NN-SN968B NN-SN968BT - Philips Parts and Accessories

ORDER NO.PHAMOS0912075C1
E1
Microwave Oven
NN-SN968B
NN-SN968BT
APH (USA)
© Panasonic Home Appliances Microwave Oven
(Shanghai) Co., Ltd. 2009.
NN-SN968B / NN-SN968BT
2
NN-SN968B / NN-SN968BT
3
NN-SN968B / NN-SN968BT
CONTENTS
Page
Page
1 SCHEMATIC DIAGRAM
5
5.4. Inverter power supply (U)
15
2 DESCRIPTION OF OPERATING SEQUENCE
6
5.5. Temperature thermistor
15
2.1. Variable power cooking control
6
2.2. Inverter power supply circuit
6
2.3. Inverter defrost
6
2.4. Sensor cooking
6
2.5. Sensor reheat
7
2.6. Steam sensor and digital programmer circuit
7
2.7. Thermistor
7
6 MEASUREMENTS AND ADJUSTMENTS
16
6.1. Adjustment of primary latch switch, secondary latch switch
and monitor interlock switch.
6.2. Measurement of microwave output
16
16
7 PROCEDURE FOR MEASURING MICROWAVE ENERGY
LEAKAGE
3 CAUTIONS TO BE OBSERVED WHEN TROUBLESHOOTING 8
17
7.1. Equipment
17
7.2. Procedure for measuring radiation leakage
17
17
3.1. Check the grounding
8
7.3. Record keeping and notification after measurement
3.2. Inverter warnings
8
7.4. At least once a year, have the radiation monitor checked
3.3. Part replacement.
9
for calibration by its manufacturer.
3.4. When the 20A fuse is blown due to the malfunction of the
8 TROUBLESHOOTING GUIDE
9
monitor interlock switch:
18
19
8.1. (Troubleshooting) Oven stops operation during cooking 19
3.5. Avoid inserting nails, wire etc. through any holes in the
8.2. (Troubleshooting) Other problems
20
9
8.3. Troubleshooting of inverter circuit (U) and magnetron
21
3.6. Verification after repair
9
8.4. Trouble related to Digital Programmer Circuit
22
3.7. Sharp edges
9
8.5. SIMPLE WAY OF H.V. INVERTER/MAGNETRON
unit during operation.
4 DISASSEMBLY AND PARTS REPLACEMENT PROCEDURE 10
4.1. Magnetron
10
4.2. Digital programmer circuit (D.P.C)
10
TROUBLESHOOTING
23
8.6. H.V.INVERTER BOARD MAIN PARTS LIST
(F606Y8X00AP)
23
8.7. How to check the semiconductors using an OHM meter 24
4.3. Low voltage transformer and/or power relays (RY1, RY2)
9 EXPLODED VIEW AND PARTS LIST
11
25
4.4. Fan motor
11
9.1. EXPLODED VIEW
25
4.5. Door assembly
11
9.2. PARTS LIST
26
4.6. Turntable motor
12
9.3. ESCUTCHEON BASE ASSEMBLY
27
4.7. Steam sensor
12
9.4. DOOR ASSEMBLY
28
4.8. Inverter power supply
13
9.5. WIRING MATERIALS
29
14
9.6. PACKING AND ACCESSORIES
30
5 COMPONENT TEST PROCEDURE
5.1. Primary, Secondary Latch Switch interlocks & Power
10 DIGITAL PROGRAMMER CIRCUIT
31
14
10.1. SCHEMATIC DIAGRAM
31
5.2. Monitor Interlock Switch
14
10.2. PARTS LIST
33
5.3. Magnetron
14
Relay RY1
4
NN-SN968B / NN-SN968BT
1 SCHEMATIC DIAGRAM
5
NN-SN968B / NN-SN968BT
2 DESCRIPTION OF OPERATING SEQUENCE
2.1.
Variable power cooking
control
2.3.
When the Auto Control feature is selected and the Start button
is tapped:
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.
1. The digital programer circuit determines the power level and
cooking time to complete cooking and indicates the
operating state in the display window. Table shows the
corresponding cooking times for respective serving by
categories.
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.
Inverter Turbo Defrost
SELECTED WEIGHT
COOKING TIME
1.0 LB
4 min.45 sec.
2. When cooking time in the display window has elapsed, the
oven turns off automatically by a control signal from the
digital programmer circuit.
Variable Power Cooking
POWER SETTING
OUTPUT
MANUAL MICROWAVE
POWER(%)
DUTY
APPROX.
ON(SEC)
OFF(SEC)
HIGH
P10
100%
22
0
P9
90%
22
0
P8
80%
22
0
MEDIUM-HIGH
P7
70%
22
0
MEDIUM
P6
60%
22
0
P5
50%
22
0
P4
40%
22
0
MEDIUM-LOW
P3
30%
22
0
P2
20%
15
7
P1
10%
8
14
DEFROST
P3
30%
22
0
2.2.
Inverter defrost
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
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.
Inverter power supply circuit
The Inverter Power Supply circuit powered from the line
voltage, 120V 60Hz 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.
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.
1. The AC input voltage 120V 60Hz 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.
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.
5. Output power of the magnetron tube is always monitored by
the signal output from the current transformer built into the
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.
6
NN-SN968B / NN-SN968BT
2.5.
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.
Auto Sensor Reheat is a quick and easy way to reheat
refrigerated and room temperature foods.
Simply press the reheat button. There is no need to select
power level and cooking time.
NOTE:
2. T1 time The total amount of time it takes the microwave
oven to switch to T2 time after the 10second period.
The Auto Sensor Reheat process is same as Auto Sensor
Cooking process.
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.
Category
Sensor Reheat
2.6.
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
Steam sensor and digital
programmer circuit
3. Tap Start button.
4. Steam Sensor detects steam about 1.5 to 4 minutes after
the Start button is tapped.
5. T1 time cooking automatically switches to remaining time
for cooking (T2).
When "More" or "Less" button is selected, the K factor
varies resulting in T2 time to be increased or decreased.
6. The remaining cooking time (T2) appears in display
window. If the following cooking time appears, Steam
Sensor function is normal.
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, and the Auto
program selected is Oatmeal:
T1 TIME
1 Min. 30 Sec. ~ 4 Min.
T2 = T1 × K
= 2 min. and 40 sec. × 0.1
2.7.
= 160sec. × 0.1
T2 TIME (Remainingcooking time)
27 Sec. ~ 1Min.12 Sec.
Thermistor
The thermistor which fixed on magnetron detects magnetron
temperature and make power down when the temperature
becomes abnormal high. A normal thermistor´s resistance
values for temperature ranges between 75-85 degree F is from
37kΩ to 57kΩ.
= 16 sec.
Omelet
K Factor
Standard
0.2
2. Tap Sensor Reheat button.
NOTE:
P2
Power
MEDIUM
P2
Power
MEDIUM
1. Place a water load (150 cc) in the oven.
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.
P1
Power
MEDIUM
P1
Power
HIGH
In order to determine if the steam sensor function of the digital
programmer circuit is working, do the following test.
NOTE:
Category
Sensor reheat
K Factor
Standard
0.6
7
NN-SN968B / NN-SN968BT
3 CAUTIONS TO BE OBSERVED WHEN
TROUBLESHOOTING
Unlike many other appliances, the microwave oven is a high
voltage, high current device. Though it is free from danger in
ordinary use, extreme care should be taken during repair.
CAUTION
Servicemen should remove their watches and rings
whenever 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.
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.
Grounding of the inverter circuit board
WARNING
CAPACITORS
DISCHARGE
THE
HIGH
VOLATGE
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.
The aluminum heat sink may be HOT due to heat energy,
therefore, extreme care should be taken during servicing.
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.
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.
8
NN-SN968B / NN-SN968BT
3.6.
Discharging the high voltage capacitors
WARNING
1. After repair or replacement of parts, make sure that the
screws of the oven, etc. are neither loosen or missing.
Microwave energy might leak if screws are not properly
tightened.
There is high voltage present with high current capabilities
in the circuits of the primary and secondary windings, choke
coil and heat sink of the inverter. It is extremely dangerous
to work on or near these circuits with the oven energized.
DO NOT measure the voltage in the high voltage circuit
including the filament voltage of the magnetron.
2. Make sure that all electrical connections are tight before
inserting the plug into the wall outlet.
3. Check for microwave energy leakage. (Refer to procedure
for measuring microwave energy leakage).
WARNING
Never touch any circuit wiring with your hand or with an
insulated tool during operation.
3.3.
CAUTION OF MICROWAVE RADIATION LEAKAGE
USE CAUTION NOT TO BECOME EXPOSED TO
RADIATION FROM THE MICROWAVE MAGNETRON OR
OTHER PARTS CONDUCTING MICROWAVE ENERGY.
Part replacement.
When troubleshooting any part or component is to be replaced,
always ensure that the power cord is unplugged from the wall
outlet.
3.4.
IMPORTANT NOTICE
1. The following components have potentials above 2000V
while the appliance is operated.
When the 20A fuse is blown
due to the malfunction of the
monitor interlock switch:
• Magnetron
• High voltage transformer (Located on inverter (U))
• High voltage diodes (Located on inverter (U))
• High voltage capacitors (Located on inverter (U))
WARNING
Pay special attention to these areas.
When the 20A 120V fuse is blown due to the malfunction of
the monitor interlock switch, replace all of the components
(primary latch switch, monitor interlock switch and power
relay RY1).
2. When the appliance is operated with the door hinges or
magnetron installed incorrectly, the microwave leakage
can exceed more than 5mW/cm 2. After repair or
exchange, it is very important to check if the magnetron
and the door hinges are correctly installed.
1. This is mandatory. Refer to “measurements and
adjustments” for the location of these switches.
3.7.
2. When replacing the fuse, confirm that it has the
appropriate rating for these models.
Sharp edges
CAUTION
3. When replacing faulty switches, be sure the mounting
tabs are not bent, broken or deficient in their ability to
hold the switches.
3.5.
Verification after repair
Please use caution when disassembling or reassembling
internal parts. Some exposed edges may be sharp to the
touch and can cause injury if not handled with care.
Avoid inserting nails, wire etc.
through any holes in the unit
during operation.
Never insert a wire, nail or any other metal object through the
lamp holes on the cavity or any holes or gaps, because such
objects may work as an antenna and cause microwave
leakage.
9
NN-SN968B / NN-SN968BT
4 DISASSEMBLY AND PARTS REPLACEMENT
PROCEDURE
4.1.
Magnetron
4.2.
1. Discharge high voltage charge.
Digital programmer circuit
(D.P.C)
2. Remove 1 screw holding air guide A on the oven cavity.
CAUTION:
3. Remove 1 screw holding air guide B.
Be sure to ground any static electric charge built up in
your body before handling the DPC.
4. Remove 1 screw holding themistor.
1. Disconnect all connectors from D.P.C.
2. Remove 1 grounding screw.
3. Remove 1 screw holding escutcheon base and slide the
escutcheon base upward slightly.
5. Disconnect 2 high voltage lead wires from magnetron
filament terminals.
4. Remove all screws holding D.P.C. board on escutcheon
base.
6. Remove 4 screws holding the magnetron.
5. Separate D.P.C board from tabs on the escutcheon base
and remove D.P.C board.
NOTE:
After replacement of the magnetron, tighten mounting
screws properly in an x pattern, making sure there is no
gap between the waveguide and the magnetron to
prevent microwave leakage.
CAUTION
When replacing the magnetron, be sure the antenna gasket is in
place.
10
NN-SN968B / NN-SN968BT
4.3.
Low voltage transformer
and/or power relays (RY1,
RY2)
4.5.
1. Remove door C from door E by carefully pulling outward,
starting from upper right hand corner using a flat blade
screwdriver.
CAUTION:
2. Separate door E from tabs on door A and remove door A.
Be sure to ground any static electric charge built up in
your body before handling the DPC.
3. Open Door E at the opening angle of approximately
10°(Note: The door cannot be removed if the opening
angle is greater than 10°).
1. Replace D.P.C. board.
(A) Using solder wick or a desoldering tool and 30W
soldering iron carefully remove all solder from the terminal
pins of the low voltage transformer and/or power relays.
4. Remove the door E from its hinges by pushing the door E
upward and out.
5. Remove door screen B from door A.
CAUTION:
6. Remove door key and door key spring.
Do not use a soldering iron or desoldering tool of
more than 30 watts on D.P.C. contacts.
To re-install components:
1. Place the door’s lower hinge pin into the bottom hinge
hole.
(B) With all the terminal pins cleaned and separated from
D.P.C. contacts, remove the defective transformer/power
relays, Replace components making sure all terminal pins
are inserted completely resolder all terminal contacts
carefully.
4.4.
Door assembly
2. Use your left index finger to support the door’s lower
hinge pin while guiding the door’s upper hinge pin into
the top hinge hole.
3. Lower your finger to seat the door onto the hinges.
Fan motor
4. Replace other components.
NOTE:
1. Disconnect 2 lead wires from fan motor terminals.
Adjust so that the upper portion of the door will
touch firmly to the oven cavity front plate, without
pushing the door. If the door assembly is not
mounted properly, microwave power may leak from
the clearance between the door and oven.
2. Remove 2 screws at location on oven attaching orifice
assembly.
3. Remove orifice assembly from oven assembly.
4. Remove fan blade from the fan motor shaft by pulling it
straight out.
NOTE:
5. Remove 2 screws holding fan motor to orifice.
Always
perform
the
microwave
leakage
measurement test after installation and adjustment
of door assembly.
11
NN-SN968B / NN-SN968BT
4.6.
Turntable motor
4.7.
1. Remove the motor cover by breaking off at the 8 spots
indicated by arrows with a cutter or the like.
Steam sensor
1. Disconnect connector CN2 from digital programmer circuit
board.
2. Disengage catch hooks on sensor cover C from orifice.
NOTE:
After removing the motor cover, be sure that cut
portions are properly trimmed or bent to the inside
so that no sharp edges will be exposed to outside.
2. Disconnect 2 lead wires connected to the turntable motor.
3. Remove steam sensor from orifice.
3. Remove the turntable motor by removing screw.
NOTE:
When installing the steam sensor, make sure that
the direction of steam sensor is as shown in figure.
NOTE:
After reinstalling the new turntable motor and
reconnecting the 2 lead wires, reinstall the motor
cover by rotating it around 180, tucking the 2 tabs
under the base in the 2 provided slots, then screw
the single tab to the base using a 4mm × 6mm
screw.
12
NN-SN968B / NN-SN968BT
4.8.
Inverter power supply
6. Press 1 encircled locking tab and then slide 4 locking tabs
of Inverter bracket at the bottom of the base in direction of
arrows.
CAUTIONS
1. Always leave the grounding plate in place.
2. Always securely tighten the ground screw through the bottom of the
chassis (base).
3. Securely connect 3 lead wire connectors.
4. Make sure the heat sink has enough space (gap) from the oven.
Take special care not to dress any lead wire over the aluminum heat
sink because it is hot.
1. Discharge high voltage charge.
2. Remove the H.V.lead wire from magnetron terminals.
3. Disconnect 2 connectors from CN701 & CN702 on
H.V.Inverter(U).
4. Remove 1 screw holding grounding plate to the base.
7. Remove 1 screw holding H.V.Inverter to Inverter bracket.
5. Bend back 2 locking metal tabs on the base.
8. Remove 1 screw holding grounding plate to H.V. Inverter.
13
NN-SN968B / NN-SN968BT
5 COMPONENT TEST PROCEDURE
5.3.
WARNING
1. High voltage is present at the output terminals of the High Voltage
Inverter (U) including aluminum heat sink during any cook cycle.
2. It is neither necessary nor advisable to attempt measurement of the
high voltage.
3. Before touching any oven components, or wiring, always unplug
the power cord and discharge the high voltage capacitors (see page
8).
5.1.
Continuity checks can only indicate an open filament or a
shorted magnetron. To diagnose for an open filament or
shorted magnetron.
1. Isolate magnetron from the circuit by disconnecting the
leads.
2. A continuity check across magnetron filament terminals
should indicate one ohm or less.
Primary, Secondary Latch
Switch interlocks & Power
Relay RY1
3. A continuity check between each filament terminal and
magnetron case should read open.
1. Unplug lead connectors to Power Relay RY1 and verify
open circuit of the Power Relay RY1 1-2 terminals.
2. Unplug lead connectors to Primary Latch Switch and
Secondary Latch Switch.
3. Test the continuity of switches at door opened and closed
positions with ohm meter (low scale).
Normal continuity readings should be as follows.
Primary Latch Switch
Secondary Latch Switch
Power Relay RY1
5.2.
Door Closed
0Ω (Close)
0Ω (Close)
Ω (Open)
Door Opened
Ω(Open)
Ω(Open)
Ω(Open)
Monitor Interlock Switch
1. Unplug lead wires from Inverter Power Supply (U) primary
terminals.
2. Connect test probes of ohm meter to the disconnected
leads that were connected to Inverter Power Supply (U).
3. Test the continuity of Monitor Interlock Switch with door
opened and closed positions using lowest scale of the ohm
meter.
Normal continuity readings should be as follows.
Door Opened
0Ω (Close)
Magnetron
Door Closed
Ω (Open)
14
NN-SN968B / NN-SN968BT
5.4.
Inverter power supply (U)
5. Program oven at High power for 1 minute and press [Start]
button.
DO NOT try to REPAIR H.V. Inverter power supply (U).
Replace complete H.V. Inverter(U) Unit.
a. After approximately 3 seconds, oven stops operating.
b. During oven operation,
approximately 0.4A.
Unplug CN701
the
INPUT CURRENT
0.4A
input
current
is
FAILURE CODE
Oven stops in 3
seconds after started.
If both a and b check OK, the Inverter Power Supply (U) can be
determined to be OK.
5.5.
Temperature thermistor
The thermistor that is attached to the magnetron detects the
temperature of the magnetron and will stop magnetron
operation when overheating is detected. A normal thermistor´s
resistance is 35KΩ to 110KΩ for an ambient temperature range
of 10-30 degree C.
If the resistance reading is out of the range stated here, the
thermistor is detective and must be replaced.
It is also possible to display thermistor level by taking the
following steps.
WARNING: HIGH VOLTAGE
1. Program the DPC into TEST MODE (Plug-in oven → press
Clock pad once → press Timer pad once → press
Start button once → press Power Level pad once).
Test if failure codes H95, H97 or H98 appear when performing
the following procedure. It is recommended to use an AC line
input current ammeter for testing.
2. Program oven at Standing Time for 1 minute and press
[Start] pad.
Test 1
3. Press Power Level once, the thermistor level reading will
shown on the display.
1. With the oven unit’s AC power supply cord is unplugged
from the wall outlet, unplug the 2 pin H.V. connector CN703
from the magnetron tube.
The normal reading should be in the range of 16-230.
2. Place 1 liter of water load into oven cavity.
3. Plug in the oven’s AC power supply cord into outlet.
4. Program DPC.
a. Press Clock
pad once.
b. Press Timer
pad once.
c. Press Start
button once.
d. Press Power Level
pad once.
5. Program oven at High power for 1 minute and press [Start]
button.
a. After approximately 37 seconds, oven stops operating.
b. During oven operation, the input current is
approximately 0.5 to 1A. If both a and b are OK,
proceed to test 2.
Unplug CN703
INPUT CURRENT
0.5 to 1A
FAILURE CODE
Oven stops in 37
seconds after started.
Test 2
Continued from Test 1
1. Unplug the oven’s AC power supply cord from outlet.
2. Unplug 3 pin connector CN701. CN703 remains unplugged.
3. Plug in the oven’s AC power supply cord into outlet.
4. Program DPC.
a. Press Clock
pad once.
b. Press Timer
pad once.
c. Press Start
button once.
d. Press Power Level
pad once.
15
NN-SN968B / NN-SN968BT
6 MEASUREMENTS AND ADJUSTMENTS
6.1.
Adjustment of primary latch
switch, secondary latch switch
and monitor interlock switch.
1. Mount the Primary latch switch, the Secondary latch switch
and the Monitor interlock switch to the door hook assembly
as shown in illustration.
NOTE:
6.2.
No
specific
individual
adjustments
during
installation of the Primary latch switch, Secondary
latch switch or Monitor interlock switch to the door
hook are required.
Measurement of microwave
output
The output power of the magnetron can be determined by
performing IEC standard test procedures. However, due to the
complexity of IEC test procedures, it is recommended to test
the magnetron using the simple method outlined below.
2. When mounting the door hook assembly to the oven
assembly, adjust the door hook assembly by moving it in
the direction of the arrows in the illustration so that the oven
door will not have any play in it. Check for play in the door
by pulling the door assembly. Make sure that the latch keys
move smoothly after adjustment is completed. Completely
tighten the screws holding the door hook assembly to the
oven assembly.
Necessary Equipment:
*1 liter beaker *Glass thermometer
*Wrist watch or stopwatch
NOTE:
Check the line voltage under load. Low voltage will
lower the magnetron output. Take the temperature
readings and heating time as accurately as possible.
3. Reconnect the monitor interlock switch and check the
continuity of the monitor circuit and all latch switches again
by following the component test procedures.
1. Fill the beaker with exactly one liter of tap water. Stir the
water using the thermometer and record the water’s
temperature. (recorded as T1).
2. Place the beaker on the center of glass tray.
Set the oven for High power and heat it for exactly one
minute.
3. Stir the water again and read the temperature of the water.
(recorded as T2).
4. The normal temperature rise at High power level for each
model is as shown in table.
TABLE (1L-1min. test)
RATED OUTPUT
TEMPERATURE RISE
1200W
Min. 18.5°F(10.3°C)
1300W
Min. 19.8°F(11.1°C)
16
NN-SN968B / NN-SN968BT
7 PROCEDURE FOR MEASURING MICROWAVE ENERGY
LEAKAGE
7.2.1.
Measurement with the outer panel
removed.
Whenever you replace the magnetron, measure for radiation
leakage before the outer panel is installed and after all
necessary components are replaced or adjusted. Special care
should be taken in measuring around the magnetron.
NOTE:
7.2.2.
The U.S. Government standard is 5 mW/cm 2 while in the
customer’s home. 2mW/cm 2 stated here is our own
voluntary standard. (1mW/cm2 for Canada)
Measurements with a fully
assembled oven.
• Electromagnatic radiation monitor
After all components, including outer panel are fully assembled,
measure for radiation leakage around the door periphery, the
door viewing window, the exhaust opening, control panel and
air inlet openings.
• Glass thermometer 212°F or 100°C
7.3.
7.1.
Equipment
• 600cc glass beaker
7.2.
Procedure for measuring
radiation leakage
Record keeping and
notification after measurement
• After any adjustment or repair to a microwave oven, a
leakage reading must be taken. Record this leakage
reading on the repair ticket even if it is zero.
Note before measuring:
A copy of this repair ticket and the microwave leakage
reading should be kept by repair facility.
• Do not exceed meter full scale deflection. Leakage monitor
should initially be set to the highest scale.
• Should the radiation leakage be more than 2 mW/cm 2
(1mW/cm2 for Canada) after determining that all parts are in
good condition, functioning properly, and genuine
replacement parts as listed in this manual have been used,
immediately notify PSTC, PPR or PCI.
• To prevent false readings, the test probe should be held by
the grip portion of the handle only and moved along the
shaded area in Figure no faster than 1 inch/sec
(2.5cm/sec).
• Leakage with the outer panel removed: less than 5mW/cm 2.
• Leakage for a fully assembled oven with door normally
closed: less than 2mW/cm 2 (1mW/cm 2 for Canada).
• Leakage for a fully assembled oven [Before the latch switch
(primary) is interrupted] while pulling the door: less than
2mW/cm 2.
1. Pour 275 ± 15cc (9ozss± 1/2oz) of 20°C ± 5°C (68° ± 9°F)
water in a beaker which is graduated to 600cc, and place in
the center of the oven.
2. Set the radiation monitor to 2450MHz and use it following
the manufacturer´s recommended test procedure to assure
correct results.
3. When measuring the leakage, always use the 2 inch (5cm)
spacer supplied with the probe.
4. Tap the start button or set the timer and with the magnetron
oscillating, measure the leakage by holding the probe
perpendicular to the surface being measured.
17
NN-SN968B / NN-SN968BT
7.4.
At least once a year, have the
radiation monitor checked for
calibration by its
manufacturer.
18
NN-SN968B / NN-SN968BT
8 TROUBLESHOOTING GUIDE
DANGER: HIGH VOLTAGES
1. DO NOT RE-ADJUST PRESET CONTROL on the H.V.Inverter (U). It is very dangerous to repair or adjust without proper test equipment
because this circuit generates very large current and high voltage. Operating a misaligned inverter circuit is dangerous.
2. Ensure proper grounding before troubleshooting.
3. Be careful of the high voltage circuitry, taking necessary precautions when troubleshooting.
4. Discharge high voltage remaining in the H.V.Inverter (U).
5. When checking the continuity of the switches or the H.V.Inverter, disconnect one lead wire from these parts and then check continuity with the
AC plug removed. Doing otherwise may result in a false reading or damage to your meter. When disconnecting a plastic connector from a
terminal, you must hold the plastic connector instead of the lead wire and then disconnect it, otherwise lead wire may be damaged or the
connector cannot be removed.
6. Do not touch any parts of the circuitry on the digital programmer circuit, since static electric discharge may damage this control panel. Always
touch ground while working on this panel to discharge any static charge in your body.
7. 120V AC is present on the digital programmer circuit (Terminals of power relay’s and primary circuit of Digital Programmer Circuit). When
troubleshooting, be cautious of possible electrical shock hazard.
Before troubleshooting, operate the microwave oven following the correct operating procedures in the instruction manual in order
to find the exact cause of any trouble, since operator error may be mistaken for the oven’s malfunction.
8.1.
(Troubleshooting) Oven stops operation during cooking
SYMPTOM
1. Oven stops in 3 seconds
pressing [Start] button
CAUSE
CORRECTIONS
after No 120V AC is supplied to H.V.Inverter (U) CN702 1. Latch Switch
terminals
2. Power relay RY1
3. Loose lead wire connector CN701, CN702
4. H.V. Inverter (U)
Oven stops in 37 seconds after H.V.Inverter (U) operates by the control signals 1. Magnetron
pressing [Start] button
from DPC but magnetron is not oscillating
2. Loose lead wire connector CN703
3. H.V. Inverter (U)
Oven stops in 10 seconds after Steam sensor circuit is not functioning
1. Steam sensor
pressing [Start] button
2. DPC
(Auto sensor cooking)
3. Open or loose wiring of sensor terminal
from connector CN2 on DPC
2. No display and no operation at all.
Most probably loose connection of connectors, or 1. Allign door, Door Latch Switches
Fuse is blown.
door latch mechanism is not adjusted properly
2. Loose wiring connectors
19
NN-SN968B / NN-SN968BT
8.2.
(Troubleshooting) Other problems
SYMPTOM
1. Oven is dead.
Fuse is OK.
No display and no operation at all.
2. No display and no operation at all.
Fuse is blown.
3. Oven does not accept key input
(Program)
4. Fan motor turns on when oven is
plugged in with door closed.
5. Timer starts count down but no
microwave oscillation.
(No heat while oven lamp and fan
motor turn on)
1.
2.
3.
4.
1.
2.
3.
4.
1.
2.
3.
4.
1.
2.
3.
1.
2.
3.
6. Oven can program but timer does not
start countdown.
7. Microwave output is low. Oven takes
longer time to cook food.
8. Fan motor turns on and turntable
motor rotates when door is opened.
9. Oven does not operate and return to
plugged in mode as soon as [Start]
button is pressed.
10. Loud buzzing noise can be heard.
11. Turntable motor does not rotate.
12. Oven stops operation during cooking.
4.
5.
6.
1.
2.
3.
1.
2.
3.
1.
CAUSE
CORRECTIONS
Open or loose lead wire harness
Open thermal cutout / thermistor
Check thermal cutout is defective.
Open low voltage transformer
Defective DPC
Shorted lead wire harness
Check adjustment of primary, secondary latch
switch and monitor interlock switch including
Defective primary latch switch (NOTE 1)
door.
Defective monitor interlock switch (NOTE 1)
Defective Inverter Power Supply (U)
NOTE 1:
All of these switches must be replaced at the same time.
Check continuity of power relay RY1 contacts (between 1 and 2) and if it has continuity, replace
power relay RY1 also.
Key input is not in proper sequence
Refer to operation procedure.
Open or loose connection of membrane key
button to DPC (Flat cable)
Shorted or open membrane key board
Defective DPC
Refer to DPC troubleshooting.
Misadjustment or loose wiring of secondary
Adjust door and latch switches.
latch switch
Defective secondary latch switch
Door switch CN3
Off-alignment of primary latch switch
Adjust door and latch switches.
Open or loose connection of high voltage
circuit especially magnetron filament circuit
NOTE:
Large contact resistance will cause lower
magnetron filament voltage and cause
magnetron to have lower output and/or be
intermittent.
Defective high voltage component
Check high voltage component according to
H.V. Inverter Power Supply (U)
component test procedure and replace if it is
Magnetron
defective.
Open or loose wiring of power relay RY1
Defective primary latch switch
Defective DPC or power relay RY1
Refer to DPC troubleshooting
Open or loose wiring of secondary latch switch
Off-alignment of secondary latch switch
Defective secondary latch switch
Decrease in power source voltage
Consult electrician
Open or loose wiring of magnetron filament
circuit. (Intermittent oscillation)
Aging change of magnetron
Low voltage transformer on DPC.
1. Defective DPC
Check grounding connector on escutcheon
base.
1.
1.
2.
1.
Loose fan and fan motor
Open or loose wiring of turntable motor
Defective turntable motor
Open or loose wiring of primary and
secondary latch switch
2. Operation of thermal cutout
20
Adjust door and latch switches.
NN-SN968B / NN-SN968BT
8.3.
Troubleshooting of inverter circuit (U) and magnetron
This oven is programmed with a self diagnostics failure code system which will help for troubleshooting. H95, H97, H98 and H99
are the provided failure codes to indicate magnetron and inverter circuit problem areas. This section explains failure codes of H95,
H97, H98 and H99. First, you must program the DPC into TEST MODE, press Clock pad once → press Timer pad once →
Press Start button once → press Power Level pad once. Program unit for operation. H95, H97, H98, H99 appears in display
window a short time after [Start] button is pressed and there is no microwave oscillation.
Alternate way to troubleshoot oven with AC Ampere meter used
H95, H97, H98, H99 appears in display window a short time after [Start] button is pressed and no microwave oscillation with AC
Ampere meter used for troubleshooting.
21
NN-SN968B / NN-SN968BT
8.4.
Trouble related to Digital Programmer Circuit
SYMPTOM
No display when oven is first plugged
in
STEP
CHECK
1
Fuse pattern of D.P.C.
2
RESULT
Normal
CAUSE/CORRECTIONS
→Step2
Open
Replace D.P.C. or Fuse
Pattern
L.V.T.
→Step3
Q11, ZD11, Q10, ZD10
IC1, CX320, Display
Button switch / membrane
switch
IC1
IC1
BZ310, Q224
IC1
→Step2
Q223
RY2
IC1
→Step2
Q220 and/or Q221, Q222,
Q225
RY1
Display
IC1
IC1
Display
1. Latch Switch
2. D.P.C. /Power Relay
→Step2
D.P.C.
Magnetron
No key input
1
Abnormal 0V
Normal
IC1 pin 23 voltage
Abnormal
Normal=3.3V
Button switch / membrane switch continuity Abnormal
No beep sound
1
IC1 pin 29 voltage
Power relay RY2 does not turn on
even though the program had been set
and the start button is tapped
1
IC1 pin 2 voltage while operation
2
Collector of Q223 voltage
No microwave oscillation at any power
1
IC1 pin 1 voltages while operation at high
power
2
Collector of Q220 voltage
Dark or unclear display
1
Replace display and check operation
Missing or lighting of unnecessary
segment
1
Replace IC1 and check operation
H95/H97/H98 appears in window and
oven stops operation.Program High
power for 1 minute and conduct
following test quickly, unless
H95/H97/H98 appears and oven stops
1
Unplug CN702 (2 pin) connector and
measure voltage between terminals
2
Unplug CN701 (3 pin) connector and
measure pin1 voltage of connector CN3
3
Low voltage transforment (L.V.T.)
secondary voltage
22
Normal
Abnormal
Normal=3.3V
Abnormal
Normal=3.3V
Abnormal
Normal 0.7V
Abnormal
Normal=3.3V
Abnormal
Normal 0.7V
Normal
Abnormal
Normal
Abnormal
Abnormal=0V
Normal=120V
Abnormal=0V
Approx. AC 3V
NN-SN968B / NN-SN968BT
8.5.
SIMPLE WAY OF H.V. INVERTER/MAGNETRON TROUBLESHOOTING
Purpose:
Simple way (3/37 seconds rule) of identifying whether it’s Magnetron, Inverter or others.
Set-up:
The unit under question is connected through the Ammeter as shown below.
Procedure:
Follow the matrix table below to identify the problem source.
Note:
Do not replace both Inverter board and Magnetron simultaneously and automatically without going through this
procedure.
Power will:
Ammeter reading is:
Shut off in 37 seconds 1. Between 0.5A and 1.0A.
after “Start”.
2. Between 1.0A and 2.0A.
To do:
Remedy:
Check and repair open magnetron circuit Open magnetron wiring between Inverter
and magnetron terminal.
Check continuity of D702 in Inverter PCB.
Shut off in 3 seconds 1. Less than 0.5A
after “Start”
1. D702 shorted
Replace H.V.Inverter(F606Y8X00AP)
2. D702 is OK
Replace magnetron
Check open circuit: Latch Switch, DPC, Replace defective component(s), or
Power Relay and CN701
correct switch, cables and connectors.
8.6.
Ref. No.
DB701
L701
Q701
T701
C701
C702
H.V.INVERTER BOARD MAIN PARTS LIST (F606Y8X00AP)
Part No.
B0FBBQ000007
F5020W100AP
B1JAGV000015
A609A8X00AP
F0C2H284A012
F0C2E455A246
Part Name & Description
BRIDGE DIODE
CHOKE COIL
TRANSISTOR SI
H.V. TRANSFORMER
CAPACITOR
CAPACITOR
23
Pcs/Set
1
1
1
1
1
1
Remarks
20A,600V
1000V
0.28µF/500VDC
4.5µF/250VDC
NN-SN968B / NN-SN968BT
8.7.
How to check the semiconductors using an OHM meter
24
NN-SN968B / NN-SN968BT
9 EXPLODED VIEW AND PARTS LIST
9.1.
EXPLODED VIEW
25
NN-SN968B / NN-SN968BT
9.2.
PARTS LIST
NOTE:
1. When ordering replacement part(s), please use part number(s) shown in this part list.
Do not use description of the part.
2. Important safety notice:
Components identified by
mark have special characteristics important for safety.
When replacing any of these components, use only manufacture’s specified parts.
Ref. No.
1
3
4
5
Part No.
F00069660AP
F00338F00AP
F10016P40AP
F10084T00APS
Part Name & Description
CAUTION LABEL
FUSE LABEL
BASE
RUBBER FOOT
Pcs/Set
1
1
1
4
6
7
8
9
10
F10095W20BAP
F200A8D00AP
F20555K00AP
F21315Y00AP
F2177-F80
CABINET BODY
OVEN
COVER
PULLY SHAFT
WASHER
1
1
1
1
1
11
12
14
15
F290D9330AP
F3020-1200
F3136-1200
F31374650AP
ROLLER RING (U)
DOOR HOOK
HOOK LEVER A
HOOK LEVER B
1
1
1
1
16
17
18
19
20
F31384650AP
F400A5Y00AP
F40084T00AP
F40254W00AP
F40264T60APG
HOOK LEVER C
FAN MOTOR
FAN BLADE
AIR GUIDE A
AIR GUIDE B
1
1
1
1
1
21
22
24
25
F41445W00AP
F64508660AP
F65434W00AP
J607S4M00AP
ORIFICE
SENSOR COVER B
SENSOR COVER C
STEAM SENSOR
1
1
1
1
26
27
28
29
F612E5Y30AP
J61415G10XN
F61415U30XN
F61456N60AP
INCANDESCENT LAMP (U)
MICRO SWITCH
MICRO SWITCH
THERMAL CUTOUT
1
1
1
1
125V,60Hz
(PRIMARY LATCH SWITCH)
(SECONDARY LATCH SWITCH)
150°C/-20°C
31
32
33
34
35
F61785U30XN
F606Y8X00AP
F65856K50AP
2M261-M32KLP
F62308F20AP
MICRO SWITCH
H.V.INVERTER (U)
INVERTER BRACKET
MAGNETRON
FUSE
1
1
1
1
1
(MONITOR INTERLOCK SWITCH)
37
38
39
40
F692Y8F00APX
F63265G60AP
F900C4T00AP
F66626G10AP
NOISE FILTER
TURNTABLE MOTOR
AC CORD W/PLUG
GROUNDING PLATE
1
1
1
1
41
42
43
44
XTWFL4+12T
F90804W00AP
XTTBFE4T10A0
XTTFA4+6BFZ
SCREW
CANOE CLIP
SCREW
SCREW
4
1
5
2
47
48
50
F03347D60AP
F82575W00AP
F00067C50AP
MENU LABEL
DOOR OPENING BRACKET
CAUTION LABEL
1
1
1
52
55
F00318Y00AP
F00078W70BAP
POWER LABEL
NAME PLATE
1
1
26
Remarks
AC120V,SINGLE PHASE,60Hz
20A
FOR
FOR
FOR
FOR
MAGNETRON
COVER
CABINET BODY
CABINET BODY SIDE
NN-SN968B / NN-SN968BT
9.3.
ESCUTCHEON BASE ASSEMBLY
Ref. No.
E1
E2
E3
E4
E5
Part No.
F603L8W70AP
F603Y8W70AP
F80347B00BAP
F66164W20AP
F82987D60KAP
Part Name & Description
D.P.CIRCUIT (AU)
D.P.CIRCUIT (DU)
ESCUTCHEON BASE
FLAT CABLE
BUTTON
E6
E7
E8
E9
F80726G40BAP
F82565W00AP
F80375K00AP
F630Y8W70BAP
DOOR OPENING BUTTON
DOOR OPENING LEVER
COOK BUTTON SPRING
MEMBRANE SWITCH (U)
Pcs/Set
1
1
1
1
1
1
1
1
1
27
Remarks
NN-SN968B / NN-SN968BT
9.4.
DOOR ASSEMBLY
Ref. No.
D1
D2
D3
D4
D5
Part No.
F30186P40AG
F30016G40BAP
F302K4U00AP
F30215G10XN
F30854U00AP
Part Name & Description
DOOR KEY A
DOOR A
DOOR E (U)
DOOR KEY SPRING
DOOR C
D6
D7
F31454U00AP
F31468P40BAP
DOOR SCREEN A
DOOR SCREEN B
Pcs/Set
1
1
1
1
1
1
1
28
Remarks
NN-SN968B / NN-SN968BT
9.5.
Ref. No.
W1
W2
W3
WIRING MATERIALS
Part No.
F030A7B80AP
F030E8W50AP
F03537B70AP
Part Name & Description
LEAD WIRE HARNESS
H.V.LEAD WIRE
LEAD WIRE HARNESS (U)
Pcs/Set
Remarks
1
1
1
(INCLUDING THERMISTOR)
29
NN-SN968B / NN-SN968BT
9.6.
PACKING AND ACCESSORIES
Ref. No.
P1
P2
P2
P3
P4
P5
Part No.
F00038W70AP
F01028W70BAP
F01028W70APT
F01045J00AP
F01055J00AP
F01067C50AP
Part Name & Description
INSTRUCTION MANUAL
PACKING CASE,PAPER
PACKING CASE,PAPER
UPPER FILLER
LOWER FILLER
P.E.BAG
P6
P7
P8
P9
P10
F01074U00AP
F06014M00AP
F01084M00AP
F01924U00AP
F00065G40AP
DOOR SHEET
COOKING TRAY
TRAY PACKING
SHEET
CAUTION LABEL
Pcs/Set
1
1
SN968B APH
1
SN968BT APH
1
1
1
1
1
1
1
1
30
Remarks
NN-SN968B / NN-SN968BT
10 DIGITAL PROGRAMMER CIRCUIT
10.1. SCHEMATIC DIAGRAM
31
NN-SN968B / NN-SN968BT
32
NN-SN968B / NN-SN968BT
10.2. PARTS LIST
Ref. No.
BZ310
C10
C13,C16
C482
C483
C485
CX320
DISP110
DISP HOLDER
D40,D226,D227
D10-D13
D220,D221,D223,D225
D480
IC1
IC350
IC480
Q10,Q180
D25
RY1
RY2
T10
VZ340
SW1,SW2,SW10,SW12,SW13
ZD10
ZD11
Part No.
L0DDEA000014
F2A1V471B281
F2A1C220B624
F2A1H1R0B574
F2A1HR47B574
F2A1H2R2B574
H2B800400007
L5AAAEC00061
F66177D60AP
MA2C19600E
B0EAKT000025
MA2C19600E
MA2C700A0F
MN101C78AEH
C0EBE0000401
C0ABBA000230
B1BAAJ000003
D4EAY271A036
AEBGJQC25F18
K6B1AZA00010
G4C2AAD00005
D3CA6103A017
EVQ11L05R
B0BA5R600016
B0BA4R400002
Part Name & Description
BUZZER
AL CHEM CAPACITOR
AL CHEM CAPACITOR
AL CHEM CAPACITOR
AL CHEM CAPACITOR
AL CHEM CAPACITOR
CERAMIC RESONATOR
LCD
LCD HOLDER
DIODE
DIODE
DIODE
DIODE
L.S.I.
IC
IC
TRANSISTOR
ZENER RESISTOR
POWER RELAY
POWER RELAY
LOW VOLTAGE TRANSFORMER
VARISTOR
SWITCH
ZENER DIODE
ZENER DIODE
33
Pcs/Set
1
1
2
1
1
1
1
1
1
3
4
4
1
1
1
1
2
1
1
1
1
1
5
1
1
Remarks
2.0KHz
470µF/35V
22µF/16V
1µF/50V
0.47µF/50V
2.2µF/16V
8.0MHz
270V
120V
10KΩ
12/09
S-8W7
Printed in China