Panasonic NN-S554WF Service Manual page 8

2.1. Check the grounding
Do not operate on a two wire extension cord. The microwave oven is designed to be grounded
when used. It is imperative, therefore, to ensure the appliance is properly grounded before
beginning repair work.
2.2. Inverter warnings
DANGER, HIGH VOLTAGE AND HIGH TEMPERATURE (HOT/LINE) OF THE INVERTER POWER
SUPPLY (U)
The high voltage inverter power supply handles very high voltage
and current for the magnetron tube. Though it is free from danger
in ordinary use, extreme care should be taken during repair.
The aluminum heat sink is also energized with high voltage (HOT),
do not touch when the AC input terminals are energized. The power
device Collector is directly connected to the aluminum heat sink.
The aluminum heat sink may be HOT due to heat energy, therefore,
extreme care should be taken during servicing.
WARNING FOR INVERTER POWER SUPPLY (U) GROUNDING
Check the high voltage inverter power supply circuit grounding.
The high voltage inverter power supply circuit board must have a
proper chassis ground. The inverter grounding bracket must be
connected to the chassis. If the inverter board is not grounded it
will expose the user to very high voltages and cause extreme
DANGER! Be sure that the inverter circuit is properly grounded via
the inverter earth bracket.
H.V. Inverter warning
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