Checking Vcxo Block - LG CU400 Service Manual

4. TROUBLE SHOOTING

4.2 Checking VCXO Block

The reference frequency (19.2MHz) from X100 (TCXO) is used in UMTS TX part, GSM part
and BB part.
Check 1. Crystal part
If you already check this crystal part, you can skip check 1.
TP1
TCXO_PM
RTR6275_TCXO
RFR6275_TCXO
LGE Internal Use Only
VREG_TCXO_2.85V TCXO
4
VCC VCONT
3
OUT
TG-5010LH_19_2M
X100
19.2MHz
TP4
C137 0.01u
C140 1000p
C144 1000p
TP3
C147 1000p
U104
TC7S04FU
Schematic of the Crystal Part
TP3
TP1
Test Point (Crystal Part)
- 66 -
R118
100ohm
1
TRK_LO_ADJ
2
GND
TP2
R124 100K
C145
1000p
VCC
5
2 4
TCXO_BT
3
GND
TP4
TP2
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