Speaker Phone Path - LG KS20 Operating Instructions Manual

4. TROUBLE SHOOTING

4.19 Speaker phone path

MSM7200 LINE_OP,LINE_ON → C402/R403, C401/R402 → Speaker AMP(U401) → Analog
Switch(U400) → R421, R420 → CN400 → CN602 → R751, R750 L703, L702 → CN701 →
Speaker
Connect the phone to network
equipment and setup call
Setup 1KHz tone out
Check an U100 SMT status
by X-ray
Exchange U100 or
Change the Main board
And Retest
LGE Internal Use Only
Start
Sine wave appears at
C402/R403 and C401/R402?
YES
nSPEAKER_SHDN(TP400) is
2.6V?
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
- 128 -
NO
Change the Main board
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