LG G5300 Service Manual Trouble Shooting
4. TROUBLE SHOOTING
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4. TROUBLE SHOOTING
4.1 RF Components
RF Components
Reference Description Reference Description
U401 RF Main Chipset FL402 Dual SAW Filter
CN401 Mobile S/W X401 VCTCXO
FL401 Ant. S/W U404 LDO
U402 PAM U403 Inverter IC
CN401
U402
FL401
U401
U404
X401
FL402
U413
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4. TROUBLE SHOOTING
4.2 Rx Trouble
62 CH, 7 level setting (TCH)
62 CH, - 60dBm s etting ( BCCH)
START
4. Check
Ant SW &
Mobile SW
6. Check
RX IQ
3. Check
Control
Siganl
5. Check
Saw Filter
Circuit
Now See next Page to see
How to check each parts
Redownload SW, CAL
HP8922 : Test mode
Spectrum analyzer set ting
Ocillo scop e settin g
2. Check
VCTCXO Circuit
1. Check
Regulator Circuit
RX Check Area
4. TROUBLE SHOOTING
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4-2-1 Checking Regulator Circuit
2.2u
C458
2012
C460
VBAT
470p
4
GND
2
IN
NR
5
OUT
1
_ERR
3
6
_SD
ADP3330
U404
10uF
C459
0
R430
2012
RF2.85V
VSYNTHEN
Pin 6. High ?
Yes
Changing the Boa rd
RF 2.85V O.K ?
Yes
No
Replace U404
Reg ulat or Circu it is OK
See next Page to check
VCTCXO
No
Check Pin 6.
Check Pin 1.
U404.1 U404.6
4. TROUBLE SHOOTING
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4-2-2 Checking VCTCXO Circuit
15K
R424
100
R425
1MR426
C456
1000p
IN
2
OUT
4
VCC
5
U413
SN74AHC1GU04DCKR
GND
3
X401
1
CTL
2
GND
3
OUT
VCC
4
13MHz
2012
C455
2.2u
1000p
C457
13MHZ
2V7_VTCXO
AFC
X401. 4 X401. 3
Graph 4-1. VCTCXO 13MHz Graph 4-2. VCTCXO 2.7V
4-2-3 Checking Control Signal
4. TROUBLE SHOOTING
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Graph 4-3. RF Control Signal
TP402 (LE)
LE
Data
Clock
TP404 (Clock) TP406 (Data)
TP403 (REXN)
Check TP 403.
Lev el i s Hi gh?
Yes
Control Signal is OK
See next Page to check
ANT SW & Mobile SW
No
Check TP 406, 404,
402. Check if there is
Any Ma jor Difference
Refe r to Gr aph 4-3
Similar?
Yes
No
Dow nload the SW
Dow n load the SW
4. TROUBLE SHOOTING
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4-2-4 Checking Ant SW & Mobile SW
CN401 PIN 1
CN401 PIN 2
L420
C448
C445
L409 FL401
Table 4-1. ANT SW Control Logic
L410
4. TROUBLE SHOOTING
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DCSSEL
GSMSEL
TXPA
Low
High
Low
VC1
Low
VC2
Low
Graph 4-4. ANT SW Control
GSM. DCS RX Mode
Graph 4-6. Dual Control Signal
forDes Rx Mode
ANT SW GSMSEL DCSSEL TXPA
EGSM TX 101
DCS TX 011
EGSM RX 100
DCS RX 010
Graph.4-5 Dual Control Signal
forGSM RX Mode
Table.4-2 ANT SW control
Logic
RX_EN
DCSSEL
GSMSEL
TXPA
RX_EN
Low
High
Low
4. TROUBLE SHOOTING
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4-2-5 Checking Saw Filter Circuit
L421
2.7nH
C453
NCNC
C452
10nH
L407
NC
C443
C451
0.5p
G26G3G4
8
1
IN1
3
IN2
7
OUT1
OUT2
5
FAR-G6CS-1G8425-L250
FL406
2G14
L420
1.8nH
3.3nH
L406
FL406.3
FL402.5 FL402.7
FL406.1
4. TROUBLE SHOOTING
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4-2-6 Checking RX IQ
RXIN
RXIP
RXQN
RXQP
Graph 4-7. RX IQ Signal Graph 4-8. RX I Signal (Extended)
4. TROUBLE SHOOTING
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4.3 Tx Trouble
4-3-1 Checking Regulator Circuit
• If you already check this point while checking RX part,
You can skip this test.
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4. TROUBLE SHOOTING
U404. 1 U404. 2 U404. 6
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4. TROUBLE SHOOTING
4-3-2 Checking VCTCXO Circuit
• If you already check this point while checking RX part, You can skip this test.
Graph 4-9. VCTCXO 13MHz Graph 4-10. VCTCXO 2.7V
X401.4 X401.3
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4. TROUBLE SHOOTING
4-3-3 Checking Control Signal
Graph 4-11. RF Control Signal Graph 4-12. TXEN, TXRAMP, TXPA
TP 409(LE) TP404 (RXEN)
TXEN
(TP402)
TXRAMP
(R401)
TXPA
(R404)
TP407(Data)
TP408(Clock)
PLL_LE
PLL_DATA
PLL_CLK
TX_EN
TXRAMP
TXPA
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4. TROUBLE SHOOTING
4-3-4 Checking TX IQ
Graph 4-13. TX IQ Signal
RXIN
RXIP
TXQN
TXQP
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4. TROUBLE SHOOTING
4-3-5 Checking RF TX Level
L419
L402
L401
L427
U401
U416
U402
R405
R404
R403
R401
R406
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