Maytag Mmv4205aaw, Mmv4205aab, Mmv4205aaq, Mmv4205aas Service Manual

Microwave Oven Service Manual

MMV4205AAB MMV4205AAQ MMV4205AAS MMV4205AAW

CAUTION

BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.

CAUTION

WARNING TO SERVICE TECHNICIANS

PRECAUTIONS TO BE OBSERVED BEFORE AND

DURING SERVICING TO AVOID POSSIBLE EXPOSURE

TO EXCESSIVE MICROWAVE ENERGY

a. Do not operate or allow the oven to be operated with the door open.

b. Make the following safety checks on all ovens to be serviced before activating the

magnetron or other microwave source, and make repairs as necessary; (1) Interlock operation, (2) proper door closing, (3) seal and sealing surfaces (arcing, wear, and other damage), (4) damage to or loosening of hinges and latches, (5) evidence of dropping or abuse.

c. Before turning on microwave power for any service test or inspection within the

microwave generating compartments, check the magnetron, wave guide or transmission line, and cavity for proper alignment, integrity, and connections.

d. Any defective or misadjusted components in the interlock, monitor, door seal, and

microwave generation and transmission systems shall be repaired, replaced, or adjusted by procedures described in this manual before the oven is released to the owner.

e. A Microwave leakage check to verify compliance with the Federal performance

standard should be performed on each oven prior to release to the owner.

• Proper operation of the microwave ovens requires that the magnetron be assembled to the wave guide and cavity.Never operate the magnetron unless it is properly installed.

• Be sure that the magnetron gasket is properly installed around the dome of the tube whenever installing the magnetron.

• Routine service safety procedures should be exercised at all times.

• Untrained personnel should not attempt service without a thorough review of the test procedures and safety information contained in this manual.

FOREWORD

Read this Manual carefully.Failure to adhere to or observe the information in this Manual may result in exposing yourself to the Microwave Energy normally contained within the oven cavity.

MODEL MMV4205AAB

MMV4205AAQ MMV4205AAS MMV4205AAW

TABLE OF CONTENTS

(Page)

SAFETY PRECAUTIONS ................................................................................................................Inside front page

SPECIFICATIONS................................................................................................................................................ 1-1

CAUTIONS ........................................................................................................................................................... 2-1

INSTALLATIONS.................................................................................................................................................. 3-1

OPERATING INSTRUCTIONS............................................................................................................................. 4-1

CONTROL PANEL ............................................................................................................................................... 4-1

CONTROL PANEL INSTRUCTIONS.................................................................................................................... 4-2

OVERALL CIRCUIT DIAGRAM............................................................................................................................ 5-1

SCHEMATIC DIAGRAM (I)................................................................................................................................... 5-1

SCHEMATIC DIAGRAM (II).................................................................................................................................. 5-2

MATRIX CIRCUIT FOR TOUCH KEY BOARD .................................................................................................... 5-3

GENERAL INFORMATION FOR SERVICE ......................................................................................................... 6-1

GENERAL PRECAUTIONS IN USE .................................................................................................................... 6-1

TRIAL OPERATION ............................................................................................................................................. 6-1

FEATURES AND SPECIFICATIONS FEATURES............................................................................................... 6-1

SERVICE INFORMATION.................................................................................................................................... 7-1

PRECAUTIONS AND REPAIR SERVICE TIPS ................................................................................................... 7-1

MICROWAVE LEAKAGE TEST ........................................................................................................................... 7-2

POWER OUTPUT MEASUREMENT.................................................................................................................... 7-3

DISASSEMBLY INSTRUCTIONS ........................................................................................................................ 7-4

INTERLOCK SYSTEM ....................................................................................................................................... 7-11

INTERLOCK CONTINUITY TEST ...................................................................................................................... 7-13

TEST AND CHECKOUT PROCEDURES AND TROUBLESHOOTING............................................................. 7-14

A.TEST PROCEDURES..................................................................................................................................... 7-14

B.CHECKOUT PROCEDURES.......................................................................................................................... 7-18

C.TROUBLESHOOTING .................................................................................................................................... 7-20

EXPLODED VIEW ................................................................................................................................................ 8-1

REPLACEMENT PARTS LIST ............................................................................................................................. 8-9

SPECIFICATIONS

Rated Power Consumption ................................1700W maximum

Microwave Output ...............................................1150W (IEC 60705)

Frequency ..........................................................2450 MHz ±50 MHz

Power Supply .....................................................120 VAC,60 Hz

Rated Current ....................................................14.5 Amp.(Microwave oven+Cook top lamps+Ventilation fan)

Magnetron Cooling .............................................Forced Air Cooling

Rectification .......................................................Rectification Voltage Double Half-Wave

Door Sealing ......................................................Choke System

Safety Devices ...................................................Magnetron Thermostat: Open at 150 °C ±5 °C

............................................................................Oven Thermostat: Open at 110 °C ±5 °C

............................................................................Fuse(20A)

............................................................................Primary Interlock Switch

............................................................................Secondary Interlock Switch

............................................................................Interlock Monitor Switch

Magnetron ..........................................................2M282J (Toshiba)

Cook top Lamp ...................................................125 V, 30 W or 40 W

Cavity Lamp .......................................................125 V, 30 W or 40 W

Timer ..................................................................Digital,up to 99 min.99 sec.(in each cooking stage)

Tray ....................................................................Tempered Safety Glass

Overall Dimensions ............................................2915/16”(W)x167/16”(H)x153/8”(D)

Oven Cavity Size ...............................................231/2”(W)x103/16”(H)x141/2”(D)

Effective Capacity of Oven Cavity ......................2.0 Cu.ft.

Accessories ........................................................Owner ’s Manual &Cooking Guide,Installation Manual,

............................................................................Exhaust Adapter, Exhaust Damper, Mounting Kit and Filter,

............................................................................Rotating Ring Assembly, Glass Tray, Metal Rack.

(Microwave oven+Cook top lamps+Ventilation fan)

Close at 0 °C ±5 °C

SWITCH CHART

PRIMARY

SWITCH MODE

CONDITIONS

DOOR OPEN DOOR CLOSED

NOTE: Use the above switch chart with circuit diagram on page 5-1.

INTERLOCK

SWITCH

COM

OPEN OPEN CLOSE

CLOSE CLOSE OPEN

1-1

SECONDARY

INTERLOCK

SWITCH

COM

INTERLOCK

MONITOR

SWITCH

COM

CAUTIONS

Unlike other appliances,the microwave oven is high-voltage and high-current equipment. Though it is free from danger in ordinary use, extreme care should be taken during repair.

• DO NOT operate on a 2-wire extension cord during repair

and use.

• NEVER TOUCH any oven components or wiring during

operation.

• BEFORE TOUCHING any parts of the oven,,always

remove the power plug from the outlet.

• Remove your watches whenever working close to or

replacing the Magnetron.

• DO NOT touch any parts of the control panel circuit. A

resulting static electric discharge may damage this P.C.B.

• NEVER operate the oven with no load..

• NEVER injure the door seal and front plate of the oven

cavity.

• NEVER put iron tools on the magnetron.

• NEVER put anything into the latch hole and the interlock

switches area.

MICROWAVE RADIATION

Personnel should not be exposed to the microwave energy which may radiate from the magnetron or other microwave generating device if it is improperly used or connection. All input and output microwave connections, waveguide,flange,and gasket must be secure never operate the device without a microwave energy absorbing load attached. Never look into an open waveguide or antenna while the device is energized.

• Proper operation of the microwave oven requires that the magnetron be assembled to the waveguide and cavity. Never operate the magnetron unless it is properly installed.

• Be sure that the magnetron gasket is properly installed around the dome of the tube whenever installing the magnetron.

ANTENNA

COOLING FIN

MAGNETRON CHASSIS GROUND

Gasket

FILAMENT TERMINALS

MAGNETRON

THE OVEN IS TO BE SERVICED ONLY BY PROPERLY QUALIFIED SERVICE PERSONNEL.

2-1

INSTALLATIONS

Plug with Ground Prong

Properly Polarized and Grounded Outlet

BEFORE YOU BEGIN, READ THE FOLLOWING INSTRUCTIONS COMPLETELY AND CAREFULLY.

PRECAUTIONS ON INSTALLATION

A. Plug the power supply cord into a 120V AC,60Hz,

single-phase power source with a capacity of at least 20 amperes.

B. Avoid placing the unit in a location where there is

direct heat or splashing water. C. Install the unit on the mounting plate firmly. D. Place the unit as far away as possible from TV,

radio,etc.to prevent interference.

GROUNDING INSTRUCTIONS

For personal safety,this appliance must be fully grounded at all times.

In the event of an electrical short circuit,grounding reduces the risk of electrical shock. The plug must be plugged into an outlet that is properly installed and grounded.

CAUTION

This unit is equipped with a 3-prong plug for your safety.If the wall outlet is a grounded 3-hole type, the unit will be grounded automatically.

WARNING

Improper use of the grounding plug can result in a risk of electric shock. Do not,under any circumstances,cut or remove the third ground prong from the power cord plug.

3-1

CONTROL PANEL

OPERATING INSTRUCTIONS

4-1

CONTROL PANEL INSTRUCTIONS

1. DISPLAY: The Display includes a clock and indicators

to tell you time of day, cooking time setting and cooking functions selected.

2. POPCORN: Touch this pad when popping popcorn in

your microwave oven.

3. BAKED POTATO: Touch this pad to cook potatoes.

4. BEVERAGE: Touch this pad to reheat one or two

cups of a bev-erage.

5. COOK: Touch this pad to cook Fresh Vegetable,

Frozen Vegetable, Casserole, Rice, Oatmeal, Bacon, Scrambled Eggs, and Frozen Entrée.

6. REHEAT: Touch this pad to reheat Pizza Slice, Dinner

Plate, Soup/Sauce, Casserole, and Roll/ Muffin.

7. POULTRY: Touch this pad to cook chicken wings,

chicken nuggets, Spicy Chicken and Mexican Chicken.

8. SOFTEN: Touch this pad to soften Butter, Ice Cream,

Cream Cheese and Frozen Juice.

9. MELT: Touch this pad to melt Butter/Margarine,

Chocolate, Cheese and Marshmallows.

10. AUTO DEFROST: Meat, poultry, fish and bread.

Touch this pad to select food type and defrost food by weight.

11. TIME DEFROST: Touch this pad to defrost most other

frozen foods.

12. RAPID DEFROST: This pad provides RAPID defrost

for 1.0 pound of frozen food.

13. NUMBER: Touch number pads to enter cooking time,

power level, quantities, or weights.

16. ADD 30 SEC.: Touch this pad to

set and start quickly at 100% power level.

17. CUSTOM PROGRAM: Touch this pad to recall one

cooking instruction previously programmed into memory.

18. POWER LEVEL: Touch this pad to select a cooking

power level.

19. COOK TIME: Touch this pad to to set a cooking time.

20. STOP/CLEAR: Touch this pad to stop the oven or to

clear all entries.

21. CONTROL SETUP: Touch this pad to change the

oven’s default settings for sound, clock, display speed and defrost weight.

22. ENTER/START: Touch this pad to start a function. If

you open the door after oven begins to cook, touch ENTER/START again.

23. KITCHEN TIMER: Touch this pad to set the kitchen

timer.

24. TURNTABLE ON/OFF: Touch this pad to turn off the

turntable. OFF will appear in the display.

25. LIGHT TIMER: Touch this pad to set the light timer.

26. VENT HI/LO/OFF: Touch this pad to turn the fan on or

off.

27. VENT AUTO TIME SET: Touch this pad when setting

ventilation time. (1, 3, 5, 10, 30 minutes.)

28. LIGHT HI/LO/OFF: Touch this pad to turn on the

cooktop/countertop light.

14. CLOCK: Touch this pad to enter the time of day.

15. HOLD WARM: Touch this pad to keep hot, cooked

foods warm in your microwave oven for up to 90 minutes.

4-2

OVERALL CIRCUIT DIAGRAM

SCHEMATIC DIAGRAM (I) *Check the Model No.

5-1

SCHEMATIC DIAGRAM (II) *Check the Model No. (ADD Noise filter)

5-2

MATRIX CIRCUIT FOR TOUCH KEY BOARD

5 6 7

KEY MATRIX

5-3

GENERAL INFORMATION FOR SERVICE

GENERAL PRECAUTIONS IN USE

A. Never operate the unit when it is empty.

Operating the oven with no load may shorten the

life of the magnetron.Whenever cooking dry foods

(dried fish,bread,etc.)or a small amount of food,

be sure to put a glass of water into the cooking

compartment.The glass turntable may become hot

after operating,be careful when touching it. B. Aluminum foil should be avoided because it will

disrupt cooking and may cause arcing.However,

small pieces may be used to cover some parts of

food to slow the cooking.Any aluminum foil used

should never be closer than 2.5 cm to any side wall

of the oven.

TRIAL OPERATION

After installation,the following sequences and results should be checked carefully.

A. Put a container filled with water (about 1 liter)into

the oven,and close the door tightly. B. Set cooking time for 10 minutes by touching “1 ”

and then “0 ” three times.“1,0,0,0 ” appears in the

display window. C. Touch the START key.

Make sure the cavity light comes on.The unit will

begin cooking and the display window will show the

time counting down by seconds. D. After about 5 minutes,make sure the primary

interlock switch,the secondary interlock switch and

the interlock monitor switch operate properly by

opening and closing the door several times.Touch

the START key each time the door is closed. E. Continue operating the unit.Two short and a long

beep sound signal is heard when the time is up.

The unit will shut off automatically. F. Confirm the water is hot. G. Finally,measure the output power according to

“POWER OUTPUT MEASUREMENT ” on page 7-3.

FEATURES AND SPECIFICATIONS FEATURES

A. The safety systems incorporated in this model are:

(1) Primary interlock switch (2) Secondary interlock switch (3) Interlock monitor switch (4) Choke system (5) Oven cavity thermostat

(Note This thermostat located on the oven cavity will open and stop the unit from operation only if a high temperature is reached,such as, a fire created by overcooking food.)

B. Any one of 10 power output levels ranging 0W to

1100W can be selected by the touch control and electronic computer system.

C. Cooking time can be displayed on the digital

readout.

D. Three different cooking stages (Include Defrost)

can be changes from one cooking stage to another. This is made possible with the memory function of the microprocessor.

6-1

SERVICE INFORMATION

PRECAUTIONS AND REPAIR SERVICE TIPS

PRELIMINARY

A. SINCE NEARLY 4000 VOLTS EXISTS IN SOME

CIRCUITS OF THIS UNIT REPAIRS SHOULD BE

CARRIED OUT WITH GREAT CARE.

The filament leads of magnetron carry High

Voltage with respect to ground.Extreme caution

must be exercised.Never plug the unit into a

power source to determine which component is

defective in high voltage section.

B. TO AVOID POSSIBLE EXPOSURE TO

MICROWAVE ENERGY LEAKAGE, THE

FOLLOWING PRECAUTIONS MUST BE TAKEN

BEFORE SERVICING.

(1) Before the power is applied:

(a) Make sure the primary interlock switch,the

secondary interlock switch and the interlock monitor switch operate properly by opening and closing the door several by opening and closing the door several times.

(b) Make sure the perforated screen and the

dielectric choke of the door are correctly and firmly mounted.

(2) After power is applied:

(a) Make sure the interlock switch mechanism

is operating properly by opening and closing the door.

(b)

Check microwave energy leakage must be below the limit of 5 mW/cm2. (All service adjustments should be made for minimum microwave energy leakage readings).

(3) Do not operate the unit until it is completely

repaired,if any of the following conditions exist.

The unit must not be operated. (a) The door does not close firmly. (b) The hinge is broken. (c) The door seal is damaged. (d) The door is bent or warped,or there is any

other visible damage on the unit that may cause microwave energy leakage.

NOTE: Always keep the seal clean. (e) Make sure that there are no defective parts

in the interlock mechanism.

(f) Make sure that there are no detective parts

in the microwave generating and transmission assembly (especially waveguide).

(4) The following items should be checked after the

unit is repaired: (a) The interlock monitor switch is connected

correctly and firmly.

(b) The magnetron gasket is properly positioned

and mounted.

(no microwave energy leakage)

(d) The door can be properly closed and the

safety switches work properly.

(e) The unit must stop when the door is opened or

the time is up.

The unit must not be operated with any of the above components removed or by-passed.

7-1

MICROWAVE LEAKAGE TEST

CAUTIONS

• Be sure to check microwave leakage prior to servicing the oven if the oven is operative prior to servicing.

• The service personnel should inform the manufacture importer, or assembler of any certified oven unit found to have a microwave emission level in excess of 5 mW/cm2and should repair any unit

found to have excessive emission levels at no cost to the owner and should ascertain the cause of the excessive leakage.The service personnel should instruct the owner not to use the unit until the oven has been brought into compliance.

• If the oven operates with the door open,the service personnel should;

- Tell the user not to operate the oven

- Contact the manufacturer and CDRH (Center for Devices and Radiological Health)immediately. NOTE: Address on CDRH

Office of Compliance (HFZ-312) Center for Devices and Radiological Health 1390 Piccard Drive Rockville,Maryland 20850

• The service personnel should check all surface and vent openings for microwave emission testing.

• Check for microwave energy leakage after every servicing.The power density of the microwave radiation leakage emitted by the microwave oven should not exceed 1mW/cm.sq.And always start measuring of an unknown field to assure safety for operating personnel from radiation leakage. NOTE: The standard is 5mW/cm.sq.while in the customer ’s home.1mW/cm.sq.stated here is manufacturer ’s own voluntary standard for units in customer ’s home.

EQUIPMENT-

• TESTER ((VOLTS-DC,AC,Ohmmeter)

• Microwave survey meter

- Holaday HI-1500 HI-1501

- Narda 8100

8200

• 600 cc non conductive material beaker ((glass or plastic),inside diameter:approx.8.5 cm (3 1 /2 in.)

• Glass thermometer::100 °C or 212 °F (1 deg scale)

MEASURING MICROWAVE ENERGY LEAKAGE

• Pour 275±15cc of 20±5°C(68±9°F) water in a beaker which is graduated to 600 cc, and place the beaker on the oven.

• Set the energy leakage monitor to 2,450 MHz and use it following the manufacturer's recommended test procedure to assure correct result.

• When measuring the leakage, always use the 2-inch (5cm) spacer supplied with the probe.

• Operate the oven at its maximum output.

• Measure the microwave radiation using and electromagnetic radiation monitor by holding the probe perpendicular to the surface being measured.

Move probe along shaded area.

Probe scanning speed Less than 2.5 cm/sec. ( 1 in/sec)

7-2

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