Receiver Path - LG KS20 Operating Instructions Manual

4. TROUBLE SHOOTING

4.17 Receiver Path

MSM7200 EAR1_OP, EAR1_ON → R103, R104 → Analog Switch(U400) → R421, R420 →
CN400 → CN602 → R751, R750 → L703, L702 → CN701 → Speaker
Connect the phone to network
LGE Internal Use Only
Start
Equipment and setup call
Setup 1KHz tone out
Can you hear the tone?
NO
Sine wave appears at
R103, R104?
YES
The sine wave appears at
SPK+?
YES
The sine wave appears at
SPKR_N,SPKR_P SUB PCB
NO
The sine wave appears at
Pin 4, 1 CN400?
NO
Check an U100 SMT status
by X-ray
Exchange U100 or
Change the Main board
And Retest
YES
END
NO
Change the Main board
NO
Change the Main board
YES
Change speaker
YES
Check SUB PCB.
Check CN602
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Only for training and service purposes