Cautions To Be Observed When Troubleshooting - Panasonic NN-CT867MBPQ Service Manual

9 Cautions to Be Observed When Troubleshooting

Unlike many other appliances, the microwave oven is a high
voltage, high current device. Although 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.
9.1. 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.
9.2. 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 con-
nected. 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.
NN-CT867MBPQ NN-CT857WBPQ
HV Inverter warning
WARNING FOR INVERTER POWER SUPPLY (U) GROUND-
ING
Check the high voltage inverter power supply circuit ground-
ing. 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.
17
Figure 1