Panasonic NN-T259WB User manual

ORDER NO. MOP9905002C2
© 1999 Matsushita Electric Industrial Co., Ltd.
All ri
g
hts reserved. Unauthorized cop
y
in
g
and
distribution is a violation of law.
Service Manual
Microwave Oven
NN-T259WB
NN-T259CB
Specifications:
Power Source: 240 V AC Sin
g
le Phase, 50 Hz
Power Re
q
uirements: Microwave: 1100W
Output:
(
IEC705-88
)
900W
Microwave Fre
q
uenc
y
: 2,450Mhz
Timer: 99 min. 99 sec.
Oven Cavit
y
Size: 20L
Outside Dimensions: 458mm
(
W
)
X 315mm
(
D
)
X 299mm
(
H
)
Inside Dimensions: 315mm
(
W
)
X 298mm
(
D
)
X 208mm
(
H
)
Wei
g
ht: 11 K
g
Inverter Power Suppl
y
Output power: IEC705-88 Test procedure
Specifications sub
j
ect to chan
g
e without notice

2
DANGER OF HIGH VOLTAGE AND HIGH TEMPERATURE (HOT/LIVE) OF THE INVERTER POWER SUPPLY(U)
WARNING
This service information is designed for experienced repair technicians only and is not designed for use by the general public. It does not contain
warnings or cautions to advise non-technical individuals of potential dangers in attempting to service a product. Products powered by electricity
should be serviced or repaired only by experienced professional technicians. Any attempt to service or repair the product dealt with in this service
information by anyone else could result in serious injury or death.
WARNING
* This product should be serviced only by trained, qualified personnel.
This service manual covers products for following markets.
When troubleshooting or replacing parts, please refer to the country identifications shown below for your applicable product specification.
BPQ ... for the United Kingdom
INVERTER WARNING
This Inverter board looks like a regular PCB, however, this PCB drives the magnetron tube with extremely high voltage and high current.
IT HAS: 1: Very high voltage and high current circuit.
It functions the same as the high voltage transformer and high voltage capacitor in ordinary microwave ovens.
2. aluminium heat sink is very hot in high voltages and heat energy.
3. Very high voltage may remain in the circuitry even when the oven is off. High voltages may remain in the capacitors on the board.
DO NOT: *1. Do not touch the circuitry as it becomes very hot (high voltage). Even when replacing board, extreme care should be taken toavoid
possible electric shock hazards. High voltage may remain in the circuit.
*2. Do not touch aluminium heat sink because it is very hot in high voltage and also very hot in high heat energy.
*3. Do not try to repair the Inverter PCB as this can be very dangerous. Replace the whole High Voltage Inverter Circuit(U) unit and
return fully re-packed with the original shopping box and shipping materials.
*4. Do not try to adjust or tamper with the preset volume on the Inverter board because it is very dangerous to adjust it without proper
test equipment.
*5. Do not test oven while Inverter grounding strip or screws are loose. It is very dangerous to operate the H.V. Inverter Circuit (U) with
loose mounting screws or if improperly grounded.
INVERTER POWER SUPPLY DIAGRAM
NEW H.V.
HIGH VOLTAGE AREA*1
DO NOT TOUCH (HOT/HIGH VOLTAGE) *2
HEAT SINK (RECTIFIER BRIDGE)
CHOKE COIL
SAND BAR RESISTOR
CUSTOM I.C.
PHOTO COUPLER
CN 701
CURRENT TRANSFORMER
DO NOT TOUCH *4
HIGH VOLTAGE
PRIMARY WINDINGS
SECONDARY WINDINGS
HIGH VOLTAGE DIODES
CN 703
HIGH VOLTAGE CAPACITORS
DO NOT REPAIR. REPLACE WHOLE H.V.INVERTER(U)
H.V. INVERTER(U) *3
LEAD WIRE
GROUNDING PLATE *5
INVERTER WARNING
INVERTER SUPPORT
BRACKET
LABEL
FILM CAPACITORS
TRANSFORMER

3
TABLE OF CONTENTS
1. CONTROL PANELS................................................................................................................................................. 4
2. OPERATION AND DIGITAL PROGRAMMER CIRCUIT TEST PROCEDURE ....................................................... 5
3. SCHEMATIC DIAGRAM........................................................................................................................................... 7
4. DESCRIPTION OF OPERATING SEQUENCE........................................................................................................ 9
4.1 Variable power cooking control........................................................................................................................ 9
4.2 Autoweight defrost, autoweight cook................................................................................................................ 9
5. CAUTIONS TO BE OBSERVED WHEN TROUBLESHOOTING........................................................................... 10
5.1 Check the grounding...................................................................................................................................... 10
5.2 Inverter Warnings .......................................................................................................................................... 10
5.3 When parts must be replaced, remove the power plug from the outlet.......................................................... 10
5.4 When the 10A fuse is blown due to the operation of short switch:................................................................. 11
5.5 Avoid inserting nails, wire, etc. through any holes in the unit during operation.............................................. 11
5.6 Confirm after repair ........................................................................................................................................ 11
5.7 Sharp edges................................................................................................................................................... 11
6. DISASSEMBLY AND PARTS REPLACEMENT PROCEDURE............................................................................ 12
6.1 Magnetron...................................................................................................................................................... 12
6.2 Inverter Power Supply(U) .............................................................................................................................. 12
6.3 Digital Programmer Circuit (DPC) and membrane key board........................................................................ 13
6.4 Low voltage transformer and/or power relays (RY1)...................................................................................... 13
6.5 Fan Motor....................................................................................................................................................... 13
6.6 Temp sensor (thermal protector).................................................................................................................... 13
6.7 Door disassembly........................................................................................................................................... 14
6.8 Turntable motor.............................................................................................................................................. 14
7. COMPONENT TEST PROCEDURE....................................................................................................................... 15
7.1 Primary Latch Switch, Secondary (Secondary Latch Switch and Power Relay B) Interlocks........................ 15
7.2 Short Switch & Monitor Circuit ....................................................................................................................... 15
7.3 Magnetron...................................................................................................................................................... 15
7.4 Push button key board ................................................................................................................................... 15
7.5 Inverter Power Supply (U).............................................................................................................................. 16
7.6 Inverter Power supply(U) ............................................................................................................................... 16
7.7 Temp sensor (Thermal protector)................................................................................................................... 16
8. MEASUREMENTS AND ADJUSTMENTS............................................................................................................. 17
8.1 Installation of Primary latch switch, Secondary latch switch and Short switch............................................... 17
8.2 Measurement of microwave output................................................................................................................ 17
9. TROUBLESHOOTING GUIDE .............................................................................................................................. 18
10. EXPLODED VIEW AND PARTS LIST.................................................................................................................... 22
11. PARTS LISTS......................................................................................................................................................... 23
12. DOOR ASSEMBLY................................................................................................................................................. 24
13. ESCUTCHEON BASE ASSEMBLY ....................................................................................................................... 25
14. PACKING AND ACCESSORIES............................................................................................................................ 26
15. DIGITAL PROGRAMMER CIRCUIT....................................................................................................................... 28
16. DIGITAL PROGRAMMER CIRCUIT - PARTS LIST .............................................................................................. 30
FEATURE CHART
FEATURES
Microwave 6
Weight Defrost 3
Weight Reheat 2
Weight Cook 1
Stage Cooking 3 stage
Delay Stand Yes
Clock 12 Hrs
Word Prompt English

4
1. CONTROL PANELS
Beep Sound
A beep sounds when a button is pressed. If this beep does not sound, the setting is incorrect. When the oven
changes from one function to another , two beeps sound. After completion of cooking, five beeps sound
(1) Display Window
(2) Time Pads
(3) Auto Weight Microwave Program
(4) Auto Weight Defrost Programs
(5) Microwave Power Settings
(6) Delay/Stand Pad:
This can be used to delay a cooking program
for up to 9 hrs 99 mins., or used to time or for
standing (non-cooking) time.
(7) Clock Pad:
Press the clock pad. Using the minute and
second pads set the clock (12 hr clock).
Press clock pad again to stop colons flashing.
(8) lb/oz Conversion Pad
(9) Weight Selection Pads
(10) Stop/Cancel Button:
Before Cooking:
One press clears your instructions.
During Cooking:
One press temporarily stops the cooking
program. Another press cancels all your
instructions and the time of day will appear in
the display.
(11) Start Button:
Press to start operating the oven. If during
cooking the door is opened or Stop/Cancel
Button is pressed once. Start Button has to
be pressed again to continue cooking.
(1)
(2)
(5)
(6)
(7)
(10)
(11)
(9)
(8)
(4)
(3)

5
2. OPERATION AND DIGITAL PROGRAMMER CIRCUIT TEST PROCEDURE
Operation guide on the display.
To assist in programming, the next operation will appear on the display. When you are used to operating the oven, you can turn the
operating guide off.
To turn off: To turn on:
Press 3 times Press 3 times
1. SET CLOCK
2. MICROWAVE COOKING - 2 STAGE 3. AUTO WEIGHT DEFROST
OPERATING GUIDE OFF OPERATING GUIDE ON
delay/
stand
delay/
stand
OPERATION DISPLAY
1. Plug the power supply cord
into the wall outlet
WELCOME TO PANASONIC. REFER
TO OPERATING INSTRUCTIONS
2. Press clock pad
SET TIME
3. Enter time of day
4. Press clock
11:25
OPERATION DISPLAY
1. Place water load in oven
2. Press High once to set High
Power
HIGH
SET TIME
3. Set time at 5 sec by pressing
1 sec pad 5 times
4. Press Medium to set Medium
Power
Once
Once
Twice 5 Times
11
PRESS CLOCK
25
5 Times
5 SEC
PRESS START
HIGH
SET TIME
MEDIUM
5. Set for 1 minute by pressing
1min pad once
6. Press start pad
7. When 1st stage cooking has
elapsed oven automatically
switches to 2nd stage
8. When 2nd stage cooking has
elapsed oven beeps 5 times
and shuts off
ENJOY YOUR MEAL
OPERATION DISPLAY
1. Select desired program
MEAT ITEMS
SET WEIGHT
2. Press g or lb and oz
LB OZ
MEAT ITEMS
SET WEIGHT
3. Enter the weight by pressing
up and down pads
1LB OZ
PRESS START
4. Press start pad
OPERATION DISPLAY
Once
PRESS START
MIN SEC
100
MEDIUM
5
SEC
MIN SEC
100
* *
g/
lb
oz
* *
* *
* *
MIN SEC
908

6
4. DELAY STAND
5. DELAY START
6. AUTOWEIGHT COOK PROGRAM
7. TO SET CHILD SAFETY LOCK
8. TO RESET CHILD LOCK
9. DEMONSTRATION MODE
10. CANCEL DEMONSTRATION MODE
OPERATION DISPLAY
1. Set power level and time
2. Press stand
STAND
SET TIME
3. Set standing time
4. Press start
OPERATION DISPLAY
1. Press delay
DELAY START
SET TIME
2. Set delay time
3. Set power level and time
4. Press start pad
OPERATION DISPLAY
1. Select auto weight program
CHILLED MEAL
SET WEIGHT
2. Press to select grams or
pounds and ounces
LB OZ
CHILLED MEAL
SET WEIGHT
3. Enter the weight
1LB OZ
PRESS START
Delay/
Stand
H 1 00
PRESS START
MIN SEC
100
MIN SEC
H1 00
Delay/
Stand
H 1 00
CHOOSE COOKING MODE
1H 00
g/ lb
oz
4. Press start
OPERATION DISPLAY
1. Press start 3 times to display
lock
* LOCK
OPERATION DISPLAY
1. Press stop/cancel 3 times
Time of day or colon appears
in display
11:25
OPERATION DISPLAY
1. Press clock pad 3 times
DEMONSTRATION MODE
PRESS ANY KEY
OPERATION DISPLAY
1. Press clock pad 3 times
11:25
OPERATION DISPLAY
MIN SEC
625

7
3. SCHEMATIC DIAGRAM

8
12
WH
BR
BR
(W)
WIRING DIAGRAM
NOTE: *When replacing, check the lead colour as shown.
*Colours shown by ( ) indicate colours of leadwire connector housing.
MAGNETRON
HIGH VOLTAGE
INVERTER
SYMBOL COLOUR
OR ORANGE
BL BLUE
BR BROWN
W WHITE
Y YELLOW
RRED
GR GREY
BK BLACK
PRIMARY
LATCH SWITCH
TOP
SECONDARY
LATCH SWITCH
BOTTOM (OUTSIDE) SHORT SWITCH
BOTTOM (INSIDE)
POWER RELAY B
(RY1)
CAUTION:
HEAT SINK
(HOT/LIVE)
VERY HIGH
VOLTAGE &
TEMPERATURE

9
4. DESCRIPTION OF OPERATING SEQUENCE
4.1 Variable power cooking control
HIGH VOLTAGE INVERTER POWER SUPPLY (U) controls
output power by a signal from Digital Programmer Circuit (DPC).
Power relay 1 stays on to supply power to the inverter circuit.
The outpower is controlled by the drive signal level from the
inverter circuit.
NOTE 1: 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.
NOTE 2: If microwave cooking is over 8 minutes with HIGH
power, fan motor rotates for 1 minute after cooking to cool
oven and electric components.
4.2 Autoweight defrost, autoweight cook
When those auto control feature is selected and Start pad is
pressed:
1. The digital programmer circuit determines the power level
and cooking time to complete cooking and indicates the
operating state in the display. The table shows the
corresponding cooking times for respective weight by
categories.
2. When cooking time in the display window has elapsed, the
oven turns off automatically by the controlled signal from the
digital programmer circuit.
NOTE: After one touch menu and auto reheat cooking, fan
motor rotates for 1 minute to cool oven and electric
components.
VARIABLE POWER COOKING
AUTOWEIGHT DEFROST
AUTOWEIGHT COOK
POWER
SETTING OUTPUT POWER
APPROX.
RY-1 INVERTER
CONTROL
SIGNAL
HIGH 900W stay ON stay ON
DEFROST 270W stay ON ON/OFF
MEDIUM 600W stay ON stay ON
LOW 440W stay ON stay ON
SIMMER 250W stay ON ON/OFF
WARM 100W stay ON ON/OFF
CATEGORY WEIGHT COOKING TIME
BREAD 100g 50 seconds
MEAT ITEMS 150g 2 mins 21 Secs
MEAT JOINTS 400g 7 mins
CATEGORY WEIGHT COOKING TIME
CHILLED MEAL 200g 2 mins 50 secs
FROZEN MEAL 200g 6 mins 50 secs
JACKET POTATOES 150g 3 mins 22 secs

10
5. CAUTIONS TO BE OBSERVED WHEN TROUBLESHOOTING
Unlike many other appliances, the microwave oven is high-
voltage, high-current equipment. Though it is free from danger in
ordinary use, extreme care should be taken during repair.
5.1 Check the grounding
Do not operate on a 2-wire extension cord. The microwave oven
is designed to be used when grounded. It is imperative,
therefore, to make sure it is grounded properly before beginning
repair work.
5.2 Inverter Warnings
CAUTION
Servicemen should remove their watches whenever working
close to or replacing the magnetron.
DANGER OF HIGH VOLTAGE AND HIGH TEMPERATURE
(HOT/LINE) OF THE INVERTER POWER SUPPLY (U)
This High Voltage Inverter Power Supply circuit handles 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 by its high current and high voltages.
The aluminium heat sink is also energized with high voltage
(HOT), so do not touch when AC input terminal is connected to
the power devices (Collector) is directly connected to the
Aluminium heat sink.
The Aluminium heat sink may be HOT by 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.
NEW H.V.
HIGH VOLTAGE REMAINS IN
HIGH VOLTAGE CAPACITORS
DANGER OF HIGH VOLTAGE AND HIGH
TEMPERATURE (HOT/LIVE) OF HEAT SINK
HEAT SINK
CHOKE COIL
SAND BAR
RESISTOR
CUSTOM I.C.
CN 701
CURRENT
TRANSFORMER CN 703
SECONDARY
WINDINGS
DIODE
HIGH VOLTAGE
PRIMARY
WINDINGS
HIGH VOLTAGE
TRANSFORMER
FILM
CAPACITORS
PHOTO
COUPLER
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.
WARNING
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 oven energized. DO NOT
measure the voltage in the high voltage circuit including
filament voltage of magnetron.
WARNING
Never touch any circuit wiring with your hand nor with an
insulated tool during operation.
H.V. INVERTER(U)
BE SURE TO HAVE PROPER
GROUNDING PLATE
GROUNDING
MAGNETRON FILAMENT
INSULATED HANDLE
Touch chassis side first then short to the
terminal of the magnetron filament terminal
SCREWDRIVER
TERMINAL