Pwm Modulation Check - LG FB165DAB Service Manual

ELECTRICAL TROUBLESHOOTING GUIDE

8. PWM MODULATION CHECK

PWM modulation
part check
Check
CN700 Pin1
5 V.
YES
Check IC701(PS9851)
VDD Pin voltage(16,24,29,32,35,40,48).
Check X601 Pin2: 3.3 V.
YES
Check
X700 19.2 MHz
operation.
YES
Check IC701 Pin51 CLK input.
YES
IC101
Pin38: PWM RESET
Pin85: PWM SDA
Pin84: PWM SCL
output
YES
Check
IC701(PS9851) data input
Pin14 PWM wave.
YES
Check
PWM modulator output
FL:Pin27(+),28(-) FR:Pin30(+),31(-)
other output
YES
OK
NO
Refer to
SMPS troubleshooting.
NO
Replace IC703.
NO
Replace X601.
Check
NO
line resistor output
SDA: R153, SCL: R155,
RST: R131.
OK
Check
NO
IC500 DVD MPEG
I2S output.
OK
NO
Check
IC701(PS9851).
OK
3-35
NO
YES
NO
YES
NO
YES
Replace related resistor.
Replace IC500.
Replace IC701.