Sharp MMD24S, MMD24B Test Procedures, Letter, A Touch Control Panel Assembly Test, Before testing

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TEST PROCEDURES

TEST PROCEDURES

PROCEDURE

COMPONENT TEST

LETTER

 

ATOUCH CONTROL PANEL ASSEMBLY TEST

MMD24S

MMD24B

The touch control panel consists of circuits including semiconductors such as LSI, ICs, etc. Therefore, unlike conventional microwave ovens, proper maintenance cannot be performed with only a voltmeter and ohmmeter.

In this service manual, the touch control panel assembly is divided into three units, Control Unit, Keyboard Unit and Power Unit, and troubleshooting by unit replacement is described according to the symptoms indicated.

Before testing,

1)Disconnect the power supply cord, and then disassemble as per "MICROWAVE DRAWER DISASSEMBLY" page 27.

2)Open the drawer and block it open.

3)Discharge high voltage capacitor.

4)Disconnect the leads to the primary of the power transformer.

5)Ensure that these leads remain isolated from other components and oven chassis by using insulation tape.

1.Keyboard Unit. NOTE ;

1)Check Keyboard unit connection before replacement.

2)Reconnect all leads removed from components during testing.

3)Re-install the covers.

4)Reconnect the power supply cord after the covers are installed.

5)Run the oven and check all functions.

The following symptoms indicate a defective keyboard unit.

a)When touching the pads, a certain pad produces no signal at all.

b)When touching a number pad, two figures or more are displayed.

c)When touching the pads, sometimes a pad produces no signal. If the Keyboard unit is defective.

1) Disconnect the power supply cord, and then remove covers.

2) Open the drawer and block it open.

3) Discharge high voltage capacitor.

4) Replace the Keyboard unit.

5) Reconnect all leads removed from components during testing.

6) Re-install the covers.

7) Reconnect the power supply cord after the covers are installed.

8) Run the oven and check all functions.

2.Control Unit

The following symptoms indicate a defective control unit. Before replacing the control unit, perform the Keyboard unit test (Procedure B) to determine if control unit is faulty.

2-1 In connection with indicators

a)At a certain digit, all or some segments do not light up.

b)At a certain digit, brightness is low.

c)Only one indicator does not light.

d)The corresponding segments of all digits do not light up; or they continue to light up.

e)Wrong figure appears.

f)A certain group of indicators do not light up.

g)The figure of all digits flicker.

2-2 Other possible problems caused by defective control unit.

a)Buzzer does not sound or continues to sound.

b)Clock does not operate properly.

c)Cooking is not possible.

3.Power Unit or Touch Control Transformer

a)Fan motor, stirrer motor, oven lamp or electrical parts do not turn on or do not turn off.

b)Digital display on the control unit does not show anything.

When testing is completed,

1)Disconnect the power supply cord, and then disassemble as per "MICROWAVE DRAWER DISASSEMBLY" page 27.

2)Open the drawer and block it open.

3)Discharge high voltage capacitor.

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Contents MICROWAVE MEASUREMENT PROCEDURE TABLE OF CONTENTSWARNING TO SERVICE PERSONNEL WARNING TO SERVICE PERSONNELBEFORE SERVICING When the testing is completed WARNING TO SERVICE PERSONNELAfter repairing Before ServicingC. Leakage test MICROWAVE MEASUREMENT PROCEDUREB. Preparation for testing A. RequirementsIf provided, Vent Hood, Fan assembly, Cooling Fan Motor DANGER1440 Bridge Gate Dr Diamond Bar, CA SERVICE MANUALDESCRIPTION MICROWAVE DRAWER SPECIFICATIONGROUNDING INSTRUCTIONS GENERAL INFORMATIONOFF CONDITION POWER LEVEL P-0 TO P-90 COOKINGOPERATION DESCRIPTION OF OPERATING SEQUENCEMICROWAVE SENSOR COOKING CONDITIONCooking Sequence DOOR SCHEMATIC OFF CONDITIONCLOSED, COOK OFF CONDITTION Before testing TEST PROCEDURESPROCEDURE A TOUCH CONTROL PANEL ASSEMBLY TESTC RELAY TEST COMPONENT TESTB KEY UNIT TEST The rated AC voltage is not present between Check supply voltage and oven power cordDEFROST TEST STEPSWater load cooking test TESTING METHOD FOR AH SENSOR AND/OR CONTROL UNITF AH SENSOR TEST Checking the initial sensor cooking condition R1, R2 22Ω ± 1% 1/2W R3 4.3kΩ ± 5% 1/4W R4 1MΩ ± 5% 1/4W CHECKING CONTROL UNITH THERMAL CUT-OUT TEST Refer to the disassembly instructions found on PageG MAGNETRON ASSEMBLY TEST MICROWAVE OUTPUT POWERK MONITOR SWITCH TEST I SECONDARY INTERLOCK SWITCH TESTJ STOP SWITCH TEST L BLOWN MONITOR FUSE TEST M POWER TRANSFORMER TEST5 Indicator Circuit TOUCH CONTROL PANEL ASSEMBLYControl Unit and Power Unit 4 Reset CircuitPower source voltage +5V DESCRIPTION OF LSI IC-1Power source voltage 0V GND Internal clock oscillation frequency setting inputSignal similar to P23 SignalSegment data signal Signal coming from touch keySignal to synchronize LSI with commercial power source frequency Magnetron high-voltage circuit driving signalCommon relay driving signal. Square Waveform 60Hz Signal to sound buzzer2 Operational Principle of Humidity Sensor HUMIDITY SENSOR CIRCUITventilation opening for sensing 1 Structure of Humidity Sensor2. Servicing of Touch Control Panel TOUCH CONTROL PANEL SERVICING1 Servicing the touch control panel with power supply of the oven 4. Other Precautions3. Soldering PRECAUTIONS FOR USING LEAD-FREE SOLDER2. Using lead-free wire solder 1. Employing lead-free solderTo prevent an electric shock, take the following pre- cautions COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDUREWARNING FOR WIRING WARNING AGAINST HIGH VOLTAGEMICROWAVE DRAWER DISASSEMBLY Un-hook/Attach Ground to metal Tab on Back Plate POWER CORD REPLACEMENTUn-hook/Attach Black AC Wire to Top Terminal Un-hook/Attach White AC Wire to Bottom TerminalAfter adjustment, check the following STOP SWITCH, SECONDARY INTERLOCK SWITCH AND MONITOR SWITCH REMOVALSTOP SWITCH, SECONDARY INTERLOCK SWITCH AND MONITOR SWITCH ADJUSTMENT Re-install1. Follow the Microwave Drawer disassembly as previously DRAWER ASSEMBLY AND CHOKE REMOVALDRAWER SUPPORT ANGLE REMOVAL DRAWER/SLIDE RAIL REMOVALActuator adjustment SWITCH ANGLE REMOVAL/ADJUSTMENTSWITCH ANGLE REMOVAL ACTUATOR REMOVAL/ADJUSTMENTInstallation AUTO DRAWER GEAR REMOVAL/INSTALLATIONBottom cover RACK GEAR REMOVALto Back Plate HIGH VOLTAGE COMPONENTSCN-A Figure S-2. Power Unit CircuitMICRO FM AF G H UNITCONTROL UNITA B C D E F G H Figure S-4. Printed Wiring Board of Power Unit2.5A UnitControlof 5.PrintedWiringBoardCOPYRIGHT 2008 BY DACOR, INC ALL RIGHTS RESERVED
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