SAMSUNG MW7491GXAA Service Manual

MICROWAVE OVEN

MW7491G

SERVICE

Manual

MICROWAVE OVEN

CONTENTS

1. Precaution

2. Specifications

3. Operating Instructions

4. Disassembly and Reassembly

5. Alignment and Adjustments

6. Troubleshooting

7. Exploded Views and Parts List

8. PCB Diagrams

9. Schematic Diagrams

SEA

Samsung Electronics

(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.

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.

PRECAUTIONS TO BE OBSERVED BEFORE AND DURING SERVICING TO AVOID POSSIBLE EXPOSURE TO EXCESSIVE MICROWAVE ENERGY

1. Precaution

1-1 Safety precautions ( )

Samsung Electronics 1-1

Follow these special safety precautions. Although the microwave oven is completely safe during ordinary use, repair work can be extremely hazardous due to possible exposure to microwave radiation, as well as potentially lethal high voltages and currents.

1. All repairs should be done in accordance with the procedures described in this manual. This product complies with Federal Performance Standard 21 CFR Subchapter J (DHHS).

2. Microwave emission check should be performed to prior to servicing if the oven is operative.

3. If the oven operates with the door open : Instruct the user not to operate the oven and contact the manufacturer and the center for devices and radiological health immediatly.

4. Notify the Central Service Center if the microwave leakage exceeds 5 mW/cm

5. Check all grounds.

6. Do not power the MWO from a "2-prong" AC cord. Be sure that all of the built-in protective devices are replaced. Restore any missing protective shields.

7. When reinstalling the chassis and its assemblies, be sure to restore all protective devices, including: nonmetallic control knobs and compartment covers.

8. Make sure that there are no cabinet openings through which people--particularly children--might insert objects and contact dangerous voltages. Examples: Lamp hole, ventilation slots.

9. Inform the manufacturer of any oven found to have emmission in excess of 5 mW/cm2, Make repairs to bring the unit into compliance at no cost to owner and try to determine cause. Instruct owner not to use oven until it has been brought into compliance.

CENTRAL SERVICE CENTER

10. Service technicians should remove their watches while repairing an MWO.

11. To avoid any possible radiation hazard, replace parts in accordance with the wiring diagram. Also, use only the exact replacements for the following parts: Primary and secondary interlock switches, interlock monitor switch.

12. If the fuse is blown by the Interlock Monitor Switch: Replace all of the following at the same time: Primary, door sensing switch and power relay, as well as the Interlock Monitor Switch. The correct adjustment of these switches is described elsewhere in this manual. Make sure that the fuse has the correct rating for the particular model being repaired.

13. Design Alteration Warning: Use exact replacement parts only, i.e., only those that are specified in the drawings and parts lists of this manual. This is especially important for the Interlock switches, described above. Never alter or add to the mechanical or electrical design of the MWO. Any design changes or additions will void the manufacturer's warranty.10.Always unplug the unit's AC power cord from the AC power source before attempting to remove or reinstall any component or assembly.

14. Never defeat any of the B+ voltage interlocks. Do not apply AC power to the unit (or any of its assemblies) unless all solid-state heat sinks are correctly installed.

15. Some semiconductor ("solid state") devices are easily damaged by static electricity. Such components are called Electrostatically Sensitive Devices (ESDs). Examples include integrated circuits and field-effect transistors.

Immediately before handling any semiconductor components or assemblies, drain the electrostatic charge from your body by touching a known earth ground.

16. Always connect a test instrument's ground lead to the instrument chassis ground before connecting the positive lead; always remove the instrument's ground lead last.

17. When checking the continuity of the witches or transformer, always make sure that the power is OFF, and one of the lead wires is disconnected.

18. Components that are critical for safety are indicated in the circuit diagram by shading, or .

19. Use replacement components that have the same ratings, especially for flame resistance and dielectric strength specifications. A replacement part that does not have the same safety characteristics as the original might create shock, fire or other hazards.

1. High Voltage Warning Do not attempt to measure any of the high voltages--this includes the filament voltage of the magnetron. High voltage is present during any cook cycle.

Before touching any components or wiring, always unplug the oven and discharge the high voltage capacitor (See Figure 1-1)

2. The high-voltage capacitor remains charged about 30 seconds after disconnection. Short the negative terminal of the high-voltage capacitor to the oven chassis. (Use a screwdriver.)

3. High voltage is maintained within specified limits by close-tolerance, safety-related components and adjustments. If the high voltage exceeds the specified limits, check each of the special components.

1-2

Pretaution

Samsung Electronics

1-2 Special Servicing Precautions (Continued)

1-3 Special High Voltage Precautions

Fig. 1-1. Discharging the High Voltage Capacitor

PRECAUTION

Servicemen should remove their watches whenever working close to or replacing the magnetron.

PRECAUTION

Never touch any circuit wiring with your hand nor with uninsulated tool during operation.

Touch chassis ground first then short to the high voltage capacitor terminal by using screwdriver or jumper wire.

PRECAUTION

There exists HIGH VOLTAGE ELECTRICITY with high current capabilities in the circuits of the HIGH VOLTAGE TRANSFORMER secondary and filament terminals. It is extremely dangerous to work on or near these circuits with the oven energized. DO NOT measure the voltage in the high voltage circuit including filament voltage of magnetron.

H. V. Capacitor

H. V. Diode

Short

2. Specifications

2-1 Table of Specifications

Samsung Electronics 2-1

MODEL MW7491G

ITEM

TIMER 99 MINUTES 99 SECONDS

POWER SOURCE 120V/60HZ, AC

POWER CONSUMPTION MICROWAVE : 1,450W

OUTPUT POWER FROM 100W TO 1000W (10 LEVEL POWER)

(IEC-705 TEST PROCEDURE)

OPERATING FREQUENCY 2,450MHz

MAGNETRON OM75PH(31)ESS

COOLING METHOD COOLING FAN MOTOR

OUTSIDE DIMENSIONS 21

7/8

(W) x 12

5/16

(H) x 16

21/32

(D)

NET WEIGHT 38.6 lbs.

SHIPPING WEIGHT 43 lbs

3-1 Samsung Electronics

Auto Reheat Button

One Minute + Button

Auto Defrost Button

Power Level Selection Button

Clock Button

Pause/Canel Button

Instant Cook Button

Number Key Button

More/Less Button

Start Button

Kitchen Timer Button

Auto

Defrost

Auto

Reheat

Pause

Cancel

Start

Clock

Kitchen

Timer

One Minute +

Popcorn

Diet Cook

Frozen Dinner

More/Less

Power Level

MW7491G

Baby Food

Potato

Fresh

Vegetable

3. Operating Instructions

3-1 Control Panel

3-2 Features & External Views

Door

Ventilation Holes

Light

Safety Interlock Holes

Control Panel

Open Door Push Button

Guide Roller

Glass Tray

Door Latches

556mm

402mm

313mm

260mm

423mm

4. Disassembly and Reassembly

4-1 Replacement of Magnetron, Motor Assembly and Lamp

Samsung Electronics 4-1

Remove the magnetron including the shield case, permanent magnet, choke coils and capacitors (all of which are contained in one assembly).

1. Disconnect all lead wires from the magnetron and lamp.

2. Remove the air cover.

3. Remove screws securing the magnetron to the wave guide.

4. Take out the magnetron very carefully.

5. Remove tow screws from the back panel of fan motor assembly.

6. Take out the fan motor assembly.

7. Remove the oven lamp by pulling out from hole of air cover.

NOTE1: When removing the magnetron, make

sure that its antenna does not hit any adjacent parts, or it may be damaged.

NOTE2: When replacing the magnetron, be sure to

remount the magnetron gasket in the correct position and make sure the gasket is in good condition.

1. Discharge the high voltage capacitor.

2. Disconnect all the leads.

3. Remove the mounting bolts.

4. Reconnect the leads correctly and firmly.

4-2 Replacement of High Voltage Transformer

Lamp

Cover Air

Magnetron

H. V. Trans

H. V. Capacitor

Thermo S/W

Fan Motor

Screw

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