No Sound - LG CJ65 Service Manual

NO SOUND

There is no sound output by DIGITAL AUDIO AMP DAMAGE, repair the set according to the following
guide.
5-2. BY DIGITAL AUDIO AMP DAMAGE (IN ALL FUNCTIONS)
5-2-1. Solution
Please check and replace C744(IC701), C746(IC702) on MAIN board.
5-2-2. How to troubleshoot (Countermeasure)
1) Check PWM_FL±, PWM_FR± & PWM_SW± signals from IC700 to IC701 & 702 each input function.
  If no signal, check if I2S audio signals are entered to IC700.
Refer to "I2S audio signal interface" on Item 5-1.
2) Check PVDD.
  If PVDD is abnormal, check the SMPS.
3) Check +12 V for driving the gate of AMP IC.
a. All the powers are normal, but if +12 V is low, there is possible for AMP IC to be damaged.
b. Remove C742, C746(IC702), C740, C744(IC701) one by one.
When removed a inductance, if +12 V is recovered, the IC connected to it was damaged.
c. Replace the IC with a new one.
4) Check the impedance between IC701/IC702_OUT_A/OUT_B/OUT_C/OUT_D & GND.
a. If the impedance is 0 Ω, the IC must be damaged.
b. After removing the heat sink, replace it with a new one.
5-2-3. Service hint (Any picture / Remark)
ONE POINT REPAIR GUIDE
< Signal check point >
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