Panasonic Nn St452w User Manual

							4.3. Low voltage transformer
and/or power relays (RY1,
RY2)
CAUTION:
Be sure to ground any static electric charge built up in
your body before handling the DPC.
 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.
CAUTION:
Do not use a soldering iron or desoldering tool of
more than 30 watts on D.P.C. contacts.
(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. Fan motor
 1. Disconnect 2 lead wires from fan motor terminals.
 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.
 5. Remove 2 screws holding fan motor to orifice.
4.5. Door assembly
 1. Support the door, remove 3 screws holding hinge A.
 2. Open the door, remove door(U) and hinge A from cavity.
NOTE:
Support the door before opening.
 3. Remove door C from door A (U) & door E by carefully
pulling outward starting from upper right hand corner using
a flat blade screwdriver.
 4. Separate door E from tabs on door A (U) and remove door
A (U).
 5. Remove door key and door key spring from door E.
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							 6. Replace other components.
To re-install components:
NOTE:
After replacement of the defective component parts
of the door, reassemble it properly and adjustment
so as to prevent an excessive microwave leakage.
Adjustment of the door assembly (Refer page 17).
 7. Place the hole of hinge A into the door’s upper hinge pin.
 8. Use your left index finger to support the door’s lower hinge
pin while guiding the door’s hinge A into the cavity slot.
Then lower your finger to seat the door onto the hinge.
NOTE:
Door alignment is crucial. If door is misaligned,
apply pressure until alignment is achieved.
NOTE:
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. 9. Tighten 2 mounting screws.
Be sure the gap between door E and cavity front plate will
be 0.3~0.7mm.
NOTE:
Always perform the microwave leakage measurement
test after installation and adjustment of door assembly.
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							4.6. Turntable motor
 1. Remove the motor cover by breaking off at the 8 spots
indicated by arrows with a cutter or the like.
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 the turntable motor by removing screw.
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.
4.7. Steam sensor
 1. Disconnect connector CN2 from digital programmer circuit
board.
 2. Disengage catch hooks on sensor cover C from orifice.
 3. Remove steam sensor from orifice.
NOTE:
When installing the steam sensor, make sure that
the direction of steam sensor is as shown in figure.
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							4.8. Inverter power supply
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.
 5. Press 1 encircled locking tab and then slide 4 locking tabs
of Inverter bracket at the bottom of the base in direction of
arrows.
 6. Remove 1 screw holding H.V.Inverter to Inverter bracket.
 7. Remove 1 screw holding grounding plate to H.V. Inverter.
 8. Seperate H.V. Inverter from Inverter bracket by freeing 3
catch hooks on the Inverter bracket.
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							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. Primary, Secondary Latch
Switch interlocks & Power
Relay RY1
 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.
Door ClosedDoor Opened
Primary Latch Switch0Ω(Close)Ω(Open)
Secondary Latch Switch0Ω(Close)Ω(Open)
Power Relay RY1Ω(Open)Ω(Open)
5.2. Short 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 short switch with door opened and
closed positions using lowest scale of the ohm meter.
Normal continuity readings should be as follows.
Door OpenedDoor Closed
0Ω(Close)Ω(Open)
5.3. Magnetron
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.
 3. A continuity check between each filament terminal and
magnetron case should read open.
5.4. key board membrane
(Membrane switch assembly)
Check continuity between switch terminals, by tapping an
appropriate pad on the key board. The contacts assignment of
the respective pads on the key board is as shown in digital
programmer circuit.
5 COMPONENT TEST PROCEDURE
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							5.5. Inverter power supply (U)
DO NOT try to REPAIR H.V. Inverter power supply
(U).Replace complete H.V. Inverter(U) Unit.
WARNING: HIGH VOLTAGE
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.
Test 1
 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.
 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.
For SD452W model
 a. Press Clock
button once.
 b. Press Timer
button once.
 c. Press Start
button once.
 d. Press 1000W/600W
button once.
For ST462M & ST452W models
 a. Press Timer
pad twice.
 b. Press Start
pad once.
 c. Press Micro Power
pad once.
 5. Program oven at High power for 1 minute and press [Start]
pad.
 a. After approximately 23 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.
INPUT CURRENTFAILURE CODE
Unplug CN7030.5 to 1AOven stops in 23
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.
For SD452W model
 a. Press Clock
button once.
 b. Press Timer
button once.
 c. Press Start
button once.
 d. Press 1000W/600W
button once.
For ST462M & ST452W models
 a. Press Timer
pad twice.
 b. Press Start
pad once.
 c. Press Micro Power
pad once.
 5. Program oven at High power for 1 minute and press [Start]
pad.
 a. After approximately 3 seconds, oven stops operating.
 b. During oven operation, the input current is
approximately 0.4A.
INPUT CURRENTFAILURE CODE
Unplug CN7010.4AOven stops in 3
seconds after started.
If both a and b check OK, the Inverter Power Supply (U) can be
determined to be OK.
5.6. 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 35KΩto 110KΩfor 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.
For SD452W model
 1. Program the DPC into TEST MODE (Plug-in oven→press
Clock
button once→press Timerbutton once→press
Start
button once→press 1000W/600Wbutton once).
 2. Program oven at Standing Time for 1 minute and press
[Start] button.
 3. Press Sensor Reheat
once, the thermistor level reading
will shown on the display.
The normal reading should be in the range of 16-230.
For ST462M & ST452W models
 1. Program the DPC into TEST MODE (Plug-in oven→press
Timer
pad twice→press Startpad once→press
Micro Power
pad once).
 2. Program oven at Standing Time for 1 minute and press
[Start] pad.
 3. Press Reheat
twice, the thermistor level reading will
shown on the display.
The normal reading should be in the range of 16-230.
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							6.1. Adjustment of primary latch
switch, secondary latch switch
and short switch.
 1. Mount the Primary latch switch, the Secondary latch switch
and the Short switch to the door hook assembly as shown
in illustration.
NOTE:
No specific individual adjustments during
installation of the Primary latch switch, Secondary
latch switch or Short switch to the door hook are
required.
 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.
 3. Reconnect the short switch and check the continuity of the
monitor circuit and all latch switches again by following the
component test procedures.
6.2. 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.
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.
 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 OUTPUTTEMPERATURE RISE
1000WMin. 8.5°C
6 MEASUREMENTS AND ADJUSTMENTS
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							7 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.
7.230-240V 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.
7.1. (Troubleshooting) Oven stops operation during cooking
SYMPTOMCAUSECORRECTIONS
1.
.Oven stops in 3 secondsafter
pressing [Start] button.No input AC is supplied to H.V.Inverter (U)
CN702 terminals1. Latch Switch
2. Power relay RY1
3. Loose lead wire connector CN701, CN702
4. H.V. Inverter (U)
Oven stops in 23 secondsafter
pressing [Start] button.H.V.Inverter (U) operates by the control signals
from DPC but magnetron is not oscillating1. Magnetron
2. Loose lead wire connector CN703
3. H.V. Inverter (U)
Oven stops in 10 secondsafter
pressing [Start] button.
(Auto sensor cooking)Steam sensor circuit is not functioning1. Steam sensor
2. DPC
3. Open or loose wiring of sensor terminal from
connector CN2 on DPC
2.No display and no operation at all.
Fuse is blown.Most probably loose connection of connectors, or
door latch mechanism is not adjusted properly1. Align door, Door Latch Switches
2. Loose wiring connectors
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							7.2. (Troubleshooting) Other problems
SYMPTOMCAUSECORRECTIONS
1.Oven is dead.1.Open or loose lead wire harness
Fuse is OK.2.Open thermal cutout / thermistorCheck thermal cutout is defective.
No display and no operation at all.3.Open low voltage transformer
4.Defective DPC
2.No display and no operation at all.
Fuse is blown.1.Shorted lead wire harnessCheck adjustment of primary, secondary latch
switch and short switch including door.
2.Defective primary latch switch (NOTE 1)
3.Defective short switch (NOTE 1)
4.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.
3.Oven does not accept key input
(Program)1.Key input is not in proper sequenceRefer to operation procedure.
2.Open or loose connection of membrane key
button to DPC (Flat cable)
3.Shorted or open membrane key board
4.Defective DPCRefer to DPC troubleshooting.
4.Fan motor turns on when oven is
plugged in with door closed.1.Misadjustment or loose wiring of secondary
latch switchAdjust door and latch switches.
2.Defective secondary latch switch
3.Door switch CN12
5.Timer starts count down but no
microwave oscillation.
(No heat while oven lamp and fan
motor turn on)1.Off-alignment of primary latch switchAdjust door and latch switches.
2.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.
3.Defective high voltage component
H.V. Inverter Power Supply (U)
MagnetronCheck high voltage component according to
component test procedure and replace if it is
defective.
4.Open or loose wiring of power relay RY1
5.Defective primary latch switch
6.Defective DPC or power relay RY1Refer to DPC troubleshooting
6.Oven can program but timer does not
start countdown.1.Open or loose wiring of secondary latch switch
2.Off-alignment of secondary latch switch
3.Defective secondary latch switch
7.Microwave output is low. Oven takes
longer time to cook food.1.Decrease in power source voltageConsult electrician
2.Open or loose wiring of magnetron filament
circuit.(Intermittent oscillation)
3.Aging change of magnetron
8.Fan motor turns on and turntable
motor rotates when door is opened.1.Low voltage transformer on DPC.
9.Oven does not operate and return to
plugged in mode as soon as [Start]
button is pressed.1.Defective DPCCheck grounding connector on escutcheon
base.
10.Loud buzzing noise can be heard.1.Loose fan and fan motor
11.Oven stops operation during cooking.1.Open or loose wiring of primary and
secondary latch switchAdjust door and latch switches.
2.Operation of thermal cutout
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							7.3. 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,For SD452W model:press Clock
button once→press
Timer
button once→press Startbutton once→press 1000W/600Wbutton once,For ST462M & ST452W model:press
Timer
pad twice→press Startpad once→press Micro Powerpad once. Program unit for operation. H95, H97, H98, H99
appears in display window a short time after [Start] pad 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.
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NN-SD452W / NN-ST462M / NN-ST452W