Samsung RL38H Series, Service Manual

Page: 185 / 206

185
5. SELF DIAGNOSIS & TROUBLE SHOOTING REFERENCE INFORMATION
9-3-1-13) Load Driving Circuit Part
1) Most loads of the electronic type refrigerator are controlled by the main PCB.
2) The compressor (F FAN(option)), the defrosting heater, and the lamps in the refrigerator are
controlled by the relay.
3) Let me explain about the defrosting heater as an example. To run the defrosting heater, the
HIGH(5V) signal comes out from the Pin no. 2 of the MICOM. This signal goes to No.
6 of IC70 as an input. The Pin no. 6 of the IC70 is operated as a base of the NPN TR and
the output terminal, Pin no.11 is operated as a collector of the TR. So, if the Pin no. 6 of the
IC70 gets 5V input, the No.11 of the IC70 is turned on and conducted to the GND. The end
of the RY74 COIL connected to the No. 11 of the IC70 becomes LOW(0V) and the power,
+12 V, on the other end of the RY74 COIL flows to the GND through No.11 of the IC70.
As magnetic lines of force (electromagnet) are generated during flowing current though the
coil, the contact of the secondary side (load side) in the RY74 is closed and then, the AC
input (220~240VAC) across the defrosting heater turns on the heater. In case that the Pin
no. 2 of the MICOM becomes LOW(0V), the Pin no. 11 of the IC70 opens (Switch off state)
and the power is off. So, the current on the relay RY74 is off, the magnetic lines
(electromagnet) are disappeared, the contact of the secondary side opens, and the
defrosting heater is off.
4) The other loads are operated in the same principle. (The compressor and the lamps in the
refrigerator compartment)
5) AC Fan motor in the refrigerator compartment is an option. The model LCD display applied
has two selections - BLDC motor or AC Fan motor. The AC Fan Motor is wired in link with
the compressor. In case that the compressor is off, the fan is off. In case that the compressor
is “on”, the fan is “on”
The equivalent circuit for the
compressor & defrosting heater
AC~
OPWER
COMPRESSOR
DEF HEATER