NN-CF770M 4 DESCRIPTION OF OPERATING SEQUENCE 4.1. Variable power cooking 4.3. Auto Menu cooking control When the Auto Menu feature is selected and the [Start] button is tapped: High Voltage Inverter Power Supply (U) controls output power 1. The digital programer circuit determines the power level and by the signal from Digital Programmer Circuit (D.P.C.).
NN-CF770M 4.6. Convection cooking control The digital programmer circuit controls the ON-OFF time of the heater in order to control oven cavity temperature. 1. After selecting desired oven cavity temperature Convection/Grill Convection (the range of selected oven temp is 100°C-250°C) and pressing [Start] button, a high level signal comes out of the micro computer and applies to power relay (RY6).
NN-CF770M 5 CAUTIONS TO BE OBSERVED WHEN TROUBLESHOOTING Unlike many other appliances, the microwave oven is a high voltage, high current device. It is free from danger in ordinary use, though extreme care should be taken during repair. CAUTION Servicemen should remove their watches & rings whenever working close to or replacing the magnetron.
NN-CF770M 5.6. Verification after repair Discharging the high voltage capacitors WARNING 1. After repair or replacement of parts, make sure that the There is high voltage present with high current capabilities screws of the oven, etc. are neither loosen or missing. in the circuits of the primary and secondary windings, choke Microwave energy might leak if screws are not properly coil and heat sinkof the inverter.
NN-CF770M 6.3. Digital programmer circuit 6.2. Magnetron (D.P.C) & Membrane Sheet 1. Steps same as disassembly of H.V. Inverter step 1 to step NOTE: 2. Remove 1 screw holding thermistor on magnetron. Be sure to ground any static electric charge built up on your body before handling the D.P.C.
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NN-CF770M 3. Remove 2 screws holding D.P.C. board DU (Relay board). 6. Separate D.P.C board from tabs on the escutcheon base and remove D.P.C board. To replace membrane key board 7. Use tools such as kinfe etc. to lift the edge of membrane sheet and peel off escutcheon sheet &...
NN-CF770M 6.4. Low voltage transformer 6.5. Fan motor and/or power relays (RY1, 1. Disconnect 2 lead wires from fan motor terminals. RY2, RY4, RY5, RY6, RY7) 2. Remove 4 screws holding inverter reinforcement bracket A on right heater panel & base plate respectively. NOTE: Be sure to ground any static electric charge built up on your body before handling the D.P.C.
NN-CF770M 6.7. Door assembly 6.6. Quartz heater 1. Remove door C from door E by carefully pulling outward, 1. Disconnect lead wires from heater terminals. starting from upper right hand corner using a flat blade 2. Remove 2 screws holding heater mounting plate from the screwdriver.
NN-CF770M 6.8. Stirrer motor 1. Remove the motor cover by breaking off at the 8 spots indicated by arrows with a cutter or the like. 6.9. Convection fan motor and convection heater 1. Remove 1 screw holding side cover on cavity back plate. NOTE: After removing the motor cover, be sure that cut portions are properly trimmed or bent to the inside...
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NN-CF770M 4. Remove 1 screw holding back cover on the lower of back plate, then remove back cover. To replace convection heater 7. Remove 1 nut holding convection fan, then remove 5. Disconnect 2 lead wires from thermal cutout and convection convection fan.
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NN-CF770M 9. Remove 1 screw holding heater bracket A on convection inside cover A. 10. Remove 2 screws holding convection heater on convection inside cover A. To replace convection motor 11. Remove 2 screws holding convection motor on convection fan bracket.
NN-CF770M 7 COMPONENT TEST PROCEDURE 7.3. Magnetron WARNING 1. High voltage is present at the output terminals of the High Voltage Inverter (U) including aluminum heat sink during any cook cycle. Continuity checks can only indicate an open filament or a 2.
NN-CF770M 7.4. Inverter power supply (U) 5. Program oven at High power for 1 minute and press [Start] button. DO NOT try to REPAIR H.V. Inverter power supply a. After approximately 3 seconds, oven stops operating. (U).Replace complete H.V. Inverter(U) Unit. b.
NN-CF770M 8 MEASUREMENTS AND ADJUSTMENTS 8.1. Adjustment of primary latch switch, secondary latch switch and monitor interlock switch. 1. Mount the Primary latch switch, the Secondary latch switch and the Monitor interlock switch to the door hook assembly as shown in illustration. NOTE: 8.2.
NN-CF770M 9 PROCEDURE FOR MEASURING MICROWAVE ENERGY LEAKAGE 9.2.1. Measurement with the outer panel removed. Whenever you replace the magnetron, measure for radiation leakage before the outer panel is installed and after all necessary components are replaced or adjusted. Special care should be taken in measuring around the magnetron.
NN-CF770M 10 TROUBLESHOOTING GUIDE DANGER: 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 equipment because this circuit generates very large current and high voltage. Operating a misaligned inverter circuit is dangerous. 2.
NN-CF770M 10.1. (Troubleshooting) Oven stops operation during cooking SYMPTOM CAUSE CORRECTIONS 1. Oven stops in 3 seconds after No input AC is supplied to H.V.Inverter (U) 1. Latch Switch pressing [Start] button. CN702 terminals 2. Power relay RY1 3. Loose lead wire connector CN701, CN702 4.
NN-CF770M 10.2. (Troubleshooting) Other problems SYMPTOM CAUSE CORRECTIONS 1. Oven is dead. 1. Open or loose lead wire harness Fuse is OK. 2. Open thermal cutout / thermistor Check thermal cutout is defective. No display and no operation at all. 3.
NN-CF770M 10.3. Troubleshooting of inverter circuit (U) and magnetron This oven is programmed with a self diagnostics failure code system which will help for troubleshooting. H95, H97, H98 and H99 are the provided failure codes to indicate magnetron and inverter circuit problem areas. This section explains failure codes of H95, H97, H98 and H99.
NN-CF770M 10.4. Trouble related to Digital Programmer Circuit SYMPTOM STEP CHECK RESULT CAUSE/CORRECTIONS No display when oven is first plugged Fuse pattern of D.P.C. Normal →Step2 Open Replace D.P.C., L.V.T. or Fuse Pattern IC10 pin4 voltage Abnormal 0V L.V.T. →Step3 Normal=18V IC1 pin9 voltage Abnormal...
NN-CF770M 10.5. SIMPLE WAY OF H.V. INVERTER/MAGNETRON TROUBLESHOOTING Purpose: 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 this procedure.
NN-CF770M 11.2. PARTS LIST NOTE: 1. When ordering replacement part(s), please use part number(s) shown in this part list. Do not use description of the part. 2. Important safety notice: Components identified by mark have special characteristics important for safety. When replacing any of these components, use only manufacture’s specified parts.
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NN-CF770M Ref. No. Part No. Part Name & Description Pcs/Set Remarks F10589M60BP SIDE COVER F40307Q70BP AIR GUIDE D F64609M50QP HEATER MOUNTING PLATE F22397Q70BP CONVECTION FAN BLADE F41594V00BP COOLING FAN BLADE F41809M60BP CONVECTION FAN BRACKET F490S9M80CP CONVECTION FAN MOTOR F631D9M80CP CONVECTION HEATER F64174V00BP HEATER BRACKET A F66797Q70BP...
NN-CF770M 11.4. DOOR ASSEMBLY Ref. No. Part No. Part Name & Description Pcs/Set Remarks F30186P40AG DOOR KEY A F302A9M50SQP DOOR A (U) F301P9M60BP DOOR E (U) F30215G10XN DOOR KEY SPRING F30859Q30AP DOOR C F04114180CP HC LABEL F02459660AP DHHS LABEL...