Micom Circuit Description; Description Of Pwb Circuit - LG GR-B197WVS Service Manual

MICOM CIRCUIT DESCRIPTION

1. Description of PWB Circuit

1-1. Power Circuit
1. GR-P247, GR-P207, GR-L247, GR-L207, GR-L197
Power circuit is composed of switching mode power supply (SMPS) electric parts. SMPS is composed of rectifying part
(D1~D4, CE1) which converts AC to DC voltage, switching part (IC2) which switches this converted DC voltage, trans which
transmits primary energy to secondary energy, secondary power source which transmits power to MICOM and IC, and feed
back part (IC3, ZD1) which feeds back voltage to primary trans in order to maintain constant secondary voltage.
The voltages at each part are as follows.
Note : If circuit is abnormal, repair it after 3 minutes when power cord is unplugged. Be care of electric shock as high
voltage (DC 310 V) is applied to the circuit.
2. GR-C247, GR-C207, GR-B247, GR-B207
In the trans secondary side is composed of power source (12 Vdc) for driving relay and power source (5 Vdc) which
supplies power to MICOM and IC. Voltages in each part are as follows.
Position VA1 CM1 CM2 CE2 CE4
Voltage 220 Vac 14 Vac 17 Vac 12 Vdc 5 Vdc
1-2. Oscillation Circuit
This is to generate basic time for synchronous clock and time calculation for
internal logic element to send and receive information.Standard parts should be
used as the time calculated by IC1 shall be changed or shall not work if OSC1
specification is changed.
1-3. Reset Circuit
Reset circuit is to initialize RAM in MICOM (IC1) and make all functions
to start from the initial conditions when power is nitially applied or
power is reapplied to MICOM after power cut. Low voltage is applied
for 10 ms to the reset terminal of MICOM when power is applied. 5
voltage is applied to the reset terminal for general operation. (MICOM
does not work when IC9(Reset IC) is failed)
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