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LG LDC22720 Series, Service Manual

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LG LDC22720 Series Service Manual Download Page 20

7-2 PCB FUNCTION

7-2-1 Power Circuit

The secondary part of the TRANSFORMER is composed of the power supply for the display, the BLDC FAN Motor drive
(15.5 V), the relay drive (12 Vdc) and the MICOM and IC (5 Vdc).

The voltage for each part is as follows:

VA1 is a part for preventing over voltage and noise. When 385V or higher power is applied, the inside elements are short-
circuited and broken, resulting in blowout of the fuse in order to protect the elements of the secondary part of the
TRANSFORMER.

- 20 -

PART

VA 1

CE 3

CE 4

CE 5

VOLTAGE

115 Vac

12 Vdc

15.5 Vdc

5 V

Summary of Contents for LDC22720 Series

Page 1: ...CAUTION BEFORE SERVICING THE UNIT READ THE SAFETY PRECAUTIONS IN THIS MANUAL REFRIGERATOR SERVICE MANUAL MODELS LDC22720 ...

Page 2: ... a qualified technician Sealed system repair must be performed by a CFC certified technician SAFETY PRECAUTIONS 1 SPECIFICATIONS 2 PARTS IDENTIFICATION 3 DISASSEMBLY 3 1 Door 3 2 Door switch 3 3 Fan and fan motor 3 4 Defrost control assembly 3 5 Lamp 3 6 Control Box Refrigerator 3 7 Multi Duct 4 ADJUSTMENT 4 1 Compressor 4 2 PTC Starter 4 3 OLP Overload Protector 4 4 To remove the cover PTC 5 CIRC...

Page 3: ...40W blue TRAY MEAT YES SHELF 4EA FIXED MAGIC CRISPER NO LAMP YES 2 40W blue GUIDE BOTTLE NO DOOR COOOLING NO TRAY VEGETABLE Auto close ICE TRAY BANK SHELF SPECIFICATIONS FREEZER REFRIGERATOR CAPACITY GENERAL FEATURES I B 1EA BASKET DOOR 2 1 3 2 2 3 1full REFRIGERANT MODELS WIRE 1 LDC22720 22CUFT R134a 115 3 ...

Page 4: ... models The refrigerator you have purchased may have some or all of the items listed below The locations of the features shown below may not match your model G H I J K M N L O P Q R A B C D E F G H J L N O P K M I Q R Ice Tray Inside of H Optibin Crisper Keeps fruits and vegetable fresh and crisper Chef Fresh Snack Pan Can Dispenser Temperature Control Shelves Refrigerator Light Digital Sensor Con...

Page 5: ...NOTE This guide covers several different models The refrigerator you have purchased may have some or all of the items listed below The locations of the features shown below may not match your model G H I J K M N L O Ice Tray Inside of F Optibin Crisper Keeps fruits and vegetable fresh and crisper Chef Fresh Snack Pan Shelves Refrigerator Light Digital Sensor Control Dairy Bin Design A Door Customc...

Page 6: ... Door 1 Loosen the hexagonal bolts attaching the lower hinge to the body to remove the refrigerator door only 2 Pull out the door gasket to remove from the door foam assembly 3 2 DOOR SWITCH 1 To remove the door switch pry it out with a slotted type driver as shown in Figure 4 2 Disconnect the lead wire from the switch 3 DISASSEMBLY 6 BOLT HINGE HINGE COVER Figure 1 GASKET Figure 2 LOWER HINGE BOL...

Page 7: ...cord from the outlet 2 Remove refrigerator shelves 3 Release the hooks on both ends of the lamp shield and pull the shield downward to remove it 4 Turn the lamp counterclockwise 5 Assemble in reverse order of disassembly Replacement bulb must be the same specification as the original Max 40 W 2EA 3 5 2 Freezer Compartment Lamp 1 Unplug refrigerator or disconnect power 2 Reach behind light shield t...

Page 8: ...t flow to both the start winding and main winding 4 2 3 PTC Applied Circuit Diagram Starting Method for the Motor 4 2 4 Motor Restarting and PTC Cooling 1 It requires approximately 5 minutes for the pressure to equalize before the compressor can restart 2 The PTC device generates heat during operation Therefore it must be allowed to cool before the compressor can restart 4 2 5 Relation of PTC Star...

Page 9: ...THE COVER PTC 9 Part Customer part number Lot code date code 330 FBYY S1 BOX98 12345678 Physical termination part number Electrical characteristics part number No Name Base phenolic UL 94 V 0 rated Movable arm support plated steel Stationary contact support plated steel Heater support plated steel Heater resistance alloy Disc thermostatic alloy Movable arm spring temper copper alloy Contact movabl...

Page 10: ... CON3 GN WH 1 98 C FUSE M I MAKER W VALVE BK V S W Cr RD PK 2 2 CAPACITOR PART CAPACITOR PART CON6 1 BL 2 1 RD BK 5 5 6 6 4 4 3 3 PTC STARTER Cs BL COMP ACCESSORIES POWER PK PINK YL YELLOW BK BLACK GN GREEN BN BROWN PWB PCB ASSEMBLY ICE MAKER WH WHITE BL FUSE M BL B A HEATER SHEATH BO RD 72 C nc BK OLP YL S GN PART PART S GN YL M COMP EARTH COMP EARTH GN GN BL PR F LAMP nc R LAMPS D C BL nc PR PUR...

Page 11: ... that power supply needs to be checked by an electrician Replace Compressor Supply voltage rating with 10 Applied voltage isn t in range of Rating Voltage 10 Remove PTC Starter from Compressor and measure voltage between Terminal C of Compressor and Terminals 5 or 6 of PTC Check resistance between M C S C and M S in Motor Compressor Check resistance of two terminals in PTC Starter Check resistance...

Page 12: ...sure resistance between No 5 and 6 of PTC Starter with a Tester Figure 14 Separate OLP from Compressor and check resistance value between two terminals of OLP with a Tester Figure 15 Observation value is 115V 60Hz 6 8 30 The resistance value is 0 short or open Check another electric component Replace OLP Replace PTC Starter Figure 14 Figure 15 ...

Page 13: ...apacity Replace indicated component Advise customer that the Power supply needs to be checked by an electrician Replace indicated component Cause Check voltage at starting devices Check current flowing in sub coil of Compressor Check rating of OLP Fan motor doesn t run Heavy frost buildup on EVAPORATOR Wire is open or shorted Coil is shorted or open Open Open Replace Defrost Heater Replace indicat...

Page 14: ...e high Is there a gap in the door gasket Is the unit positioned in a firm and even place Are any unnecessary objects placed in the back side of the unit Check if the Drip Tray is not firmly fixed Check if the cover of the compressor enclosure in the lower front side is taken out Check if the door gasket is dirty with an item like juice Is the refrigerator level Is there too much food in the refrig...

Page 15: ...ing sound of refrigerant A little higher Normal discharging of the CLOG compartment and is heard and frost forms than ambient refrigerant Refrigerator don t in inlet only temperature The capillary tube is faulty cool normally WHOLE Freezer Flowing sound of refrigerant Equal to ambient Normal discharging of the CLOG compartment and is not heard and frost isn t temperature Refrigerant Refrigerator d...

Page 16: ...u need to press the ICE PLUS key and the LED will turn ON This function will remain activated for 24 hrs The first three hours the compressor and ICE PLUS will be ON The next 21 hours the freezer will be controlled at the lowest temperature After 24 hours or if the ICE PLUS key is pressed again the freezer will return to its previous temperature 5 For the first three hours notice the following cas...

Page 17: ...n t function if its sensor is defective wires are cut or short circuited 7 1 8 Electrical Parts Are Turned On Sequentially Electrical parts such as COMP defrosting heater freezer FAN etc Are turned on in the following order to prevent noise and parts damage Several parts are started at the same time at initial power on and are turned off together when TEST is completed Closed Open Closed Open Clos...

Page 18: ...frigerator sensor Failure of defrost sensor Poor of defrost Cut or short circuit wire Cut or short circuit wire Cut or short circuit wire Inspect Connecting wires on each sensor Snapping of defrost heater or Temperature fuse pull out of Connector indicated minimum 2 Hours after failure occurs All off All off All off All off LED OFF LED ON 1 hours later after starting defrost If sensor doesn t be o...

Page 19: ...NTS REMARKS TEST1 TEST2 Reset Push ICEPLUS key and ADJUST key of Freezer temperature at the same time over 3 seconds Or press TEST S W one time in the Main PCB board Push ICEPLUS key and ADJUST key of Freezer temperature at the same time over 3 seconds being in TEST MODE1 Or press TEST S W one time being in TEST MODE 1 Push ICEPLUS key and ADJUST key of Freezer temperature at the same time over 3 ...

Page 20: ... and the MICOM and IC 5 Vdc The voltage for each part is as follows VA1 is a part for preventing over voltage and noise When 385V or higher power is applied the inside elements are short circuited and broken resulting in blowout of the fuse in order to protect the elements of the secondary part of the TRANSFORMER 20 PART VA 1 CE 3 CE 4 CE 5 VOLTAGE 115 Vac 12 Vdc 15 5 Vdc 5 V ...

Page 21: ...ot work 7 2 3 Reset Circuit The RESET circuit allows all the functions to start at the initial conditions by initializing various parts including the RAM inside the MICOM IC1 when the power is initially supplied or the power supply to the MICOM is restored after a momentary power failure For the initial 10ms of power supply LOW voltage is applied to the MICOM RESET terminal During a normal operati...

Page 22: ...rt part MOTOR OFF 2V or less 0V 5V MOTOR ON 13V 15V 0V 2V 3V a b c NO 12 1 This circuit makes standby power 0 by cutting off power supplied to Iss inside of the fan motor in the fan motor OFF 2 This is a circuit to perform a temporary change of speed for the fan motor and applies SC voltage up to 7 5V 16V to motor 3 This circuit prevents over driving the fan motor by cutting off power applied to t...

Page 23: ...splay is pushed Alarm for open door beep beep beep 2 2 Cooling motor driving circuit machine room 1 This circuit makes standby power 0 by cutting off power supplied to Iss inside of the fan motor in the fan motor OFF 2 This circuit prevents over driving the fan motor by cutting off power applied to the fan motor in the lock of fan motor by sensing the operation RPM of the fan motor part part MOTOR...

Page 24: ...perature into MICOM OPENING or SHORT state of each TEMPERATURE SENSOR are as follows 24 SENSOR CHECK POINT NORMAL 30 C 50 C SHORT CIRCUITED OPEN Freezer Sensor POINT Voltage Refrigerator Sensor POINT Voltage 0 5 V 4 5 V 0 V 5 V Defrosting Sensor POINT Voltage A B C 4 Open Door Detection Circuit Check Closed 5 V Open 0 V Freezer Refrigerator Door Measurement Location Pin No 15 Freezer Door Pin No 1...

Page 25: ...tepping Motor Damper Circuit The circuit shown below is the damper circuit to regulate the refrigerator temperature 25 7 2 7 Temperature Compensation Overcooling Undercooling Compensation Circuit 1 Refrigerator Temperature Compensation ...

Page 26: ...circuit shown below determines whether a function control key on the operation display is pushed It also tu rns on the corresponding function indication LED LED Module SEVEN SEGMENT DISPLAY SEVEN SEGMENT DISPLA Y MODULE The drive type is the scan type 26 ...

Page 27: ...OM SENSOR 20 C 22 3 K 77 K 15 C 16 9 K 60 K 10 C 13 0 K 47 3 K 5 C 10 1 K 38 4 K 0 C 7 8 K 30 K 5 C 6 2 K 24 1 K 10 C 4 9 K 19 5 K 15 C 3 9 K 15 9 K 20 C 3 1 K 13 K 25 C 2 5 K 11 K 30 C 2 0 K 8 9 K 40 C 1 4 K 6 2 K 50 C 0 8 K 4 3 K The resistance of the SENSOR has a 5 common difference Measure the resistance of the SENSOR after leaving it for over 3 minutes in the measuring temperature This delay ...

Page 28: ...r compressor shuts off COMPRESSOR RELAY is Replace MAIN PWB donÕt press the KEY and poor wait THE CONNECTING WIRE Check the connection of the is poor black wire of the MAIN PWB CONNECTOR CON2 2 If refrigerant is leaking Measure the amount of frost Refrigerant leakage Replace the leaking part and sticking on EVAPORATOR replace any lost refrigerant and the surface temperature of the condenser pipe F...

Page 29: ...liner damaged Replace Door liner door is closed DEFROSTING is NO DEFROSTING 1 If HEATER emits heat USE TEST MODE2 HEATER disconnection Replace HEATER poor forced DEFROSTING TEMPERATURE FUSE Replace TEMPERATURE disconnection FUSE Connection is poor Check EVAPORATOR connection and wire of MAIN PWB CONNECTOR DEFROST SENSOR is poor Replace DEFROST SENSOR HEATER RELAY is poor Replace Ry2 of MAIN PWB 2 ...

Page 30: ...7 5 MAIN PWB ASSEMBLY AND PARTS LIST 7 5 1 Main PWB Assembly 30 ...

Page 31: ...7 5 2 Replacement Parts List 31 ...

Page 32: ...7 5 3 PWB Assembly Display and Parts List 32 SW106 Best Model ...

Page 33: ...7 6 PWB DIAGRAM 7 6 1 PWB Main Assembly 33 ...

Page 34: ... 34 ...

Page 35: ...C 305C 105F 323B 329C 420A 319A 319C 503D 282B 282H 410A 406B 409D 503F 120B 409B 158A 332A 135C 158E 145B 409B 503C 503E 106A 145A 282F 903D 610A 903E 610A CASE PARTS CAUTION Use the part number to order part not the position number B01 106B 903A 903B 903B 103C 503G B01 S22 S01 328A 8 EXPLODED VIEW REPLACEMENT PARTS LIST 125D 327A 405A 405C 405F 319E 329A 404A 405G 410G 128E 128F 619B S38 35 EV 4...

Page 36: ...FREEZER PARTS CAUTION Use the part number to order part not the position number 136A 237C 136B 248E 248F 131A 145C 145F 36 EV ...

Page 37: ... the part number to order part not the position number 37 EV 143E S24 S24 143E 143E 140D 140E 140D S24 140D 140B 140B 140E 140B 140E 140B 142D 143F 142E S24 128B 128A 170A 167B 154A 155B 151A 151C 151A 103E 103E S24 S24 S24 S24 S24 ...

Page 38: ...e part number to order part not the position number 233A 230A 231A 241A 241B 241E 241C 241D 243A S27 286A 286A 212G 244E 212J 250A 205B 205C 203A 200A 201A 212J 38 EV 249A 249E 250B 249J 621B 621C 250B 249B 249K 249F 244A 212A ...

Page 39: ...CAUTION Use the part number to order part not the position number 627A 616E 622B 618A 623C EV S29 ICE MAKER PARTS 602A 600A S28 39 600C 619C S31 619A 262D ...

Page 40: ...or Electric Appliance Film Box 167B 4890JL1002H Shelf Glass 411A 6411JK1006A Power Cord Assembly 170A 3391JJ2004H Tray Assembly Meat 412D 6877JK2011B Drawing Assembly 200A 3581JJ8715K Door Assembly Freezer 418A 5300JB1100J Heater Sheath 201A ADD55908401 Door Foam Assembly Freezer 420A 4681JB1029J Motor DC 203A 4987JJ1004Z Gasket Assembly Door 501A EBR41531303 PCB Assembly Main 205B 5006JJ2014A CAP...

Page 41: ...or Electric Appliance Film Box 167B 4890JL1002H Shelf Glass 411A 6411JK1006A Power Cord Assembly 170A 3391JJ2004H Tray Assembly Meat 412D 6877JK2011B Drawing Assembly 200A 3581JJ8715M Door Assembly Freezer 418A 5300JB1100J Heater Sheath 201A ADD55908403 Door Foam Assembly Freezer 420A 4681JB1029J Motor DC 203A 4987JJ1004A Gasket Assembly Door 501A EBR41531303 PCB Assembly Main 205B 5006JJ2014A CAP...

Page 42: ...or Electric Appliance Film Box 167B 4890JL1002H Shelf Glass 411A 6411JK1006A Power Cord Assembly 170A 3391JJ2004H Tray Assembly Meat 412D 6877JK2011B Drawing Assembly 200A 3581JJ8715L Door Assembly Freezer 418A 5300JB1100J Heater Sheath 201A ADD55908402 Door Foam Assembly Freezer 420A 4681JB1029J Motor DC 203A 4987JJ1004Z Gasket Assembly Door 501A EBR41531303 PCB Assembly Main 205B 5006JJ2014A CAP...

Page 43: ...P No MFL49482601 March 2008 ...

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