Panasonic NN-A890WB User manual

Order Number MOP00100021C2
Microwave Oven
NN-A890WB / NN-A860WB
SPG Scandinavian Countries
WPG Switzerland
SPECIFICATIONS
1

2

2000 Matsushita ElectricIndustrial Co., Ltd. All rights reserved.
Unauthorized copying and distribution isaviolation of law.
3

1. Inverter Warning
The inverterboardlooks like a regularPCB, however, this PCB drives the magnetron tube using
veryhigh voltages and current.
It has
1. Veryhigh voltage and high current
2. AnAluminium heat sink that becomes veryhot
3. The capacitors on the inverter circuitwill containahigh voltage
charge even when the oven isnot operating.
Donot
1. Donot touch the circuitryas itcontains veryhigh voltages. When
replacing the board please take extreme care to avoidpossible
electricshock. High voltages mayremaininthe circuit.
2. Donot touch the aluminium heat sink as itwill become veryhot. It
also contains high voltages.
3. Donot attempt to repairthe inverter PCB as thiscan be very
dangerous. Replace the high voltage inverter circuitas acomplete
unit. Return the oldunitfullyrepacked inthe original shipping
box and completed paper work.
4. Donot adjust or tamper with the preset volume on the inverter
board. Itisverydangerous to adjust thispreset without proper
test equipment.
5. Donot test the oven whilethe inverter grounding stripor screws
are loose. Itisverydangerous to operate the inverter circuitboard
without aproper ground connection.
Figure 1
4

InverterGounding
Figure 2
InverterPCB layout
2. Feature Chart
5

Function NN-A890WB
SPG/WPG NN-A860WB SPG/WPG
Microwave 6 6
Grill 3 3
Convection 17 17
Combination YES YES
SensorReheat 2 -
SensorCook 6 -
SensorCombination 1 -
SensorCrisp 1 -
Weight Defrost 2 2
Weight Combination 6 6
Weight Reheat - 2
Weight Cook - 6
MemoryCook 1 1
Weight Crisp - 2
Stage Cooking 3 3
Delay/Stand YES YES
More/Less YES NO
Clock 24H 24H
Function NN-A890WB
SPG/WPG NN-A860WB SPG/WPG
WordPrompt * *
StepbyStep LED NONE
*None, Danish, English
3. Control Panel
4. Operation And Digital Programmer Circuit Test
Procedure
4.1. Word Prompting
4.2. Setting the Clock
6

4.3. Microwave Cooking
4.4. Auto Weight Defrost
4.5. DelayStand
7

4.6. DelayStart
4.7. ChildLock
4.8. Grill Operation
4.9. Convection Operation
8

4.10. Turbo Bake Operation
4.11. Combination Cooking (Convection and Microwave)
4.12. Combination Cooking (Grill and Microwave)
9

4.13. Combination Cooking (Turbo Bake and Microwave)
4.14. Memory
10

4.15. Auto Weight Cook Programs (NN-A860WB)
4.16. Auto Weight Cook Program (NN-A890WB)
4.17. Auto Sensor and Sensor Combi Programs (NN-A890WB)
5. Schematic Diagram
11

6. Wiring Diagram
7. Description of Operating instruction
7.1. Variablepower cooking control
The HIGH VOLTAGE INVERTER POWER SUPPLY controls the output powerbya signal fromthe
digital Programmercircuit DPC. The powerrelay(RY1) turns on tosupplypowertothe inverter
circuit. The level of output poweris controlledbythe drive signal level fromthe invertercircuit.
NOTE1: The ON/OFF time ratiodoes not correspond withthe percentage of microwave power
since approximately2 seconds are requiredforheating the magnetron filament. / NOTE: 2 If
microwave cooking is over8 minutes on HIGH power, the fanmotorrotates for1 minute after
cooking tocool the ovenand electrical components.
Dutycycles formicrowave cooking
Output DutyON/OFF
ON time OFF time
High 1000W 22” 0”
Defrost 440W 16” 6”
Medium 600W 22” 0”
Low 440W 22” 0”
Simmer 440W 15” 7”
Warm 440W 8” 14”
7.2. Grill Cooking
The digital programmercircuit controls the grill powerbyoperating the powerrelayRY4 inthe
sequence showninthe table below
Dutycycles forGrill Cooking
12

DutyON/OFF
ON Time OFF Time
Grill 1 66” 0”
Grill 2 54” 12”
Grill 3 42” 24”
7.3. Auto weight defrost, Auto weight Cook
Whenanautocontrol feature is selectedand the start padpressed:
1. The digital programmer circuitdetermines the power level and the
cooking time and indicates the operating state inthe display. The
tableshowsthe corresponding cooking times for each category
and its respective weight.
2. When the cooking time inthe displaywindow has elapsed, the
oven turns off automaticallyviathe control signal from the digital
programmer circuit.
Note: After auto cooking ifthe oven temperature isover the
predetermined temperature the fan motor rotates to cool the oven
and its components.
AutoWeight Defrost NN-A890WB
Category 1st Touch
Weight Cooking Time
1.Reheat 300 4m
2.FrozenReheat 300 8m
Autoweight Cook NN-A890WB
Category 1st Touch
Weight Cooking Time
11.Roast Pork 1000 33m20s
12.Roast Beef 700 16m25s
13.Poultry 500 17m10s
14.FrozenChicken
Pieces 500 22m50s
15.Pasta Gratin 1000 21m20s
16.FrozenBreadand
Rolls 50 6m
Autoweight Cook NN-A860WB
13

Category 1st Touch
Weight Cooking Time
3.FreshVegatables 500 8m40s
4.Root Vegetables 500 9m30s
5.Potatoes 500 9m
6.Fish 500 7m
7.Rice 200 7m32s
8.Rice Pudding 600 32m20s
9.Roast Pork 1000 33m20s
10.Roast Beef 700 16m25s
11.Poultry 500 17m10s
12.FrozenChicken
Pieces 500 22m50s
13.Pasta Gratin 1000 21m22s
14.PotatoGratin 1000 22m50s
15.FrozenPizza 300 17m11s
16.FrozenBreadand
Rolls 50 6m
7.4. Convection Cooking
1. The digital programmer circuitoperates the power relaysRY3,RY5
and RY6 inthe sequence as showninthe figure below.
2. When the oven reaches apredetermined temperature the digital
programmer circuitstops supplying power to relayRY5, resulting
inthe convection heater turning off.
3. When the temperature drops below the predetermined
temperature, the digital programmer circuitsupplies power to
power relayRY5 resulting inthe convection heater turning on.
Note: After the convection process, ifthe oven temperature is
higher than the predetermined temperature, the fan motor rotates
to cool the electroniccomponents and the oven.
Figure 1
14

Convection Cooking DutyCycles
7.5. Combination Cooking
Combination cooking is achievedbyoperating the microwave and heatermodes together
during one cooking cycle. There are three combination modes.
1. Combination (convection and microwave)
2. Combination (grill and microwave)
3. Combination (grill, convection and microwave)
The digital programmercircuit operators the powerrelays as showninthe figures below.
Whenthe oventemperature reaches the predeterminedtemperature, the digital programmer
circuit stops supplying powertorelay(RY5) resulting inthe convection heaterturning off.
During this time the digital programmercircuit continues tooperate relay(RY1) sothat
microwave activitycontinues at the dutycycle selected. The invertercontrol signal level is also
maintained. The microwave activitycontinues tocycle until the entire cooking programis
completed.
Whenthe oventemperature drops belowthe selectedtemperature, the digital programmer
circuit operates powerrelay(RY5) switching on the heaterelements.
Inthe case of grill combination the sequence applies withthe digital programmercircuit
switching powerrelay(RY4) tocontrol, the grill elements.
Withconvection, grill and micropowercombination. The grill elements and convection
elements are operatedalternativelywhilst the oventemperature is above the selectedlevel.
Convection And Microwave Combination DutyCycles
Convection Heater Micropower
100 - 250 C OUTPUT ON OFF
440W 360W 66 0
250W 360W 48 18
100W 360W 21 45
15

Grill And Microwave Combination DutyCycles
Grill Heater Micropower
ON OFF OUTPUT ON OFF
Grill 1 51 15
Grill 2 42 24 440W 360W 66 0
Grill 3 26 38 250W 360W 48 18
100W 360W 21 45
Grill Convection And Microwave Combination DutyCycles
Convection
Heater Grill Heater Micropower
100 - 250 C ON OFF OUTPUTON OFF
Grill
151 15
Grill
242 24 440W 360W 66 0
Grill
328 38 250W 360W 48 18
100W 360W 21 45
Figure 1
Convection and microwave dutycycles
Figure 2
Grill and microwave dutycycles
16

Grill,Convection and microwave dutycycles
7.6. One touch Auto sensor cooking NN-A890WB
Autosensorcook is a revolutionarywaytocook bymicrowave without setting a powerlevel or
selecting a time. All that is necessaryis toselect anautosensorprogrambefore starting to
cook. /
Understanding Autosensorcooking / / As food cooks, a certainamount of steamis produced.
If the food is covered, this steambuilds up and eventuallyescapes fromthe container. Inauto
sensorcooking, a carefullydesignedinstrument, calledthe humiditysensorelement, senses
the escape of steam. then, basedupon the autosensorprogramselected, the unit will
automaticallydetermine the correct powerlevel and the properlengthof time it will take tocook
the food.
NOTE: Autosensorcooking is successful withthe foods and recipes found inthe autosensor
cooking guide. Because of the vast differences infood composition, items not mentionedinthe
cooking guide shouldbe preparedinthe microwave ovenusing the powerselect and time
features. Please consult variable powermicrowave cook book forprocedures.
/ Explanation of the autosensorcooking process /
1. The shaded columns infigure 1indicate when the humidity
sensor heater ison.
2. During the 30 second period there isno microwave activity. When
calculating the T2 time byusing the formulabelow, make sure this
30 seconds issubtracted from the T0 time.
3. T1 time T0 time -30 seconds
4. T2 time when the steam escapes from the cooking container
placed inthe oven, the humiditysensor detects itand the
microprocessor calculates the balance of cooking time. ThisT2
17

time isthen showninthe displayand begins counting down.
Balance of cooking (T2 time)
The balance of cooking time whichis calledT2 time, canbe calculatedbythe following formula.
/ T2 time (insec.) = T1 time x K factor
NOTE: Remember, the T1 time starts afterthe start padis tapped. The coefficient K is
programmedintothe microprocessormemoryand theyare listedinthe following tables along
withthe P1 and P2 powe r. /
NOTE: When“More“or“Less” padis selected, the K factorvaries resulting inT2 time tobe
increasedordecreased.
Calculating the T2 time
Example 1: If the t1 time is measuredtobe 2 minutes and 40 seconds, and the autosensor
programis selectedis sensorreheat. Fish(Program6)
T2 = T1 x K
= 2 min. and 40 sec. X. 0.3
= 48 sec.
Category P1 POWER P2 POWER K FACTOR
STANDARD
1. Frozen
reheat HIGH HIGH 0.3
2. Reheat MED HIGH 0.4
Figure 1
Autosensorcooking
8. Cautions to Be Observed When Troubleshooting
Unlike manyotherappliances, the microwave ovenis a high voltage, high current is device.
Though it is free fromdangerinordinaryuse, extreme care shouldbe takenduring repair.
Caution
Servicemen shouldremove theirwatches whenever working close
to or replacing the magnetron.
8.1. Check the grounding
Donot operate on a twowire extension cord. The microwave ovenis designedtobe usedwhen
18

grounded. It is imperative, therefore, toensure the appliance is properlygroundedbefore
beginning repairwork.
8.2. Inverter Warnings
DANGER, HIGH VOLTAGE AND HIGH TEMPERATURE (HOT/LINE) OFTHE INVERTER POWER
SUPPLY (U)
Thishigh voltage inverter power supplyhandles veryhigh voltage
and veryhigh current for the magnetron tube. Though itisfree from
danger inordinaryuse, extreme care shouldbe taken during repair.
Asyou can see, itlooks like aTV flyback transformer, however, the
current isextremelylarge and istherefore, dangerous due to this
high current and high voltage.
The aluminium heat sink isalso energized with high voltage (HOT),
so do not touch when the AC input terminal isconnected. The
power devices (Collector) isdirectlyconnected to the aluminium
heat sink.
The aluminium heat sink maybe (HOT) due to heat energy,
therefore, extreme care shouldbe taken during servicing.
Figure 1
HV Inverterwarning
WARNING FOR INVERTER POWER SUPPLY (U) GROUNDING
Check the high voltage inverter power supplycircuitgrounding.
Thishigh voltage inverter power supplycircuitboard must have a
proper chassisground, the inverter grounding bracket must be
connected to the chassis. Ifthe inverter board isnot grounded it
will expose veryhigh voltages and cause extreme DANGER!Be
sure that the inverter circuitisproperlygrounded viathe inverter
earth bracket. Figure 2
19

InverterGrounding
WARNING!DISCHARGE THE HIGH VOLTAGE CAPACITORS
For about 30 seconds after the oven isturned off, an electriccharge
remains inthe high voltage capacitors inthe inverter power supply
circuitboard.
When replacing or checking parts, remove the power plug from the
outlet and short the inverter output terminal of the magnetron
filament terminalsto the chassisground with an insulated handle
screwdriver to discharge. Please be sure to touch the chassis
ground side first and then short to the output terminals.
Figure 3
Discharging the high voltage capacitors
WARNING
There ishigh voltage present with high current capabilities inthe
circuits of the primaryand secondarywindings, choke coil and heat
sink of the inverter. Itisextremelydangerous to work on or near
these circuits with the oven energized. DO NOTmeasure the
20