) Disconnect two terminals, and remove one screw of the
earth terminal.
CAUTION: DISCHARGE THE HIGH VOLTAGE
CAPACITOR BEFORE SERVICING (refer to page 2-1)
LGE Internal Use Only
• The microwave power output P in watts is calculated
from the following formula :
4187 x
P =
• T : Temperature after heating
2
• T : Temperature of bowl
0
• M : Weight of bowl
is measured while the microwave generator is
operating at full power. Magnetron filament heat-up
time is not included.
• 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.
WATER LOAD
C. CONTROLLER ASSEMBLY REMOVAL
1) Disconnect the leadwire from the PCB SUB ASS'Y.
2) Remove the screws for the earth and securing the control
panel.
3) Lift control panel ASS'Y from the oven by the tab
unhooked.
D. PCB ASSEMBLY REMOVAL
1) Remove the control panel assembly from the cavity.
(Refer to control panel assembly removal on previous page.)
2) Remove screws which hold the PCB SUB ASS'Y to the
control panel.
3) Take off the PCB SUB ASS'Y from the control panel.
5-3 Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
(∆T) + 0.55 X (T -T )X M
2 0
T
TURNTABLE