Panasonic NN-A720MB, Manual

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Grill, Convection And Microwave Duty Cycles
8. Cautions to Be Observed When Troubleshooting
Unlike many other appliances, the microwave oven is a high voltage, high current is device.
Though it is free from danger in ordinary use, extreme care should be taken during repair.
Caution
Servicemen should remove their watches whenever working close
to or replacing the magnetron.
8.1. Check the grounding
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
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