Cautions When Troubleshooting - Panasonic NN-A574SBBPQ Service Manual

8 Cautions to be Observed when Troubleshooting
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.
8.1 Check the grounding
Do not operate the microwave oven on a two wire
extension cord. The microwave oven is designed to be
used only when grounded. It is imperative that the
appliance is properly grounded before beginning repair
work.
8.2 Inverter Warnings
DANGER, HIGH VOLTAGE AND HIGH TEMPERATURES
ON THE INVERTER POWER SUPPLY
HEAT SINK
RECTIFIER BRIDGE
CHOKE COIL
SAND BAR RESISTOR
CURRENT TRANSFORMER
PRESET VOLUME
(DO NOT ADJUST)
CONTROL BOARD
WITH CUSTOM IC
PHOTOCOUPLER
figure 3 HV Inverter warning
WARNING
INVERTER POWER SUPPLY GROUNDING
Check the high voltage inverter power supply circuit
grounding. The high voltage inverter circuit board
must be connected to the microwave oven chassis. If
the inverter board is not grounded it exposes very high
voltages and causes extreme DANGER! Ensure that the
inverter circuit is properly grounded via the inverter
earth bracket.
DANGER HIGH VOLTAGE AND
TEMPERATURE (HOT/LIVE) HEAT SINK
HIGH VOLTAGE TRANSFORMER
CN 701
This high voltage inverter power supply supplies very
high voltage and current to the magnetron. Though it
is free from danger in ordinary use, extreme care
should be taken during repair. This circuit looks like a
TV flyback transformer, however, the currents and volt-
ages in this circuit are very high, this means this circuit
is extremely dangerous.
The aluminium heat sink is also energized with high
voltage, never touch this heat sink when the micro-
wave oven is plugged into the mains outlet. The collec-
tor of the power device (IGBT) is directly connected to
the aluminium heat sink.
The aluminium heat sink becomes very hot when the
inverter circuit operates. Never touch this heat sink
during operation and allow time for it to cool down
before servicing the microwave oven.
CN 703
HIGH VOLTAGE REMAINS IN
CAPACITORS
9
FILM CAPACITORS
HIGH VOLTAGE
DIODES
HIGH VOLTAGE
CAPACITORS