LG KE800 Service Manual page 71

4. Trouble Shooting
4.19.8 Checking TX I/Q Signals
PMB6272
18
R502 820
X2V8 VDDVCO2V8
17
MIX2V8 EN
16
VDDXO2V8
15
FSYS1
14
GND1
13
2V7_VCXO
X501
3 1
OUT VCONT
4 2
VCC GND
C529
26MHz
0.1u
2V85_RF 1V5_CORE
R510
10
C538 C539
0.1u 47n
Figure 17. TX I/Q Circuit
Checking Points
IX I
Q
QX
U501
Figure 18. TX I/Q
RF_EN
26MHZ_MCLK
C521 820p
C528
NA
R508
AFC
620
C533
22p
RF_CLK
RF_DA
C536 C537
NA NA
C552
NA
BT_CLK
QX
Q
IX
I
- 72 -
Checking Flow
Check TX I/Q Signals
No
Signals are
Normal ?
Yes
TX Part is OK.
Check Base Band Circuit
or
Re-Download S/W and Cal.
I
TX
Q
I
Q
Figure 19. TX I/Q Waveform
Replace
Transceiver
PMB6272(U501)