Panasonic NN-A872SBBPQ Service Manual page 22

Do not operate on a two wire extension cord. The microwave oven is designed to be used when
grounded. It is imperative, therefore, to ensure the appliance is properly grounded before
beginning repair work.
8.2. Inverter Warnings
DANGER, HIGH VOLTAGE AND HIGH TEMPERATURE (HOT/LINE) OF THE INVERTER POWER
SUPPLY (U)
This high voltage inverter power supply 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 is therefore, dangerous due to this
high current and high voltage.
The aluminium heat sink is also energized with high voltage (HOT),
so do not touch when the AC input terminal is connected. The
power devices (Collector) is directly connected to the aluminium
heat sink.
The aluminium 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.
This 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 very high voltages and cause extreme DANGER! Be
sure that the inverter circuit is properly grounded via the inverter
earth bracket.
Figure 1
HV Inverter warning
Figure 2
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