Panasonic NN-P295, Service Manual

Page: 59 / 92

DANGER OF HIGH VOLTAGE AND HIGH /
TEMPERATURE (HOT/LIVE) OF THE INVERTER /
POWER SUPPLY (U)
This High Voltage Inverter Power Supply circuit
supplies 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 so danger exists because of
its high current and high voltages.
The aluminum heat sink is also energized with
high voltage (HOT), so do not touch when AC
input terminal is connected to the power line
because one of the IGBT switching power devices
(Collector) is directly connected to the Aluminum
heat sink.
The Aluminum heat sink may be HOT from heat
energy; therefore, extreme care should be taken
during servicing and replacing.
WARNING OF 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 by the grounding bracket to the
chassis ground; otherwise, this H.V. Inverter
circuit board will expose very high voltage and
cause extreme DANGER! Be sure to have proper
grounding by the grounding plate and screws.
WARNING OF DISCHARGING HIGH VOLTAGE
CAPACITORS
Warning about the electric charge in the high
voltage capacitors. For about 30 seconds after the
oven is turned off, an electric charge remains in
the high voltage capacitors in the inverter power
supply circuit board.
When replacing or checking parts, remove the
power plug from the outlet and short the Inverter
output terminal of the magnetron filament
terminals to the chassis ground with an insulated
handle screwdriver to discharge. Please make sure
to touch chassis ground side first then short to the
output terminals.
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