Panasonic NN-V629MB, Service Manual

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11
5. 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.
5.1 Check the grounding
Do not operate on a 2-wire extension cord. The microwave oven
is designed to be used when grounded. It is imperative,
therefore, to make sure it is grounded properly before beginning
repair work.
5.2 Inverter Warnings
CAUTION
Servicemen should remove their watches whenever working
close to or replacing the magnetron.
DANGER OF HIGH VOLTAGE AND HIGH TEMPERATURE
(HOT/LINE) OF THE INVERTER POWER SUPPLY (U)
This High Voltage Inverter Power Supply circuit handles 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 by its high current and high
voltages.
The aluminium heat sink is also energized with high voltage
(HOT), so do not touch when AC input terminal is connected
to the power devices (Collector) is directly connected to the
Aluminium heat sink.
The Aluminium heat sink may be HOT by heat energy; there-
fore, 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.
NEW H.V.
HIGH VOLTAGE REMAINS IN
HIGH VOLTAGE CAPACITORS
DANGER OF HIGH VOLTAGE AND HIGH
TEMPERATURE (HOT/LIVE) OF HEAT SINK
HEAT SINK
CHOKE COIL
SAND BAR
RESISTOR
CUSTOM I.C.
CN 701
CURRENT
TRANSFORMER
CN 703
SECONDARY
WINDINGS
DIODE
HIGH VOLTAGE
PRIMARY
WINDINGS
HIGH VOLTAGE
TRANSFORMER
FILM
CAPACITORS
PHOTO
COUPLER
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 fila-
ment voltage of magnetron.
WARNING
Never touch any circuit wiring with your hand nor with an
insulated tool during operation.
H.V. INVERTER(U)
BE SURE TO HAVE PROPER
GROUNDING PLATE
GROUNDING
MAGNETRON FILAMENT
INSULATED HANDLE
Touch chassis side first then short to the
term inal of the m agnetron filam ent term inal
SCREWDRIVER
TERMINAL