Output Power - Panasonic NE-7920 Service Manual

MAGNETRON
' VARIABLE
HIGH-VOLTAGE | POWER
CAPACITOR SWITCH
A.C 2800V
TRANSFORMER
Fig. 10
(H) The coil of variable power switch is energized
intermittently by the digital programmer circuit,
when the oven is set at any power selection except
for High power position. The digital programmer
circuit controls the ON-OFF time of the variable
power switch contacts in order to vary the output
power of the microwave oven from ''Warm" to
"High'' power. One complete ON and OFF cycle of
the variable power switch is 22 seconds.
The relation between indications on the control
panel and the output of the microwave oven is as
shown in fig.11.
OUTPUT POWER ON, OFF TIME ON
INDICATION AGAINST VARIABLE
HIGH POWER POWER SWITCH
22/22 (100%) |S Fn
01S}.
20/22 (91%) aon fol on ote
Me
fe]
Warm 2/22 (10%) ON es OFF °
Warm
in Auto 1/22 (4.5%)
Cooking
d fe]
OF
OFF
Fig. 11
A13
4. When the door is opened during cooking.
(A) Latch switch A (primary) and latch switch B
(secondary) open to cut off the primary voltage
to the high voltage transformer to stop microwave
oscillation.
(B) Power indicator light (NE-7920 and NE-7920C)
or stage indicator light (NE-8020) stops blinking
but stays it.
(C) Power relay stops functioning.
(D) Oven tight remains on.
(E) Fan motor and turntable stop rotating.
(F) As soon as the door handle button is pressed, the
short switch contacts close and create the short
circuit.
(G) If the contacts of latch switch A and the contacts of
latch switch B both malfunction, the 15 A fuse
blows open due to the large current surge caused by
the short switch activation, and this in turn stops
magnetron oscillation.
HIGH-VOLTAGE
TRANSFORMER
15A LATCH POWER LATCH
FUSE SWITCH A RELAY SWITCH B
Fig. 12
5. When Reset/Stop pad is tapped once during cooking.
(A) The digital programmer circuit cuts the voltage
supplied to the power relay coil causing the mag-
netron to stop oscillation.
(B) Power indicator light (NE-7920 and NE-7920C) or
Stage indicator light (NE-8020) stops blinking and
stays on.
(C) Oven light turns off,
(D) Fan motor and turntable stop rotating.
NOTE:At this moment, the oven is in "hold'' condition
and when the start pad is touched again, the oven
starts to operate as originally programmed.
6. When Reset/Stop pad is tapped twice during cooking.
(A) The digital programmer circuit cancels al! instruc-
tions given.
(B) Power relay stops functioning to stop magnetron
oscillation.
(C) Any indications displayed during cooking turn off
and display shows TOD.
(D) Oven light turns off.
{E) Fan motor and turntable stop rotating.