Speaker Phone Path - LG U370 Service Manual

4.16 Speaker phone path

MSM6245 LINE_P,LINE_N → C405,C406, R408,R410 → Audio AMP(U403)
→ Analog Switch(U401) → Speaker
Connect the phone to network
Equipment and setup call Setup
1KHz tone out and insert
headset
Can you hear the tone?
Sine wave appears
at C405,C406 and
R408,R410
SPK_AMP_EN is 2.6V
* Pulse signal appears at
SPK+ , SPK -
* Pulse signal appears at
SPK_RCV+ , SPK_RCV- ?
Change the Main board
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Only for training and service purposes
Start
YES
NO
NO
YES
NO
YES
NO
YES
YES
NO
4. TROUBLE SHOOTING
* U370 use Class-D Amplifier.
So, The Output Signal of Amplifier was seen
Rectangular Pulse wave not sine wave.
When you inspect Main board.
Donít be cofused about that.
It was characteristic of Class-D Amplifier.
END
Change the Main Board
Change the Main Board
Change audio amp( U401)
Change Speaker
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LGE Internal Use Only