Panasonic Inverter NN-CT776SBPQ Service Manual page 8

figure 4Grounding of the inverter circuit board
WARNING! DISCHARGE THE HIGH VOLTAGE CAPACI-
TORS
For about 30 seconds after the oven is turned off, an
electric charge remains in the high voltage capacitors
on the inverter circuit board.
figure 5Discharging the high voltage capacitors
1. Before replacing or testing parts discharge these
high voltage capacitors by shorting the inverter
ouput terminal to the microwave oven chassis
2. Remove the power plug from the mains outlet
3. Ensure that the high voltage lead is connected to
the inverter output terminals and the magnetron
input terminals.
4. Short the magnetron input terminal to the micro-
wave oven chassis using an insulated handle screw-
driver.
5. Always touch the microwave oven chassis and then
the magnetron terminal.
WARNING
There is high voltage with high current capabilities in
the primary, secondary windings, choke coil and heat
sink on the inverter circuit. When power is connected
to the microwave oven, it is extremely dangerous to
H.V.INVERTER(U)
GROUNDING PLATE
CHECK
GROUNDING
work on or near these inverter circuit components. DO
NOT measure the voltage in the high voltage circuit
including the filament voltage of the magnetron.
WARNING
Never touch any circuit wiring during operation.
8.3 Part replacement
When replacing any component in the microwave oven,
always ensure that the power cord is removed from the
wall outlet.
8.4 When the 10A fuse is blown due
to the operation of the short
switch
WARNING
Always replace both the short switch and the primary
latch switch when the 10A 250V fuse is blown due to
the operation of the short switch. It is also important to
change the power relay 1 (RY1) when the continuity
test shows shorted contacts.
1. This is mandatory. Refer to "adjustments and meas-
urements" for the location of these switches.
2. When replacing the fuse, confirm that it has the
appropriate rating for these models.
3. When replacing faulty switches, be sure the mount-
ing tabs are not bent, broken or deficient in their
ability to hold the switches.
8.5 Oven cavity aperatures
Never insert a wire or any other metal object through
the lamp holes or other aperatures in the oven cavity,
because such objects may work as an antenna and
cause microwave leakage.
8.6 Confirm after repair
1. After repair or replacement of parts, make sure that
the screws of the oven are neither loose nor miss-
ing. Microwaves might leak if screws are not prop-
erly tightened.
2. Make sure that all electrical connections are tight
before inserting the plug into the wall outlet.
3. Check for microwave energy leakage. (Refer to pro-
cedure for measuring microwave energy leakage).
CAUTION MICROWAVE ENERGY
Microwave energy is emitted from the magnetron
attenna into the oven cavity via the wave guide. Do not
opearate the microwave oven if the door is defective,
the magnetron is not fitted correctly or the outer panel
is removed.
IMPORTANT NOTICE
When the microwave oven is operating the following
components carry a potential above 240VAC.
• Magnetron
• High voltage transformer (Located on inverter)
• High voltage diodes (Located on inverter )
• High voltage capacitors (Located on inverter )
Pay special attention in these areas.
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