LG MAX220UB Service Manual page 15

CAUTION - Tip for repair
Before exchange power amp IC(TB2931) for no audio problem, you have to check
below list.
1. Check VCC (pin 20, 6) & GND
2. Check input pin 11, 12, 14, 15
3. Check Standby, pin 4
: Follow the below list.
4. Check Mute function, pin 22
: Follow the below list.
Stand-by Power
ON OFF
OFF ON
5. Check Ripple pin 10.
: Normally it is high (about 10 V)
Mute Sound
ON OFF
OFF ON
6. Re-soldering all the pin of IC.
: Prevent crack of solder line.
* Keep changed IC, We request that you send it to HQ.
Sound Voltage
OFF 0 to 1.0
ON 2.2 to VCC
Voltage
0 to 1.0
2.2 to VCC
10
Ripple
C1
IN1
11
C1
IN2
12
13 Pre-GND
C1
IN3
15
C6
16 AC-GND
C1
IN4
14
5 V
4 Stby
Play
R1
Mute
22 Mute
Picture 1) Power IC desc.
2-6
1 6 20
TAB V V
CC2 CC1
Out1 (+)
9
PW-GND1
8
Out1 (−)
7
Out2 (+)
5
PW-GND2
2
Out2 (−)
3
Out3 (+)
17
PW-GND3
18
Out3 (−)
19
Out4 (+)
21
PW-GND4
24
Out4 (−)
23
25
Offset/short
+B
R
L
R
L
R
L
R
L