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5

4 Inverter Warnings

The inverter circuit board supplies the magnetron tube with a very high voltage (4000 volts).

Danger

• The inverter circuit board operates at high voltages 

and high temperatures.

The Inverter PCB

• Operates at a very high voltage and current.
• Has an aluminium heat sink which becomes very 

hot.

• Has capacitors in the circuitry that hold a high volt-

age charge even when the oven is not operating. 

Warning

• Do not touch the high voltage circuit. When replac-

ing the board care must be taken to avoid possible 
electric shock. 

• Do not touch the aluminium heat sink as it is part of 

the high voltage circuit and becomes very hot.

• Do not attempt to repair the inverter PCB, this 

can be very dangerous.  Replace the high volt-
age inverter circuit as a complete unit.

• Do not adjust or tamper with the pre-set volume on 

the inverter board. It is very dangerous to adjust 
this pre-set without proper test equipment.

• Do not operate the microwave oven when the 

inverter grounding plate and fixing screw is loose.  
It is very dangerous to operate the inverter circuit 
board without a proper ground connection.

figure 1Assembly of the inverter circuit board

HEAT SINK

RECTIFIER BRIDGE

CHOKE COIL

SAND BAR RESISTOR

CURRENT TRANSFORMER

HIGH VOLTAGE TRANSFORMER

PRESET VOLUME *4

(DO NOT ADJUST)

FILM CAPACITORS

HIGH VOLTAGE

DIODES

HIGH VOLTAGE

CAPACITORS

CN 703

CN 701

CONTROL BOARD

WITH CUSTOM IC

PHOTOCOUPLER

DO NOT TOUCH

HOT/HIGH VOLTAGE *2

HIGH VOLTAGE AREA *1

Содержание Inverter NN-A524MBBTQ

Страница 1: ...80W Convection 1390W Micro Grill Combi 2380W Micro Conv Combi 2390W Output IEC60705 Microwave 1000W Grill 1300W Convection 1300W Microwave frequency 2450 Mhz Timer 99 min 99 second Oven cavity size 27L Outside dimensions 510mm W x 390mm D X 305MM H Inside dimensions 359mm W X 352mm D x 217mm H Weight 13Kg Specifications subject to change without notice ...

Страница 2: ...n warnings or cautions to advise non technical individuals of potential dangers in attempting to service a product Products powered by electricity must be serviced or repaired only by expe rienced proffesional technicians Any attempt to service or repair the product or products dealt with this service information by anyone else could result in serious injury or death There are special components u...

Страница 3: ...Function All Models Microwave 6 Grill 3 Convection 13 Combi Yes Weight reheat 4 Weight cook 2 Weight combination 1 Weight defrost 3 Auto Preheat 3 Delay Stand Yes Kg lb Yes Stage Cooking 3 Clock 12 h Word prompt English ...

Страница 4: ...ock Pad 12 lb oz Conversion Pad 13 Weight Selection Pads 14 Stop Cancel Pad Before Cooking one press clears your instructions During Cooking one press temporarily stops the cooking program Another press cancels all your instructions and the time of day will appear in the display 15 Start Pad Press to start operating the oven If during cooking the door is opened or Stop Cancel Pad is pressed once S...

Страница 5: ...es very hot Do not attempt to repair the inverter PCB this can be very dangerous Replace the high volt age inverter circuit as a complete unit Do not adjust or tamper with the pre set volume on the inverter board It is very dangerous to adjust this pre set without proper test equipment Do not operate the microwave oven when the inverter grounding plate and fixing screw is loose It is very dangerou...

Страница 6: ...6 5 Schematic Diagram ...

Страница 7: ...HE COLOUR O THE CONNECTOR HOUSIN MA NETRON HI H OL TA E IN ER TER CAUTION HEAT SINK HOT LI E ER Y HI H OL TA E AND TEMPERATURE BR BR BR OR 1 C2 PRIMARY LATCH SWITCH TOP WH WH WH SECONDARY LATCH SWITCH OUTSIDE BOTTOM BR N YE YE SHORT SWITCH INSIDE BOTTOM YE BL POWER RELAY RY1 N 2 1 BL SYMBOL COLOUR BL BLUE BK BLACK BR BROWN WH WHITE YE YELLOW N NATURAL R RED R ...

Страница 8: ...ermines the power level and the cooking time and indicates the operating state in the display The table shows the corresponding cooking times and weights for the selected category 2 When the cooking time in the display window has elapsed the oven turns off automatically via the control signal from the digital programmer circuit Note After auto cooking if the oven temperature is over the predetermi...

Страница 9: ...gerous The aluminium heat sink is also energized with high voltage never touch this heat sink when the micro wave oven is plugged into the mains outlet The collec tor of the power device IGBT is directly connected to the aluminium heat sink The aluminium heat sink becomes very hot when the inverter circuit operates Never touch this heat sink during operation and allow time for it to cool down befo...

Страница 10: ...and the primary latch switch when the 10A 250V fuse is blown due to the operation of the short switch It is also important to change the power relay 1 RY1 when the continuity test shows shorted contacts 1 This is mandatory Refer to adjustments and meas urements for the location of these switches 2 When replacing the fuse confirm that it has the appropriate rating for these models 3 When replacing ...

Страница 11: ...n reach more than 5mW cm3 After repair or replac ing parts it is very important to check if the magnetron and the door hinges are correctly fixed 8 7 Sharp edges Please use caution when unpacking installing or mov ing the unit as some exposed edges may be sharp to touch and cause injury if not handled with care ...

Страница 12: ... 2 Inverter circuit 1 Discharge the high voltage capacitors 2 Remove 2 screws holding the tie bar 3 Unplug the H V Lead wires from the magnetron 4 Remove the 1 screw holding the earth wire to the magnetron 5 Remove the connector CN701 and CN702 from the inverter PCB figure 8 6 Remove the 2 screws holding the inverter support base to the oven chassis 7 Carefully remove the inverter circuit board an...

Страница 13: ...ote Ground your body to discharge static charges before handling the DPC 1 Carefully remove all solder from the terminal pins of the low voltage transformer power relays using a 30W soldering iron and a solder sucker 2 With all of the terminal pins cleaned and separated from the DPC contacts remove the defective trans former power relays and install the new compo nents making sure that the termina...

Страница 14: ...le Motor 1 Remove the motor cover by breaking it off at the 8 spots indicated by the arrows 2 Disconnect the two lead wires connected to the turntable motor 3 Remove the 2 screws holding the turntable motor Note After breaking off the motor cover make sure no sharp edges are exposed by trimming off the edges or bending them inside Note To secure the motor cover use a 4 x 6 screw figure 13 Removing...

Страница 15: ...r to these leads 3 Test the continuity of the short switch with the door open and the door closed using a ohm meter set to the lowest resistance scale 10 3 Magnetron Continuity checks can only indicate an open filament or a shorted magnetron To diagnose an open filament or shorted magnetron 1 Disconnect the high voltage lead wires from the magnetron input terminals 2 Check the continuity across th...

Страница 16: ... and magne tron on elemtextto determine if the inverter power supply is still functioning HEAT SINK RECTIFIER BRIDGE CHOKE COIL SAND BAR RESISTOR CURRENT TRANSFORMER HIGH VOLTAGE TRANSFORMER PRESET VOLUME DO NOT ADJUST FILM CAPACITORS HIGH VOLTAGE DIODES HIGH VOLTAGE CAPACITORS CN 702 CN 701 CONTROL BOARD WITH CUSTOM IC PHOTOCOUPLER DANGER HIGH VOLTAGE AND TEMPERATURE HOT LIVE HEAT SINK HIGH VOLTA...

Страница 17: ...ed Completely tighten the screws holding the door hook assembly to the oven assembly 4 Reconnect the short switch primary switch and sec ondary latch switches and check the continuity of the monitor circuit and latch switches by following the component test procedures on elemtext 11 2 Measurement of microwave output The output power of the magnetron can be determined by performing the IEC standard...

Страница 18: ...y of these components when both legs are soldered into the board may result in a false reading or damage to your meter 6 When disconnecting a plastic connector from a terminal you must hold the plastic connector and not the lead wire otherwise the lead wire may become open circuit 7 Do not touch components on the digital programmer circuit this circuit is sensitive to static electricity 8 When wor...

Страница 19: ...t including the mag netron filament circuit NOTE A large contact resistance lowers the magnetron filament volt age reducing the magnetron output or causing intermittent operation 3 Defective high voltage component Inverter circuit or Magnetron 4 Open or loose wiring of power relay RY1 5 Defective primary latch switch 6 Defective power relay RY1 or DPC AU or DPC DU Adjust door and latch switches Ch...

Страница 20: ...ere is no microwave oscil lation Symptom Cause Correction 1 Microwave output is low Oven takes a long time to cook food 1 Decrease in power source volt age 2 Open or loose wiring of magne tron filament circuit causing inter mittent oscillation 3 Ageing of magnetron Consult electrician Refer to output test procedures Change magnetron 2 Loud Buzzing noise can be heard 1 Loose fan or fan motor 3 Turn...

Страница 21: ...ot oscillate H97 H98 appears in the display window Check magnetron filament continuity Check Inverter input AC voltages at CN702 Check Inverter control signal at CN701 Pin 1 and 2 Magnetron DPC board Power relay Loose relay wiring Latch switch DPC board H V Inverter NOTE DANGER HIGH VOLTAGE Open 0V 0V Unplug CN702 and test for 3 VAC acorss the lead wire connector AC 240V Approx AC 3V Unplug CN702 ...

Страница 22: ...V line Abnormal 0V IC10 Normal 12V Step 3 3 IC 1 pin 73 Emitter of Q10 Abnormal ZB10 Q10 Ribbon cable Normal 5V Step 4 4 IC 1 pin 27 pin 15 of IC220 Abnormal IC 220 Normal IC1 CX1 NOTE The procedure for repairing the fuse pattern on the DPC is as follows 1 Fuse pattern PF2 open circuit a Remove the jumper wire PF2 b Move the jumper wire PF3 into the postion of PF2 and solder inplace Replace the DP...

Страница 23: ...the following test 1 Unplug CN702 connec tor and measure the voltage between the terminlas Abnormal 1 Latch switch 2 DPC Power relay Normal Step 2 2 Unplug CN703 connec tor and measure the voltage at Pin 1 Abnormal DPC Normal 1 Magnetron 2 Inverter circuit Diode Transistor Digital transistor A C C C C B B E E E E B B A K K Forward Forward Forward Forward Reverse Reverse Reverse Reverse A K B E E B...

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