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Samsung RS21**** - Service Manual
 
Identifying the Correct Model (sticker on lower left hand side of appliance)
 
 
Circuit Diagrams
 
 
bulletWhen the Freezer Door is opened the switch activates points 1 & 2, and 5V is supplied with the following circuit:-
bulletCN30 Pin 9 ? Freezer Door Switch ? CN30 Pin 1 ? R408(10K?) ? MICOM port 43
bulletWhen the Refrigerator Door is opened the switch activates points 1 & 2, and 5V is supplied with the following circuit:-
bulletCN30 Pin 10 ? Refrigerator Door Switch ? CN30 Pin 5 ? R407(10K?) ? MICOM port 43
bulletWhen either door is detected open by the MICOM the relevant Compartment Light is illuminated then the Fan Motor is stopped, followed by the Door Open Alarm sounding.
 
Thermistor Sensor Circuit
 
 
bulletThe Freezer Defrost Sensor is connected in parallel with a Bi-Metal and a Temperature Sensor.
bulletDuring normal operation the Bi-Metal is on, with a 0V input to the MICOM
bulletDuring the Defrost Cycle the Bi-Metal is will switch off once the temperature reaches 12°C
 
Load Drive Circuit
 
 
bulletThe Load of the system is controlled by the main PCB
bulletMost of the relays or SSRs can control the compressor; refrigerator defrost heater; freezer defrost heater and several option functions
bulletFor the compressor, pin no.18 of the microprocessor signals High (5V)
bulletThis signal enters pin no.5 of IC3 and pin no.14 of the output terminal which have the base and collector functions of IC3 turns on and connects the GND
bulletRelay (RY73) will be grounded through pin no.14 of IC. Magnetic field will generate so that the second side of RY73 is activated and 115V is supplied to the compressor. On the other hand if pin no.18 of the microprocessor turns Low(0V) - pin no.5 of the IC3 - the current RY73 relay and magnetic field will shut down in sequence. A contact point in RY73 is off, and finally the compressor will stop.
 
Damper Drive Circuit
 
 
bulletThe CoolSelect Zone Drawer is controlled by a damper that is designed to control or block the cold air
bulletFor quick cooling the damper will be closed. This will direct air to the Cool Select Zone Drawer only
bulletFor thawing the evaporator heater is ON and the damper is controlled by the refrigerator temperature
bulletThe damper is operated by a stepping motor controlled by a Driver (IC7)
bulletThe stepping motor uses 4 combined signals to open and close the damper.
 
Fan Motor (BLDC) Drive Circuit
 
 
bulletTo reduce energy consumption the refrigerator compartment and the freezer compartment utilise a BLDC motor, used to reduce energy consumption
bulletFan motors have two speeds - High and Low
bulletGenerally fan motors run at high speed during day time and low speed during night time.
 
 
Source Power Circuit
 
 
bulletThis circuit shows SMPS(Switch Mode Power Supply) which converts the 230V 50HZ AC input voltage to 320V DC voltage by way of the wave rectifier BD1
bulletThe converted DC voltage generate a constant waveform using a high speed 100KHz switching motion of TOP223Y
bulletDiode D104 will rectify the generated voltage and transform into a 12V DC source power used for the digital display panel and relays
bulletThe regulator KA7805 finally transforms this into a 5V DC source power for the control board and sensor’s circuits.
 
Diagnostics
 
The following processes are guides as to how to diagnose certain fault conditions
 
1. No Power – (Refer to Source Power Circuit for connections)
 
 
2. Compressor and cooling fan motor do not work normally (Refer to Load Circuit for connections)
 
 
3. If defrost function
 
 

4. Problem with self diagnosis

a) Ambient Sensor fault

 
 
b) Freezer/Refrigerator compartment temperature sensors
 
 

5. If Alarm Sounds

a) “Ding Dong” continuously sounds

 
 
b) “Beep” sounds continuously
 
 
c) Without sound of buzzer operation
 
 

6. If Display PCB is faulty

a) Display PCB does not illuminate, or only certain segments illuminate

 
 
7. If fan doesn’t work
 
 

Notes about Fan motor operation:

bulletUnder normal operating conditions the F-fan will operate in conjunction with the compressor. However if the CoolSelect Zone™ function is selcted the F-fan may not operate
bulletIf the door has been opened for a long period of time the BLDC fan motor will not operate until such time as the compartment temperature cools. This is too prevent the warmer air from being pushed around the system, which in turn could cause icing or frost build up
bulletWhen the refrigerator door is open the F-fan motor will also stop running.
 
8. If the Refrigerator/Freezer light does not illuminate
 
 
9. Solenoid in Ice-Chute cover is does not operate
 
 
10. If Crushed Ice/Cubed Ice not working properly
 
 
Ref.1) Check Sensors
 
 
Disconnect the relevant connector from the Main PCB, to measure sensor resistances.
1. Check Freezer Sensor resistance between pins no.2 and 3 of CN30
2. Check Fridge Sensor resistance between pins no.6 and 7 of CN30
3. Check F-Defrost Sensor resistance between pins no.2 and 4 of CN30
4. Check R-Defrost Sensor resistance between pins no.6 and 8 of CN30
5. Check Ambient Air Sensor resistance between pins no.1 and 4 of CN31
6. Check Ice Maker Sensor resistance between pins no.3 and 4 of CN90
7. Check CoolSelect Zone™ Sensor resistance between pins no.1 and 4 of CN51
8. Compare resistances with the following table to determine the actual temperature. If the resistance reading is either or check wiring or connector connections.
 
 
Ref.2) Check Door Switch
 
 
The door switch is a double pole switch, one detects Door open/close (measuring 5V at the PCB), the other side turns the on/off the compartment light.

Refrigerator/Freezer Room Light

1. Check operation of light by activating/de-activating light switch – If light does not illuminate check switch

Main PCB sensor for opening of Refrigerator door

1. Check voltage across pin no.s 5 & 10 of CN30
2. When door is open 5VDC should be read
3. When door is closed 0VDC should be read

Main PCB sensor for opening of Freezer door

1. Check voltage across pin no.s 1 & 9 of CN30
2 . When door is open 5VDC should be read
3 . When door is closed 0VDC should be read

 
Circuit Diagram for Basic Models
 
 
Circuit Diagram for Dispenser Models
 
 
Circuit Diagram for Dispenser & Cool Select Zone™ Models
 
 
Circuit Diagram for Home Bar & Dispenser Models
 
 
Circuit Diagram for Home Bar & Dispenser Cool Select Zone™ Models
 
 

 

 
 
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© British Gas 2007