© Panasonic Appliances Microwave Oven(Shanghai) Co., Ltd. 2013.

NN-CS894SBPQ (U.K.)EPG (Continental Europe)WPG (Switzerland)SPG (Norway, Finland, Sweden, Denmark)

Microwave Oven

ORDER NO.PAPMOSH1312045CE

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1 SCHEMATIC DIAGRAM 5 2 DESCRIPTION OF OPERATING SEQUENCE 6

2.1. Variable power cooking control 6

2.2. Inverter power supply circuit 6

2.3. Turbo defrost, Auto cook 6

2.4. Sensor cooking 6

2.5. Sensor and digital programmer circuit 6

2.6. Grill cooking control 7

2.7. Convection cooking control 7

2.8. Steam function 7

3 CAUTIONS TO BE OBSERVED WHEN TROUBLESHOOTING 8 3.1. Check the grounding 8

3.2. Inverter warnings 8

3.3. Part replacement. 8

3.4. Confirm before repair 9

3.5. When the 15A fuse is blown due to the malfunction of the

short switch: 9

3.6. Avoid inserting nails, wire etc. through any holes in the

unit during operation. 9

3.7. Verification after repair 9

3.8. Sharp edges 9

3.9. Hot surface 9

4 DISASSEMBLY AND PARTS REPLACEMENT PROCEDURE 10 4.1. Cabinet body & Rear cover B 10

4.2. H.V. Inverter/Magnetron/Digital programmer circuit (D.P.C.)

(AU)/Fan motor/Stirrer motor 11

4.3. Upper Heater (Heater BU) 16

4.4. Steam Heater (Heater DU) 16

4.5. Door assembly/Digital programmer circuit (D.P.C) (FU) &

(D.P.C) (BU) 17

4.6. Convection motor and convection heater 21

4.7. Pump 23

4.8. Front cover 25

5 COMPONENT TEST PROCEDURE 26 5.1. Primary, Secondary Latch Switch interlocks & Power

Relay RY1 26

5.2. Short Switch 26

5.3. Magnetron 26

5.4. FAN MOTOR 26

5.5. Inverter power supply (U) 27

5.6. Temperature thermistor 27

6 MEASUREMENTS AND ADJUSTMENTS 28 6.1. Adjustment of Primary latch switch, Secondary latch

switch and Short switch. 28

6.2. Measurement of microwave output 29

7 TROUBLESHOOTING GUIDE 30 7.1. (Troubleshooting) Oven stops operation during cooking 30

7.2. (Troubleshooting) Other problems 31

7.3. Troubleshooting of inverter circuit (U) and magnetron 32

7.4. Simple way of H.V. Inverter/magnetron troubleshooting 33

7.5. How to check the semiconductors using an OHM meter 33

7.6. H.V. INVERTER MAIN PARTS LIST (Z606YBH20GP) 34

8 EXPLODED VIEW AND PARTS LIST 35 8.1. EXPLODED VIEW 35

8.2. PARTS LIST 36

8.3. DOOR & ESCUTCHEON BASE ASSEMBLY 38

8.4. WATER TANK ASSEMBLY 39

8.5. WIRING MATERIALS 40

8.6. PACKING AND ACCESSORIES 41

9 DIGITAL PROGRAMMER CIRCUIT 42 9.1. SCHEMATIC DIAGRAM (D.P.CIRCUIT AU) 42

9.2. SCHEMATIC DIAGRAM (D.P.CIRCUIT BU & FU) 44

CONTENTS Page Page

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2.1. Variable power cookingcontrol

High Voltage Inverter Power Supply (U) controls output powerby the signal from Digital Programmer Circuit (DPC). Powerrelay always stay on, but PWM (Pulse Width Modulation) signalcontrols microwave output power.NOTE:

The ON/OFF time ratio does not correspond with thepercentage of microwave power since approximately 2seconds are required for heating of magnetronfilament.

Variable Power CookingPOWERSETTING

OUTPUTPOWER(%)APPROX.

MANUAL MICROWAVE DUTY

ON(SEC) OFF(SEC)1000W 100% 22 0270W 25% 16 6600W 60% 22 0440W 45% 22 0300W 30% 22 0100W 10% 10 12

2.2. Inverter power supply circuitThe Inverter Power Supply circuit powered from the linevoltage, 230V 50Hz AC input supplies 4,000V DC to themagnetron tube, and functions in place of the H.V. transformer,the H.V. capacitor and H.V. diode. 1. The AC input voltage 230V 50Hz is rectified to DC voltage

immediately. 2. DC voltage will be supplied to the switching devices called

IGBT. These devices are switched ON-OFF by the 20 to 40kHz PWM (pulse width modulation) signal from themicrocomputer in the DPC.

3. This drives the High voltage transformer to increase voltageup to 2,000V AC.

4. Then the half-wave doubler voltage rectifier circuit,consisting of the H.V. diodes and capacitors, generates thenecessary 4,000V DC needed for the magnetron.

5. Output power of the magnetron tube is always monitored bythe signal output from the current transformer built into theinverter circuit.

6. This signal is fed back to the microcomputer in the DPC todetermine operating conditions and output necessary tocontrol PWM signal to the Inverter Power Supply for controlof the output power.

2.3. Turbo defrost, Auto cookWhen the Auto Control feature is selected and the Start pad istapped: 1. The digital programer circuit determines the power level and

cooking time to complete cooking and indicates theoperating state in the display window.

2. When cooking time in the display window has elapsed, theoven turns off automatically by a control signal from thedigital programmer circuit.

Turbo DefrostPROGRAM WEIGHT SELECTED COOKING TIME

BREAD 900g 8 min 51 sec.

2.4. Sensor cookingAuto sensor cooking without setting a power level or selectinga time. All that is necessary is to select an Auto SensorProgram before starting to cook.Understanding Auto Sensor Cooking

As the food cooks, a certain amount of steam is produced.If the food is covered, this steam builds up and eventuallyescapes from the container. In Auto Sensor Cooking, acarefully designed instrument, called the steam sensorelement, senses this escape of steam. Then, based uponthe Auto Sensor Program selected, the unit willautomatically determine the correct power level and theproper length of time it will take to cook the food.

NOTE:Auto Sensor Cooking is successful with the foods andrecipes found in the Auto Sensor Cooking Guide.Because of the vast differences in food composition,items not mentioned in the Cooking Guide should beprepared in the microwave oven using power selectand time features. Please consult Variable PowerMicrowave Cookbook for procedures.

2.5. Sensor and digitalprogrammer circuit

In order to determine if the steam sensor function of the digitalprogrammer circuit is working, do the following test. 1. Place a water load (100 cc) in the oven. 2. Tap Auto Sensor pad. 3. Tap Start pad. 4. Sensor detects steam about 0.5 to 1.5 minutes after the

Start pad is tapped. 5. T1 time cooking automatically switches to remaining time

for cooking (T2). 6. The remaining cooking time (T2) appears in display

window. If the following cooking time appears, sensorfunction is normal.

2 DESCRIPTION OF OPERATING SEQUENCE

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2.6. Grill cooking controlGrill cooking is accomplished by upper heaters only. One grillcooking cycle is 33 seconds. 1. During grill cooking, the digital programmer circuit controls

power relay RY3´s ON-OFF time. In all three grill cookingcategories, power relay RY1 always stay ON, but RY3´sON-OFF time are shown in Figure.

GRILLCATEGORY

GRILL (RY3) MICROWAVE (DUTY)ON (sec.) OFF (sec.) ON (sec.) OFF (sec.)

1 33 0 0 332 24 93 18 15

2.7. Convection cooking controlThe digital programmer circuit controls the ON-OFF time of theheater in order to control oven cavity temperature. 1. After selecting desired oven cavity temperature of oven (the

range of selected oven temp is 100°C-230°C) and pressing[Start] pad, a high level signal comes out of the microcomputer and applies to power relays, RY5 & RY3.

2. When RY5 & RY3 are switched to ON, power sourcevoltage is applied to the upper heater & lower heater, andthe heaters turn on.

3. The digital programmer circuit senses the oven cavitytemperature through oven temp sensor (thermistor). Whenthe oven temperature reaches the set temperature, DPCstops supplying high level signal to the power relays, andthe heaters turn off.

4. After the upper heater and lower heater turn off, the oventemperature will continue increasing for a while and thendecrease as shown in Figure.When the oven temperature drops below the settemperature, the digital programmer circuit senses thesignal and starts supplying a high level signal to RY5 & RY3again.

NOTE:If cooking by convection without preheating, upperheater will not turn on.

2.8. Steam function2.8.1. Water SupplyWater in water tank will be pumped out and supply to the steamgeneration heater located left side of oven cavity.

2.8.2. OperationWhen pressing [start] pad, oven preheat will start and thenwater supply begins. When preheat is completed, it will turninto actual cooking process. During heating, the temperaturesensor (Thermistor) located on steam heater will monitor steamheater temperature and when it exceeds a certain level, theadditional water will be supplied to maintain moisture/steamwithin oven cavity.

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Unlike many other appliances, the microwave oven is a highvoltage, high current device. It is free from danger in ordinaryuse, though extreme care should be taken during repair.

CAUTIONServicemen should remove their watches & rings wheneverworking close to or replacing the magnetron.

3.1. Check the groundingDo not operate on a two wire extension cord. The microwaveoven is designed to be grounded when used. It is imperative,therefore, to ensure the appliance is properly grounded beforebeginning repair work.

3.2. Inverter warningsWARNING HIGH VOLTAGE AND HIGHTEMPERATURE

(HOT/LIVE) OF THE INVERTERPOWER SUPPLY (U)The High Voltage Inverter Power Supply generates veryhigh voltage and current for the magnetron tube. Though itis free from danger in ordinary use, extreme care should betaken during repair.The aluminum heat sink is also energized with high voltage(HOT), do not touch when the AC input terminals areenergized. The power device Collector is directly connectedto the aluminum heat sink.The aluminum heat sink may be HOT due to heat energy,therefore, extreme care should be taken during servicing.

H.V. Inverter warningWARNING FOR INVERTER POWER SUPPLY (U)

GROUNDINGCheck the High Voltage Inverter Power Supply circuitgrounding. The high voltage inverter power supply circuitboard must have a proper chassis ground. The invertergrounding plate must be connected to the chassis. If theinverter board is not grounded it will expose the user to veryhigh voltages and cause extreme DANGER! Be sure thatthe inverter circuit is properly grounded via the invertergrounding plate.

WARNING DISCHARGE THE HIGH VOLATGECAPACITORS

For about 30 seconds after the oven is turned off, anelectric charge remains in the high voltage capacitors of theInverter Power Supply circuit board.When replacing or checking parts, remove the power plugfrom the outlet and short the inverter output terminal of themagnetron filament terminals to the chassis ground with aninsulated handle screwdriver to discharge. Please be sureto contact the chassis ground side first and then short to theoutput terminal.

Discharging the high voltage capacitorsWARNINGThere is high voltage present with high current capabilitiesin the circuits of the primary and secondary windings, chokecoil and heat sink of the inverter. It is extremely dangerousto work on or near these circuits with the oven energized.DO NOT measure the voltage in the high voltage circuitincluding the filament voltage of the magnetron.WARNINGNever touch any circuit wiring with your hand or with aninsulated tool during operation.

3.3. Part replacement.When troubleshooting any part or component is to be replaced,always ensure that the power cord is unplugged from the walloutlet.

3 CAUTIONS TO BE OBSERVED WHENTROUBLESHOOTING

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3.4. Confirm before repairCAUTION

To prevent the water from invading the electric parts that can cause ashort circuit or electric shock:1. Before repair or replacement of parts, ensure to remove the water

tank from microwave oven.2. After removing the water tank, select the "drainage" function to

drain the water remaining in the water pipes and tubes into ovencavity forcibly. (Operating method: Tap [Auto Steam] 9 times untilF1 Drain water program appears in the display). Then wipe up theoven cavity.

3. In case the Microwave Oven has no power, the technician shouldhave a dry cloth available in advance before disassembly. Whenpulling out the water tube, elevate the front of the Microwave Ovenat least 1.5” to minimize the amount of water that leaks out. Wipeup excess water throughly with the dry cloth.

WARNINGBefore beginning repair work, make sure that there is nowater in microwave oven, otherwise the water might invadethe electric parts and that can cause a short circuit orelectric shock.

3.5. When the 15A fuse is blowndue to the malfunction of theshort switch:

WARNINGWhen the 15A 250V fuse is blown due to the malfunction ofthe short switch, replace all of the components (primarylatch switch, short switch and power relay RY1). 1. This is mandatory. Refer to “measurements and

adjustments” for the location of these switches. 2. When replacing the fuse, confirm that it has the

appropriate rating for these models. 3. When replacing faulty switches, be sure the mounting

tabs are not bent, broken or deficient in their ability tohold the switches.

3.6. Avoid inserting nails, wire etc.through any holes in the unitduring operation.

Never insert a wire, nail or any other metal object through thelamp holes on the cavity or any holes or gaps, because suchobjects may work as an antenna and cause microwaveleakage.

3.7. Verification after repairCAUTION

After repair or replacement of parts, make sure that all the water pipesand tubes are properly connected, otherwise the water might invadethe electric parts and will cause a short circuit or electric shock.

1. After repair or replacement of parts, make sure that thescrews of the oven, etc. are neither loosen or missing.Microwave energy might leak if screws are not properlytightened.

2. Make sure that all electrical connections are tight beforeinserting the plug into the wall outlet.

3. Check for microwave energy leakage.CAUTION OF MICROWAVE RADIATION LEAKAGE

USE CAUTION NOT TO BECOME EXPOSED TORADIATION FROM THE MICROWAVE MAGNETRON OROTHER PARTS CONDUCTING MICROWAVE ENERGY.

IMPORTANT NOTICE 1. The following components have potentials above 2000V

while the appliance is operated. • Magnetron • High voltage transformer (Located on inverter (U)) • High voltage diodes (Located on inverter (U)) • High voltage capacitors (Located on inverter (U))Pay special attention to these areas.

2. When the appliance is operated with the door hinges ormagnetron installed incorrectly, the microwave leakagecan exceed more than 5mW/cm2. After repair orexchange, it is very important to check if the magnetronand the door hinges are correctly installed.

3.8. Sharp edgesCAUTIONPlease use caution when disassembling or reassemblinginternal parts. Some exposed edges may be sharp to thetouch and can cause injury if not handled with care.

3.9. Hot surfaceCAUTION 1. After using steam function, the oven cavity and steam

heater area becomes very hot. 2. After using convection function, the oven cavity and

convection heater area becomes very hot.Therefore, extreme care should be taken during servicing.

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CAUTIONDischarge the high voltage capacitors first to prevent electricshock.

CAUTIONTo prevent the water from invading the electric parts that can cause ashort circuit or electric shock:1. Before repair or replacement of parts, ensure to remove the water

tank from microwave oven.2. After removing the water tank, select the "drainage" function to

drain the water remaining in the water pipes and tubes into ovencavity forcibly. (Operating method: Tap [Auto Steam] 9 times untilF1 Drain water program appears in the display). Then wipe up theoven cavity.

3. In case the Microwave Oven has no power, the technician shouldhave a dry cloth available in advance before disassembly. Whenpulling out the water tube, elevate the front of the Microwave Ovenat least 1.5” to minimize the amount of water that leaks out. Wipeup excess water throughly with the dry cloth.

CAUTIONAfter repair or replacement of parts, make sure that all the water pipesand tubes are properly connected, otherwise the water might invadethe electric parts and will cause a short circuit or electric shock.

4.1. Cabinet body & Rear cover B 1. Remove 2 screws holding exhaust guide on the oven cavity,

and then remove exhaust guide. 2. Remove 4 screws holding cabinet body on the oven cavity,

then remove cabinet body.

3. Remove 5 screws holding rear cover B.

4 DISASSEMBLY AND PARTS REPLACEMENTPROCEDURE

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4.2. H.V. Inverter/Magnetron/Digitalprogrammer circuit (D.P.C.)(AU)/Fan motor/Stirrer motor

1. Discharge high voltage remaining in high voltage capacitor. 2. Turn over the microwave oven. 3. Remove total 12 screws as below steps.

a. Remove 5 screws holding base plate on the bottom ofoven cavity front plate.

b. Remove 2 screws holding base plate on the bottom ofoven cavity rear plate.

c. Remove 4 screws holding left and right hinges.NOTE:

Do not remove the two screws holding the leftand right hinges on the bottom of cavity frontplate.

d. Remove 1 screw holding air guide D on base plate.

4. Remove left and right door key springs from door arm.NOTE:Support door before removing door springs.

5. Disconnect the connector from convection fan motorterminals.

6. Turn over microwave oven to make front side facing up. 7. Disconnect connector from D.P.C.(AU) board.

8. Disconnect 2 high voltage lead wires from magnetronfilaments terminals.

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4.2.1. To replace magnetron

1. Remove air guide D. 2. Remove 2 screws holding air guide F. 3. Remove 1 screw holding thermistor on magnetron. 4. Remove 3 screws holding magnetron.

NOTE:After replacement of the magnetron, tightenmounting screws properly, making sure there is nogap between the waveguide and the magnetron toprevent microwave leakage.

CAUTIONWhen replacing the magnetron, be sure the antenna gasket is inplace.

4.2.2. To replace H.V Inverter 1. Release 4 catch hooks, then remove inverter cover.

2. Remove 2 screws holding H.V. Inverter.

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4.2.3. To replace Digital programmercircuit D.P.C.(AU) board

CAUTION:Be sure to ground any static electric charge built up inyour body before handling the D.P.C.

1. Release 7 catch hooks, then remove PCB cover.

2. Remove 4 screws holding D.P.C.(AU) board.

4.2.4. Low voltage transformer and/orpower relays

CAUTION:Be sure to ground any static electric charge built up inyour body before handling the DPC.

1. Using solder wick or a desoldering tool and 30W solderingiron carefully remove all solder from the terminal pins of thelow voltage transformer and/or power relays.NOTE:

Do not use a soldering iron or desoldering tool ofmore than 30 watts on D.P.C. contacts.

2. With all the terminal pins cleaned and separated fromD.P.C. contacts, remove the defective transformer/powerrelays, Replace components making sure all terminal pinsare inserted completely resolder all terminal contactscarefully.

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4.2.5. To replace fan motor 1. Disconnect connector of fan motor.

2. Remove 2 screws holding fan case (U) .

3. Remove 3 screws to seperate fan motor from fan casecover.

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4.2.6. To remove stirrer motor 1. Remove 2 screws holding motor bracket.

2. Pull out shaft from stirrer motor.

3. Disconnect connector from stirrer motor.

4. Remove 2 screws holding stirrer motor on the motorbracket.

To install stirrer motor 5. When you insert the motor shaft, make sure to match the

convex edge to the concave edge.

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4.3. Upper Heater (Heater BU) 1. Remove 4 screws holding left and right heater bracket on

oven cavity, then remove both 2 heater brackets.

2. Remove 2 screws from both side of upper heater.

3. Remove the heater by pulling it out slightly.

4.4. Steam Heater (Heater DU) 1. Draw out water tank (U) from drip tray. 2. After removing the water tank, select the "drainage"

function to drain the water remaining in the water pipes andtubes into oven cavity forcibly. (Operating method: Tap[Auto Steam] 9 times until F1 Drain water program appearsin the display). Then wipe up the oven cavity.

3. Disconnect 2 connectors from steam heater terminals.

4. Remove 1 screw holding thermistor on steam heater.

5. Remove 1 screw holding thermal cutout bracket on steamheater.

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6. Remove 3 screws holding steam heater on oven assy.

7. Raise steam heater slightly and take out steam heater. 8. Pull out 3 pipes slightly.

To install thermistorNOTE:Before installing thermistor, please fill enough silicongrease into the installation hole of steam heater forgood conductibility.

NOTE:To prevent pipe from slipping out after repairing, makesure that insert the pipe all the way to the end.

4.5. Door assembly/Digitalprogrammer circuit (D.P.C)(FU) & (D.P.C) (BU)

1. Remove left and right door key springs from door arm withplier.NOTE:

Support door before removing door springs.

4.5.1. To remove door C and door A • Insert flat blade screwdriver to release hinge pin from

left hinge. • Release catch hooks between door C and door A, to

detach the door C.

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1. Release 2 catch hooks to turn out the harness protector´scover horizontally from the right side of oven cavity.

2. Remove 1 screw holding harness protector on right hinge(U).

3. Disconnect 1 connector from D,P.C. (AU) board.

4. Draw out harness protector slightly in direction of arrows.

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5. Release the catch hooks on harness protector to seperatelead wire harness from harness protector.

6. Slide the door (U) left and right to release the pin from doorhinge, then remove door (U) from oven cavity. • Draw out the lead wire harness toward the front side of

the unit.

7. Remove 8 screws holding door E on door A (U).

NOTE:After replacement of the defective component parts ofthe door, reassemble it properly and adjustment so asto prevent an excessive microwave leakage.Adjustment of the door assembly(Refer page 28).

1. When mounting the door to the oven, be sure to adjust thedoor parallel to the cavity front plate by moving hinges backor forward.

2. Adjust so that the upper portion of the door will touch firmlyto the oven cavity front plate, without pushing the door.If the door assembly is not mounted properly, microwavepower may leak from the clearance between the door andoven.

3. Be sure the gap between left or right portion of doorassembly and cavity front plate will be 1.0±0.3mm.

4. Always perform the microwave leakage measurement testafter installation and adjustment of door assembly.

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4.5.2. To replace D.P.C. (FU) board 1. Remove 2 screws holding heat insulation panel.

2. Remove 6 screws holding escutcheon base.

4.5.3. To replace door screen B (U) 1. Remove 6 screws holding door handle (U) on door A (U).

2. Remove door screen B (U) from door A (U).(Note: a D.P.C. board is paste on the door screen B (U))

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4.5.4. To replace fan motor (BU) 1. Release catch hooks and pull out fan motor (BU).

4.6. Convection motor andconvection heater

1. Remove 5 screws holding rear cover B.

2. Remove 2 screws from the convectin heater terminals.

3. Release the harness from clip.

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4. Disconnect the connectors from convection fan motorterminals and thermal cutout terminals.

5. Remove 1 screw holding exhaust guide A.

6. Remove 14 screws holding convection module on ovencavity.

7. Remove 2 screws holding convection module on baseplate.

4.6.1. To replace convection heater 1. Remove 2 screws holding convection heater from

convection fan cover.

2. Remove 3 screws holding heater bracket, then removeconvection heater.

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4.6.2. To replace convection fan motor 1. Remove 1 nut holding convection fan blade, then remove

convection fan blade. 2. Remove 3 screws holding convection fan bracket.

3. Remove 2 screws holding convection fan motor.

4.7. Pump 1. Draw out water tank (U) from drip tray. 2. After removing the water tank, select the "drainage"

function to drain the water remaining in the water pipes andtubes into oven cavity forcibly. (Operating method: Tap[Auto Steam] 9 times until F1 Drain water program appearsin the display). Then wipe up the oven cavity.

3. Disconnect 1 connector from the pump motor. 4. Remove 4 screws fixing water tank holder on the bottom of

base plate.

5. Press the tab by using a flathead screwdriver (through thehole at a 45° angle) to release catch hook.Then remove the whole water tank holder.

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6. Remove 1 screw fixing the cover of water tank holder.

7. Release 2 locking tabs to open the cover.

8. The matching relationship between tank (U), pump motorand water tank holder are as the illustration below.

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To install pump motor 1. Insert pump motor into water tank holder. 2. Make sure that the pump motor is properly aligned after

installation.

NOTE:To prevent tube B from slipping out after repairing,make sure the insert depth should be proper wheninserting tube B into nozzle A.

4.8. Front cover4.8.1. How to remove the fornt cover 1. Lightly twist the cover until the far side unclips. 2. Continue to twist until the near side unclips.

4.8.2. How to re-fitting the front cover 1. Align the slots on the cover with the holes on the tank. 2. Insert and push down until it clicks.

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WARNING1. High voltage is present at the output terminals of the High VoltageInverter (U) including aluminum heat sink during any cook cycle.2. It is neither necessary nor advisable to attempt measurement of thehigh voltage.3. Before touching any oven components, or wiring, always unplugthe power cord and discharge the high voltage capacitors (see page8).

5.1. Primary, Secondary LatchSwitch interlocks & PowerRelay RY1

1. Unplug lead connectors to Power Relay RY1 and verifyopen circuit of the Power Relay RY1 1-2 terminals.

2. Unplug lead connectors to Primary Latch Switch andSecondary Latch Switch.

3. Test the continuity of switches at door opened and closedpositions with ohm meter (low scale).Normal continuity readings should be as follows.

Door Closed Door OpenedPrimary Latch Switch 0Ω (Close) Ω(Open)Secondary Latch Switch 0Ω (Close) Ω(Open)Power Relay RY1 Ω (Open) Ω(Open)

5.2. Short Switch 1. Unplug lead wires from Inverter Power Supply (U) primary

terminals. 2. Connect test probes of ohm meter to the disconnected

leads that were connected to Inverter Power Supply (U). 3. Test the continuity of short switch with door opened and

closed positions using lowest scale of the ohm meter.Normal continuity readings should be as follows.

Door Opened Door Closed0Ω (Close) Ω (Open)

5.3. MagnetronContinuity checks can only indicate an open filament or ashorted magnetron. To diagnose for an open filament orshorted magnetron. 1. Isolate magnetron from the circuit by disconnecting the

leads. 2. A continuity check across magnetron filament terminals

should indicate one ohm or less. 3. A continuity check between each filament terminal and

magnetron case should read open.

5.4. FAN MOTOR 1. connection

2. Control wire of fan motor should accept PWM control.Fan motor´s spin speed is controlled by this PWM siginal.PWM frequency is from 10KHz to 30 KHz. If the PWMcontrol wire open, fan motor will spin at maximum speed.

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5.5. Inverter power supply (U)DO NOT try to REPAIR H.V. Inverter power supply(U).Replace complete H.V. Inverter(U) Unit.

WARNING: HIGH VOLTAGETest if failure codes H95, H97 or H98 appear when performingthe following procedure. It is recommended to use an AC lineinput current ammeter for testing.Test 1 1. With the oven unit’s AC power supply cord is unplugged

from the wall outlet, unplug the 2 pin H.V. connector CN703from the magnetron tube.

2. Place 1 liter of water load into oven cavity. 3. Plug in the oven’s AC power supply cord into outlet. 4. Program DPC.

a. Press Timer pad twice. b. Press Start pad once. c. Press Micro Power pad once.

5. Program oven at High power for 1 minute and press [Start]pad. a. After approximately 23 seconds, oven stops operating. b. During oven operation, the input current is

approximately 0.5 to 1A. If both a and b are OK,proceed to test 2.

INPUT CURRENT FAILURE CODEUnplug CN703 0.5 to 1A Oven stops in 23

seconds after started.

Test 2Continued from Test 1 1. Unplug the oven’s AC power supply cord from outlet. 2. Unplug 3 pin connector CN701. CN703 remains unplugged. 3. Plug in the oven’s AC power supply cord into outlet. 4. Program DPC.

a. Press Timer pad twice. b. Press Start pad once. c. Press Micro Power pad once.

5. Program oven at High power for 1 minute and press [Start]pad.

a. After approximately 3 seconds, oven stops operating. b. During oven operation, the input current is

approximately 0.4A.

INPUT CURRENT FAILURE CODEUnplug CN701 0.4A Oven stops in 3

seconds after started.

If both a and b check OK, the Inverter Power Supply (U) can bedetermined to be OK.

5.6. Temperature thermistorThe thermistor that is attached to the magnetron detects thetemperature of the magnetron and will stop magnetronoperation when overheating is detected. A normal thermistor´sresistance is 35KΩ to 110KΩ for an ambient temperature rangeof 10-30 degree C.If the resistance reading is out of the range stated here, thethermistor is detective and must be replaced.It is also possible to display thermistor level by taking thefollowing steps. 1. Program the DPC into TEST MODE (Plug-in oven → press

Timer pad twice → press Start pad once → pressMicro Power pad once).

2. Program oven at Standing Time for 1 minute and press[Start] pad.

3. Press Reheat twice, the thermistor level reading willshown on the display.The normal reading should be in the range of 16-230.

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6.1. Adjustment of Primary latchswitch, Secondary latchswitch and Short switch.

1. Mount the Primary latch switch, the Secondary latch switchand the Short switch to the door hook assembly as shownin illustration.NOTE:

No specific individual adjustments duringinstallation of the Primary latch switch, Secondarylatch switch or Short switch to the door hook arerequired.

2. When mounting the door hook assembly to the ovenassembly, adjust the door hook assembly by moving it inthe direction of the arrows in the illustration so that the ovendoor will not have any play in it. Check for play in the doorby pulling the door assembly. Make sure that the latch keysmove smoothly after adjustment is completed. Completelytighten the screws holding the door hook assembly to theoven assembly.

3. Reconnect the short switch and check the continuity of themonitor circuit and all latch switches again by following thecomponent test procedures.

4. The Primary latch switch must be ON when the spacebetween upper portion of door A and cavity front plate is2~4mm, if the door gap is greater than 4mm, the Primarylatch switch must be OFF.

If alignment is poor, oven may not operate afterconvection/grill use.

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6.2. Measurement of microwaveoutput

The output power of the magnetron can be determined byperforming IEC standard test procedures. However, due to thecomplexity of IEC test procedures, it is recommended to testthe magnetron using the simple method outlined below.Necessary Equipment: • 1 litre beaker • Glass thermometer • Wrist watch or stopwatchNOTE:

Check the line voltage under load. Low voltage willlower the magnetron output. Take the temperaturereadings and heating time as accurately as possible.

1. Fill the beaker with exactly one litre of tap water. Stir thewater using the thermometer and record the water’stemperature. (recorded as T1).

2. Place the beaker on the center of glass tray.Set the oven for High power and heat it for exactly oneminute.

3. Stir the water again and read the temperature of the water.(recorded as T2).

4. The normal temperature rise at High power level for eachmodel is as shown in table.

TABLE (1L-1min.test)RATED OUTPUT TEMPERATURE RISE

1000W Min.8.5°C

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7 TROUBLESHOOTING GUIDEDANGER: HIGH VOLTAGES

1. DO NOT RE-ADJUST PRESET CONTROL on the H.V.Inverter (U). It is very dangerous to repair or adjust without proper test equipmentbecause this circuit generates very large current and high voltage. Operating a misaligned inverter circuit is dangerous.

2. Ensure proper grounding before troubleshooting.3. Be careful of the high voltage circuitry, taking necessary precautions when troubleshooting.4. Discharge high voltage remaining in the H.V.Inverter (U).5. When checking the continuity of the switches or the H.V.Inverter, disconnect one lead wire from these parts and then check continuity with the

AC plug removed. Doing otherwise may result in a false reading or damage to your meter. When disconnecting a plastic connector from aterminal, you must hold the plastic connector instead of the lead wire and then disconnect it, otherwise lead wire may be damaged or theconnector cannot be removed.

6. Do not touch any parts of the circuitry on the digital programmer circuit, since static electric discharge may damage this control panel. Alwaystouch ground while working on this panel to discharge any static charge in your body.

7. 230V AC is present on the digital programmer circuit (Terminals of power relay’s and primary circuit of Digital Programmer Circuit). Whentroubleshooting, be cautious of possible electrical shock hazard.

Before troubleshooting, operate the microwave oven following the correct operating procedures in the instruction manual in orderto find the exact cause of any trouble, since operator error may be mistaken for the oven’s malfunction.

7.1. (Troubleshooting) Oven stops operation during cookingSYMPTOM CAUSE CORRECTIONS

1. Oven stops in 3 seconds afterpressing [start] pad.

No input AC is supplied to H.V.Inverter (U)CN702 terminals

1.2.3.

Latch SwitchPower relay RY1Loose lead wire connector CN701, CN702

Oven stops in 23 seconds afterpressing [start] pad.

H.V.Inverter (U) operates by the control signalsfrom DPC but magnetron is not oscillating

1.2.

MagnetronLoose lead wire connector CN703

Oven stops in 1 minute afterpressing [start] pad.

Oven thermistor circuit is not functioning 1.2.

Oven thermistorLoose wiring

Oven stops in 3 minutes afterpressing [start] pad.

Magnetron thermistor circuit is not functioning 1.2.

Magnetron thermistorLoose wiring

Oven stops in 30 seconds afterpressing start pad. (Steam cooking)

Steam heater thermistor circuit is notfunctioning.

1.2.3.

Steam heater thermistorLoose wiringBad conductibility between thermistor and steamheater

2. No display and no operation at all.Fuse is blown.

Most probably loose connection of connectors,or door latch mechanism is not adjusted properly

1.2.

Align door, Door Latch SwitchesLoose wiring connectors

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7.2. (Troubleshooting) Other problemsSYMPTOM CAUSE CORRECTIONS

1. Oven is dead. 1. Open or loose lead wire harnessFuse is OK. 2. Open thermal cutout / thermistor Check thermal cutout is defective.No display and no operation at all. 3. Open low voltage transformer

4. Defective DPC2. No display and no operation at all.

Fuse is blown.1. Shorted lead wire harness Check adjustment of primary, secondary latch

switch and short switch including door.2. Defective primary latch switch (NOTE 1)3. Defective short switch (NOTE 1)4. Defective Inverter Power Supply (U)

NOTE 1:All of these switches must be replaced at the same time.Check continuity of power relay RY1 contacts (between 1 and 2) and if it has continuity, replacepower relay RY1 also.

3. Oven does not accept key input(Program)

1. Key input is not in proper sequence Refer to operation procedure.2. Open or loose connection of D.P.C. BU to

D.P.C. FU (Flat cable)3. Defective D.P.C.4. Defective touch screen

4. Timer starts count down but nomicrowave oscillation.(No heat while oven lamp and fanmotor turn on)

1. Off-alignment of primary latch switch Adjust door and latch switches.2. Open or loose connection of high voltage

circuit especially magnetron filament circuitNOTE:Large contact resistance will cause lowermagnetron filament voltage and causemagnetron to have lower output and/or beintermittent.

3. Defective high voltage componentH.V. Inverter Power Supply (U)Magnetron

Check high voltage component according tocomponent test procedure and replace if it isdefective.

4. Open or loose wiring of power relay RY15. Defective primary latch switch6. Defective DPC or power relay RY1 Refer to DPC troubleshooting

5. Oven can program but timer does notstart countdown.

1. Open or loose wiring of secondary latch switch2. Off-alignment of secondary latch switch3. Defective secondary latch switch

6. Microwave output is low. Oven takeslonger time to cook food.

1. Decrease in power source voltage Consult electrician2. Open or loose wiring of magnetron filament

circuit.(Intermittent oscillation)3. Aging change of magnetron

7. Oven does not operate and return toplugged in mode as soon as [Start]button is pressed.

1. Defective DPC Check grounding connector on escutcheonbase.

8. Loud buzzing noise can be heard. 1. Loose fan and fan motor9. Heater does not turn on. 1. Open or loose wiring of heater

2. Defective heater3. Defective power relay4. Defective DPC

10. Oven stops operation during cooking. 1. Open or loose wiring of primary andsecondary latch switch

Adjust door and latch switches.

2. Operation of thermal cutout

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7.3. Troubleshooting of inverter circuit (U) and magnetronThis oven is programmed with a self diagnostics failure code system which will help for troubleshooting. H95, H97, H98 and H99are the provided failure codes to indicate magnetron and inverter circuit problem areas. This section explains failure codes of H95,H97, H98 and H99. First, you must program the DPC into TEST MODE, press Timer pad twice → press Start pad once → pressMicro Power pad once. Program unit for operation. H95, H97, H98, H99 appears in display window a short time after [Start] pad

is pressed and there is no microwave oscillation.

Alternate way to troubleshoot oven with AC Ampere meter used

H95, H97, H98, H99 appears in display window a short time after [Start] pad is pressed and no microwave oscillation with ACAmpere meter used for troubleshooting.

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7.4. Simple way of H.V. Inverter/magnetron troubleshootingPurpose:

Simple way (3/23 seconds rule) of identifying whether it’s Magnetron, Inverter, or others.Set-up:

The unit under question is connected through the Ammeter as shown below.

Procedure:Follow the matrix table below to identify the problem source.

Note:Do not replace both Inverter board and Magnetron simultaneously and automatically without going through thisprocedure.

Power will: Ammeter reading is: To do: Remedy:Shut off in 23 secondsafter “Start”.

1. Between 0.5A and 1.0A. Check and repair open magnetron circuit Open magnetron wiring between Inverterand magnetron terminal.

2. Between 1.0A and 2.0A. Check continuity of D702 in Inverter PCB.

1. D702 shorted Replace H.V.Inverter(Z606YBH20GP)

2. D702 is OK Replace magnetronShut off in 3 secondsafter “Start”

1. Less than 0.5A Check open circuit: Latch Switch, DPC,Power Relay and CN701

Replace defective component(s), orcorrect switch, cables and connectors.

7.5. How to check the semiconductors using an OHM meter

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7.6. H.V. INVERTER MAIN PARTS LIST (Z606YBH20GP)Ref. No. Part No. Part Name & Description Pcs/Set Remarks

Q701 Z1JAEV000003 IGBT 1C701 ZCWHC3B104JA FILM CAPACITOR 1 0.1µF,1000VDCC702 ZCWF4305N851 FILM CAPACITOR 1 3µF,250VDC

DB701 Z0FBBQ000006 RECTIFIER BRIDGE 1L701 Z5020W100AP CHOKE COIL 1R702 Z0CM562JA002 SAND BAR RESISTOR 1 5.6KΩ,15WT701 Z609ABA00GP TRANSFORMER 1 (INCLUDING D701,D702,C706,C707)

D701,D702 Z0FBAZ000006 DIODE 2C706 Z0C3F562A002 FILM CAPACITOR 1 5600PF/3KVC707 Z0C3F822A002 FILM CAPACITOR 1 8200PF/3KV

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