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4. DESCRIPTION OF OPERATING SEQUENCE

4.1 Variable power cooking control

The coil of power relay B(RY 1) is energized intermittently
by the digital programmer circuit, when the oven is set at
any power selection except for high power position. the digi-
tal programmer circuit controls the ON-OFF time of power
relay B contacts in order to vary the output power of the
microwave oven from “Warm” to “High” power. One com-
plete ON and OFF cycle of power relay B is 29 seconds.
The relation between indications on the control panel and
the output of the microwave oven is as shown in the table.

NOTE: The ON/OFF time ratio does not correspond with

the percentage of microwave power since
approximately 2 seconds are required for heat-
ing of magnetron filament.

4.2 Cyclic defrost

When defrost power and defrosting time is selected and
start pad is touched:
1. The digital programmer circuit (DPC) divides the total

defrosting time into 5 periods, consisting of 3 defrosting
periods, each followed by a standing period except last
defrosting.

2. During 1st defrosting power periods, power relay B ener-

gized for 17 seconds and de-energized for 12 seconds by
DPC.

3. During 2ND and LAST defrosting power periods, power

relay B energized for 14 seconds and de-energized for
15 seconds by DPC.

4. During standing periods, power relay B energized for 5

seconds and de-energized for 24 seconds by DPC.

NOTE: Defrosting time selected is converted into cer-

tain percent by the DPC but the display will
show selected time in minutes and seconds as
programmed. The total number of seconds is
divided into 5 different periods.

Example #2: If Defrosting time is selected for 10 minutes,
each operationg period will be as follows:

10minutes = 600seconds, 600/100 = 6seconds(1%)

4.3 Auto defrost, auto reheat cook control

When the auto control feature is selected and start pad is
touched:
1. The digital programmer circuit determines the power level

and cooking time to complete cooking and indicates the
operating state in the display window. The table shows
the corresponding cooking times for respective serving
by categories.

2. When cooking time in the display window has elapsed,

the oven turns off automatically by a control signal from
the digital programmer circuit.

AUTO DEFROST

AUTO REHEAT

POWER

SETTING

HIGH

LOW

WARM

CYCLIC

DEFROST

OUTPUT

POWER

APPROX.

800W
470W
140W
250W

ON TIME OF

POWER RELAY B

ON(SEC)

29
17

5

OFF TIME OF

POWER RELAY B

OFF(SEC)

0

12
24

Please refer to

description of cyclic defrost

CATEGORY

1.BREAD
2. MEAT

WEIGHT

80g

180g

TOTAL

DEFROSTING

TIME

0m 40s
3m 54s

CATEGORY

1. REHEAT
2. JACKET POTATO
3. FROZEN VEG.

WEIGHT

300g
400g
500g

COOKING TIME

4m 00s
8m 00s

10m 00s

20%

(120sec.)

(2min.)

20%

(120sec.)

(2min.)

10%

(60sec.)

(1min.)

40%

(240sec.)

(4min.)

10%

(60sec.)

(1min.)

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Summary of Contents for NN-E251W

Page 1: ...L Outside Dimensions 465mm W X 346mm D X 279mm H Inside Dimensions 290mm W X 306mm D X 220mm H Weight 12 5 kg Specifications subject to change without notice Specifications 2001 Matsushita Electric Industrial Co Ltd All rights reserved Unauthorized copying and distribution is a violation of law Order number MOP0105003C2 Microwave Oven NN E251W Service Manual ...

Page 2: ...ed 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 dan gers 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 the service informatio...

Page 3: ...our instructions During cooking one press temporarily stops the cooking program Another press can cels all your instructions and the time of day will appear in the display 10 start pad BEEP SOUND When a pad is touched correctly a beep will be heard If a pad is touched and no beep is heard the unit has not or cannot accept the instruction At the end of any complete program the oven will beep 5 time...

Page 4: ...times Press twice Press Clock pad Press Time pads Press Clock pad Display will show 12H Enter time of day by pressing appropriate time pads Numbers stop blinking When you press any number pads numbers will start blinking Press the pad with the power Select cooking time by pressing Press Start you require appropriate pads The cooking program will start and the time in the display will count down Pr...

Page 5: ...econds by DPC 4 During standing periods power relay B energized for 5 seconds and de energized for 24 seconds by DPC NOTE Defrosting time selected is converted into cer tain percent by the DPC but the display will show selected time in minutes and seconds as programmed The total number of seconds is divided into 5 different periods Example 2 If Defrosting time is selected for 10 minutes each opera...

Page 6: ... 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 other holes or gaps because such objects may work as an antenna and cause microwave leakage 5 7 5 8 CAUTION Servicemen should remove their watches whenever working close to or replacing the magnetron WARNING Never operate the ...

Page 7: ... the escutcheon base with double sided adhesive tape Therefore applying hot air e g using a hair dryer is recommended for smoother removal NOTE 2 When installing new membrane keyboard make sure that the surface of the escutcheon base is cleaned sufficiently so that any problems shorted contacts or uneven surface can be avoided NOTE 3 Alignment position of membrane keyboard and escutcheon sheet are...

Page 8: ...and adjustment so as to prevent an excessive microwave leakage 1 When mounting the door to the oven be sure to adjust the door parallel to the bottom line of the oven face plate by moving the upper hinge and lower hinge in the direc tion necessary for porper alignment 2 Adjust so that the door has no play between the inner door surface and oven front surface If the door assembly is not mounted pro...

Page 9: ...uity check between each filament terminal and magnetron case should read open 7 4 Diode 1 Isolate the diode from the circuit by disconnecting the leads 2 With the ohmmeter set the highest resistance scale measure the resistance across the diode terminals Reverse the meter leads and again observe the resis tance reading Meter with 6V 9V or higher voltage batteries should be used to check the front ...

Page 10: ...l protector exceeds its temperature it will turn off the power to oven cavity and display will go to reset mode The cooking program can be reset after cool down 7 7 HV Fuse 1 Isolate the HV Fuse assembly from the circuit by discon necting its leads 2 With the ohmmeter set at the highest resistance scale measure the resistance across the HV fuse terminals A normal HV fuse resistance will be 0Ω It i...

Page 11: ...rocedures it is recommended to test the magnetron using the simple method outlined below Necessary equipment 1 Iitre beaker Glass thermometer Wrist watch or stopwatch NOTE Check the line voltage under load to ensure it meets specifications Low voltage will cause reduction in the magnetron output Temperature readings and heating time should be as accurate as possible Output power performance test p...

Page 12: ...d Fuse is OK No display and no operation at all 2 Oven does not accept key input program 3 Oven lamp and turntable motor turn on when oven is plugged in with door closed 4 Timer starts countdown but no microwave oscillation 1 Open or loose lead wire harness 2 Open oven thermostat 3 Open low voltage transformer 4 Defective DPC 1 Key input is not in sequence 2 Open or loose connection of mem brane k...

Page 13: ...bles SYMPTOMS CAUSE CORRECTIONS 1 Microwave output is low Oven takes longer time to cook food 2 Turntable motor and oven lamp turn on when door is opened 3 Oven does not operate 4 Loud buzzing noise can be heard 5 Oven stops operation during cooking 6 Turntable motor does not rotate 1 Decrease in power source voltage 2 Open or loose wiring of magnetron filament circuit Intermittent oscilla tion 3 ...

Page 14: ...set and the start pad is tapped No microwave oscillation at 1 IC 1 pin 8 voltage while operation Abnormal IC 1 any power setting at high power Normal 5V RY1 Q10 D3 Dark or unclear display 1 Replace display and check operation Normal DISPLAY Abnormal IC 1 Missing or lighting of 1 Q1 Q7 check operation Normal Step 2 unnecessary segment Abnormal Q1 Q7 2 Replace IC 1 and check operation Normal IC 1 Ab...

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