Panasonic NN-DF383BZPE Service Manual ▷ View online
1 SCHEMATIC DIAGRAM
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NN-DF383B
2.1. Variable power cooking
control
High Voltage Inverter Power Supply (U) controls output power
by the signal from Digital Programmer Circuit (DPC). Power
relay always stay on, but PWM (Pulse Width Modulation) signal
controls microwave output power.
NOTE:
by the signal from Digital Programmer Circuit (DPC). Power
relay always stay on, but PWM (Pulse Width Modulation) signal
controls microwave output power.
NOTE:
The ON/OFF time ratio does not correspond with the
percentage of microwave power since approximately 2
seconds are required for heating of magnetron
filament.
percentage of microwave power since approximately 2
seconds are required for heating of magnetron
filament.
Variable Power Cooking
POWER SETTING
OUTPUT
POWER(%)
APPROX.
MANUAL MICROWAVE
DUTY
ON(SEC)
OFF(SEC)
HIGH
100%
22
0
MEDIUM-HIGH
80%
22
0
MEDIUM
60%
22
0
MEDIUM-LOW
40%
22
0
DEFROST
30%
18
4
LOW
20%
13
9
2.2. Inverter power supply circuit
The Inverter Power Supply circuit powered from the line
voltage, 220V 50Hz AC input supplies 4,000V DC to the
magnetron tube, and functions in place of the H.V. transformer,
the H.V. capacitor and H.V. diode.
1. The AC input voltage 220V 50Hz is rectified to DC voltage
voltage, 220V 50Hz AC input supplies 4,000V DC to the
magnetron tube, and functions in place of the H.V. transformer,
the H.V. capacitor and H.V. diode.
1. The AC input voltage 220V 50Hz is rectified to DC voltage
immediately.
2. DC voltage will be supplied to the switching devices called
IGBT. These devices are switched ON-OFF by the 20 to 40
kHz PWM (pulse width modulation) signal from the
microcomputer in the DPC.
kHz PWM (pulse width modulation) signal from the
microcomputer in the DPC.
3. This drives the High voltage transformer to increase voltage
up to 2,000V AC.
4. Then the half-wave doubler voltage rectifier circuit,
consisting of the H.V. diodes and capacitors, generates the
necessary 4,000V DC needed for the magnetron.
necessary 4,000V DC needed for the magnetron.
5. Output power of the magnetron tube is always monitored by
the signal output from the current transformer built into the
inverter circuit.
inverter circuit.
6. This signal is fed back to the microcomputer in the DPC to
determine operating conditions and output necessary to
control PWM signal to the Inverter Power Supply for control
of the output power.
control PWM signal to the Inverter Power Supply for control
of the output power.
2.3. Turbo defrost, Auto cook
When the Auto Control feature is selected and the Start pad is
tapped:
1. The digital programer circuit determines the power level and
tapped:
1. The digital programer circuit determines the power level and
cooking time to complete cooking and indicates the
operating state in the display window.
operating state in the display window.
2. When cooking time in the display window has elapsed, the
oven turns off automatically by a control signal from the
digital programmer circuit.
digital programmer circuit.
Turbo Defrost
PROGRAM
WEIGHT SELECTED
COOKING TIME
VEGETABLES
200g
2 min 10 sec.
2.4. Sensor cooking
Auto sensor cooking without setting a power level or selecting
a time. All that is necessary is to select an Auto Sensor
Program before starting to cook.
Understanding Auto Sensor Cooking
a time. All that is necessary is to select an Auto Sensor
Program before starting to cook.
Understanding Auto Sensor Cooking
As the food cooks, a certain amount of steam is produced.
If the food is covered, this steam builds up and eventually
escapes from the container. In Auto Sensor Cooking, a
carefully designed instrument, called the steam sensor
element, senses this escape of steam. Then, based upon
the Auto Sensor Program selected, the unit will
automatically determine the correct power level and the
proper length of time it will take to cook the food.
If the food is covered, this steam builds up and eventually
escapes from the container. In Auto Sensor Cooking, a
carefully designed instrument, called the steam sensor
element, senses this escape of steam. Then, based upon
the Auto Sensor Program selected, the unit will
automatically determine the correct power level and the
proper length of time it will take to cook the food.
NOTE:
Auto Sensor Cooking is successful with the foods and
recipes found in the Auto Sensor Cooking Guide.
Because of the vast differences in food composition,
items not mentioned in the Cooking Guide should be
prepared in the microwave oven using power select
and time features. Please consult Variable Power
Microwave Cookbook for procedures.
recipes found in the Auto Sensor Cooking Guide.
Because of the vast differences in food composition,
items not mentioned in the Cooking Guide should be
prepared in the microwave oven using power select
and time features. Please consult Variable Power
Microwave Cookbook for procedures.
2 DESCRIPTION OF OPERATING SEQUENCE
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Explanation of the Auto Sensor Cooking process
1. During the first 10 second period there is no microwave
activity. When calculating the T2 time by using the
formula below make sure this 10 seconds is subtracted
from the T1 time. In other words, T1 time starts at the
end of the 10 second period.
formula below make sure this 10 seconds is subtracted
from the T1 time. In other words, T1 time starts at the
end of the 10 second period.
2. T1 time The total amount of time it takes the microwave
oven to switch to T2 time after the 10second period.
3. T2 time When the steam escapes from the cooking
container placed in the oven, the steam sensor detects
it and the microprocessor calculates the balance of
cooking time. This T2 time is then shown in the display
and begins counting down.
Balance of cooking time (T2 time)
The balance of cooking time which is called T2 time,
can be calculated by the following formula.
T2 time (in sec.) = T1 time X K factor
it and the microprocessor calculates the balance of
cooking time. This T2 time is then shown in the display
and begins counting down.
Balance of cooking time (T2 time)
The balance of cooking time which is called T2 time,
can be calculated by the following formula.
T2 time (in sec.) = T1 time X K factor
NOTE:
Remember, the T1 time starts after the 10 second
period. The coefficient K is programmed into the
microprocessor memory and they are listed in the
following tables along with the P1 and P2 powers.
period. The coefficient K is programmed into the
microprocessor memory and they are listed in the
following tables along with the P1 and P2 powers.
NOTE:
When "More" or "Less" pad is selected, the K factor
varies resulting in T2 time to be increased or decreased.
varies resulting in T2 time to be increased or decreased.
Example of calculating the T2 time
Example 1: If the T1 time is measured to be 2 minutes and
40 seconds after the 10 second period.
T2 = T1 × K ± 10 sec.
= 2 min. and 40 sec. × 0.1 ± 10 sec.
= 16 sec. ± 10 sec.
= ± 10 sec.
40 seconds after the 10 second period.
T2 = T1 × K ± 10 sec.
= 2 min. and 40 sec. × 0.1 ± 10 sec.
= 16 sec. ± 10 sec.
= ± 10 sec.
CATEGORY
P1
POWER
P2
POWER
K FACTOR
STANDARD
SENSOR
REHEAT
MEDIUM
POWER
LOW
POWER
0
2.5. Steam sensor and digital
programmer circuit
In order to determine if the steam sensor function of the digital
programmer circuit is working, do the following test.
1. Place a water load (100 cc) in the oven.
2. Tap Sensor Reheat pad.
3. Tap Start pad.
4. Steam Sensor detects steam about 1.5 to 2 minutes after
programmer circuit is working, do the following test.
1. Place a water load (100 cc) in the oven.
2. Tap Sensor Reheat pad.
3. Tap Start pad.
4. Steam Sensor detects steam about 1.5 to 2 minutes after
the Start pad is tapped.
5. T1 time cooking automatically switches to remaining time
for cooking (T2).
6. The remaining cooking time (T2) appears in display
window. If the following cooking time appears, Steam
Sensor function is normal.
Sensor function is normal.
T1 TIME
T2 TIME (Remainingcooking time)
50 Sec. ~ 2 Min.
0 Sec. ~ 24 Sec.
2.6. Grill cooking control
Grill cooking is accomplished by upper heaters only. One grill
cooking cycle is 33 seconds.
1. During grill cooking, the digital programmer circuit controls
cooking cycle is 33 seconds.
1. During grill cooking, the digital programmer circuit controls
power relay RY4´s ON-OFF time. In all three grill cooking
categories, power relay RY1 always stay ON, but RY4´s
ON-OFF time are shown in Figure.
categories, power relay RY1 always stay ON, but RY4´s
ON-OFF time are shown in Figure.
GRILL
CATEGORY
GRILL (RY4)
MICROWAVE (DUTY)
ON (sec.)
OFF (sec.)
ON (sec.)
OFF (sec.)
1
33
0
2
24
9
0
33
3
18
15
2.7. Combination Cooking
Combination cooking is accomplished by microwave and grill
cooking (upper heaters) being done synchronously during one
combination cooking cycle. One combination cooking cycle is
33 seconds.
1. During combination cooking, the digital programmer circuit
cooking (upper heaters) being done synchronously during one
combination cooking cycle. One combination cooking cycle is
33 seconds.
1. During combination cooking, the digital programmer circuit
controls power relay RY4 & RY1´s duty ON-OFF time. In all
three combination cooking categories, power relay RY4 &
RY1’s duty ON-OFF time are as shown in Figure.
three combination cooking categories, power relay RY4 &
RY1’s duty ON-OFF time are as shown in Figure.
COMBINATION
CATEGORY
GRILL(RY4)
MICROWAVE(DUTY)
ON(sec.)
OFF(sec.)
ON(sec.)
OFF(sec.)
1
33
0
33
0
2
24
9
33
0
3
16
17
23
10
2.8. Oven cooking control
The digital programmer circuit controls the ON-OFF time of the
heater in order to control oven cavity temperature.
1. After selecting desired oven cavity temperature of oven (the
heater in order to control oven cavity temperature.
1. After selecting desired oven cavity temperature of oven (the
range of selected oven temp is 100°C-220°C) and pressing
[Start] pad, a high level signal comes out of the micro
computer and applies to power relays, RY4 & RY6.
[Start] pad, a high level signal comes out of the micro
computer and applies to power relays, RY4 & RY6.
2. When RY4 & RY6 are switched to ON, power source
voltage is applied to the upper heater & lower heater, and
the heaters turn on.
the heaters turn on.
3. The digital programmer circuit senses the oven cavity
temperature through oven temp sensor (thermistor). When
the oven temperature reaches the set temperature, DPC
stops supplying high level signal to the power relays, and
the heaters turn off.
the oven temperature reaches the set temperature, DPC
stops supplying high level signal to the power relays, and
the heaters turn off.
4. After the upper heater and lower heater turn off, the oven
temperature will continue increasing for a while and then
decrease as shown in Figure.
When the oven temperature drops below the set
temperature, the digital programmer circuit senses the
signal and starts supplying a high level signal to RY4 & RY6
again.
decrease as shown in Figure.
When the oven temperature drops below the set
temperature, the digital programmer circuit senses the
signal and starts supplying a high level signal to RY4 & RY6
again.
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Unlike many other appliances, the microwave oven is a high
voltage, high current device. It is free from danger in ordinary
use, though extreme care should be taken during repair.
voltage, high current device. It is free from danger in ordinary
use, though extreme care should be taken during repair.
CAUTION
Servicemen should remove their watches & rings whenever
working close to or replacing the magnetron.
working close to or replacing the magnetron.
3.1. Check the grounding
Do not operate on a two wire extension cord. The microwave
oven is designed to be grounded when used. It is imperative,
therefore, to ensure the appliance is properly grounded before
beginning repair work.
oven is designed to be grounded when used. It is imperative,
therefore, to ensure the appliance is properly grounded before
beginning repair work.
3.2. Inverter warnings
WARNING HIGH VOLTAGE AND HIGHTEMPERATURE
(HOT/LIVE) OF THE INVERTERPOWER SUPPLY (U)
The High Voltage Inverter Power Supply generates 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.
The aluminum heat sink is also energized with high voltage
(HOT), do not touch when the AC input terminals are
energized. The power device Collector is directly connected
to the aluminum heat sink.
The aluminum heat sink may be HOT due to heat energy,
therefore, extreme care should be taken during servicing.
high voltage and current for the magnetron tube. Though it
is free from danger in ordinary use, extreme care should be
taken during repair.
The aluminum heat sink is also energized with high voltage
(HOT), do not touch when the AC input terminals are
energized. The power device Collector is directly connected
to the aluminum heat sink.
The aluminum heat sink may be HOT due to heat energy,
therefore, extreme care should be taken during servicing.
H.V. 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 plate must be connected to the chassis. If the
inverter board is not grounded it will expose the user to very
high voltages and cause extreme DANGER! Be sure that
the inverter circuit is properly grounded via the inverter
grounding plate.
grounding. The high voltage inverter power supply circuit
board must have a proper chassis ground. The inverter
grounding plate must be connected to the chassis. If the
inverter board is not grounded it will expose the user to very
high voltages and cause extreme DANGER! Be sure that
the inverter circuit is properly grounded via the inverter
grounding plate.
WARNING
DISCHARGE
THE
HIGH
VOLATGE
CAPACITORS
For about 30 seconds after the oven is turned off, an
electric charge remains in the high voltage capacitors of 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 be sure
to contact the chassis ground side first and then short to the
output terminal.
electric charge remains in the high voltage capacitors of 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 be sure
to contact the chassis ground side first and then short to the
output terminal.
3 CAUTIONS TO BE OBSERVED WHEN
TROUBLESHOOTING
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