Inverter NN-T551CB, Service Manual

Page: 16 / 63

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.
7.2. 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 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.
Figure 1
HV Inverter warning
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