LG KU250 Service Manual - Page 76
Checking VC-TCXO Block
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4. TROUBLE SHOOTING 4.4 Checking VC-TCXO Block The reference frequency (19.2MHz) from X100 (VC-TCXO) is used in UMTS TX part, GSM part and BB part. TP1 VREG_TCXO_2.85V TCXO X100 DSA321SCE-19.2M 7 NC3 8 NC4 NC2 6 NC1 5 3 OUTPUT GND 2 VCC VCONT 4 1 19.2MHz 100ohm R124 TRK_LO_ADJ TP2 C181 0.1u C182 1000p 0.01u C183 VREG_BT_2.85V TP4 TCXO_PM RTR6275_TCXO C185 100p C187 1000p TP3 R128 100K C188 0.01u VCC 5 2 4 U104 3 TC7SH04FU GND Schematic of the VC-TCXO Block C186 1000p TCXO_BT TP3 TP4 TP2 TP1 Test Point of the VC-TCXO Block - 77 -
4. TROUBLE SHOOTING
- 77 -
4.4 Checking VC-TCXO Block
The reference frequency (19.2MHz) from X100 (VC-TCXO) is used in UMTS
TX part, GSM part and BB part.
TCXO
2
4
VCC
5
TC7SH04FU
U104
GND
3
100p
C185
0.1u
C181
R124
100ohm
1000p
C182
R128
100K
C183
0.01u
1000p
C186
DSA321SCE-19.2M
X100
GND
2
5
NC1
NC2
6
7
NC3
NC4
8
OUTPUT
3
4
VCC
1
VCONT
19.2MHz
0.01u
C188
C187
1000p
VREG_TCXO_2.85V
TRK_LO_ADJ
TCXO_BT
VREG_BT_2.85V
TCXO_PM
RTR6275_TCXO
TP2
TP1
TP3
TP4
Schematic of the VC-TCXO Block
Test Point of the VC-TCXO Block
TP1
TP4
TP3
TP2