42LM760S, 42LM760T, 42LM761S, 42LM761T, 42LM765S, 42LM765T (CHASSIS:LD22E) - LG TV Service Manual (repair manual). Page 116

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Checking order when there is no audio
① Check the contact condition of or 24V connector of Main Board
② Measure the 24V input voltage supplied from Power Board
(If there is no input voltage, remove and check the connector)
③ Connect the tester RX1 to the speaker terminal and if you hear the Chik Chik sound when you touch the GND 
and output terminal, the speaker is normal. 
Standard Repair Process Detail Technical Manual
Voltage and speaker checking method 
when there is no audio
C. Audio error_No audio/Normal video
<ALL MODELS>
A25
Established 
date 
Revised 
date 
Error 
symptom
Content
LCD  TV
24 Pin
 
(Power Board ↔ Main Board)
SMAW200-H24S (YEONHO)
1
Power on
2
20V (24V)
3
20V (24V)
4
20V (24V)
5
GND
6
GND
7
GND
8
GND
9
3.5V
10
3.5V
11
3.5V
12
3.5V
13
GND
14
GND
15
GND
16
GND
17
12V
18
Inverter On/off
19
12V
20
Lamp : A-Dim
LED : N.C
21
12V
22
PWM Dim #1
23
GND/P_DIM2
24
Error-out
2010. 12 .14
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