Speaker Phone Path - LG U970 Service Manual

4.19 Speaker phone path

MSM6280(U200) LINE_OP,LINE_ON → C318/R312, C319/R316 → Audio AMP(U302)
→ Analog Switch(U301) → CN601 → CN700 → CN701 → CN901 → Speaker
Connect the phone to network
equipment and setup call
Setup 1KHz tone out
C318/R312 and C319/R316?
The sine wave appears at
Start
Sine wave appears at
YES
SPK_AMP_EN(R309) is
2.6V?
YES
SPK+?
YES
The sine wave appears at
SPK_N,SPK_P LCD FPCB?
NO
The sine wave appears at
PIN28,PIN29,CN701?
NO
The sine wave appears at
PIN41,PIN42, CN601?
NO
Change the Main board
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4. TROUBLE SHOOTING
NO
Change the Main board
NO
Change the Main board
NO
Change the Main board
YES
Change speaker
YES
Check LCD FPCB.
Check CN901
YES
Check KEY FPCB.
Check CN700