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CAUTIONS TO BE OBSERVED WHEN TROUBLESHOOTING
Unlike many other appliances, the microwave oven is high-voltage, high
current equipment. Though it is free from danger in ordinary use, extreme
care should be taken during repair.
1. Check the grounding
Do not operate on a 2-wire extension cord. The microwave oven is
designed to be used when grounded. It is inoperative, therefore, to
make sure it is grounded properly before beginning repair work.
2. Inverter Warnings
CAUTION
Servicemen should remove their watches whenever
working close to or replacing the magnetron.
DANGER OF HIGH VOLTAGE AND HIGH
TEMPERATURE (HOT/LIVE) OF THE INVERTER
POWER SUPPLY (U)
This High Voltage Inverter Power Supply circuit supplies
very high voltage and very high current for the magnetron
tube. Though it is free from danger in ordinary use, extreme
care should be taken during repair. As you can see, it looks
like a TV flyback transformer, however the current is
extremely large and so danger exists because of its high
current and high voltages.
The aluminum heat sink is also energized with high voltage
(HOT), so do not touch when AC input terminal is connected
to the power line because one of the IGBT switching power
devices (Collector) is directly connected to the Aluminum
heat sink.
The Aluminum heat sink may be HOT from heat energy;
therefore, extreme care should be taken during servicing
and replacing.
WARNING OF INVERTER POWER SUPPLY (U)
GROUNDING
Check the High Voltage Inverter Power Supply circuit grounding.
This High Voltage Inverter Power Supply circuit board must have
a proper chassis ground by the grounding bracket to the chassis
ground; otherwise, this H.V. Inverter circuit board will expose
very high voltage and cause extreme DANGER! Be sure to have
proper grounding by the grounding plate and screws.
WARNING OF DISCHARGING HIGH VOLTAGE
CAPACITORS
Warning about the electric charge in the high voltage capacitors.
For about 30 seconds after the oven is turned off, an electric charge
remains in the high voltage capacitors in the inverter power supply
circuit board.
When replacing or checking parts, remove the power plug from
the outlet and short the Inverter output terminal of the magnetron
filament terminals to the chassis ground with an insulated handle
screwdriver to discharge. Please make sure to touch chassis
ground side first then short to the output terminals.
WARNING
There is high-voltage present, with high-current capabilities in the
circuits of the primary, and secondary windings, choke coil and
heat sink of the Inverter. It is extremely dangerous to work on or
near these circuits with oven energized.
DO NOT measure the voltage in the high voltage circuit including
filament voltage of magnetron.
WARNING
Never touch any circuit wiring with your hand nor with an
insulated tool during operation.
3. When parts must be replaced, remove the power
plug from the outlet.
4.When the 18 Amp fuse is blown due to the operation
of short switch:
(A) This is mandatory. Refer to “Measurements and Adjustments”
for these switches.
(B) When replacing the fuse, confirm that it has the appropriate
rating for these models.
(C) When replacing faulty switches, be sure mounting tabs are
not bent, broken or otherwise deficient in their ability to hold
the switches.
5.Avoid inserting nails, wire, etc. through any holes in
the unit during operation.
Never insert a wire, nail or any other metal object through the
lamp holes on the cavity or any other holes or gaps, because
such objects may work as an antenna and cause microwave
leakage.
WARNING
When the 18 Amp. fuse if blown due to the operation of
short switch, you must replace Primary latch switch and
short switch. Also replace power relay B (RY1) when the
continuity check reads shorted contacts (1-2).
MAGNETRON
FILAMENT TERMINAL
INSULATED HANDLE
SCREWDRIVER
Touch chassis side first then short to the terminal of the magnetron
filament terminal.
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NEW H.V.