4.3 TX Trouble. LG KG291, KG290

4. TROUBLE SHOOTING

4.3 TX Trouble

Checking Flow

START

HP8960 : Test mode

62 CH, 7 level setting (TCH)

62CH, -60dBm setting (BCCH)

Spectrum analyzer setting

Oscilloscope setting

(1)Check

Crystal Circuit

(2)Check

Mobile SW

& FEM

(3)Check

PAM control signal

(4)Check

TX I/Q Signal

Redownload SW or

Do calibration again

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Only for training and service purposes

4. TROUBLE SHOOTING

(1) Checking Crystal Circuit

TEST POINT

C547

R520

CHECKING FLOW

26 MHzO.K?

Yes Crystal Circuit is OK

Change X500

X500

CIRCUIT

C543

1000p

2V75_VVCXO

U502

2

VCC

5

GND

3

4

R520

1M

C547

2.2u

26M_DBB

WAVEFORM

Graph 4.3.1(a)

Copyright © 2007 LG Electronics. Inc. All right reserved.

Only for training and service purposes

- 63 -

Graph 4.3.1(b)

LGE Internal Use Only

4. TROUBLE SHOOTING

(2) Checking Mobile SW & FEM

TEST POINT

RF 600.ANT

RF 600.RF

RF600

Vdd (C534)

Vdd (C535)

Vctrl 1

Vctrl 2

Vctrl 3

FL500

CIRCUIT

TP501 TP500 TP502

Waveform

R590 NA

RF-600

SW500

G1 G2

NA R505

C517

22p

Vctrl 1

Vctrl 2

Vctrl 3

2V75_VVCXO

FL500

YGHF-S006T

10

9

7

5

4

2

GND6

GND5

GND4

GND3

GND2

GND1

20

21

22

3

VCTRL3

VCTRL2

VCTRL1

VDD

C534

39p

C535

0.1u

11

TX2G

TX1G

8

6

PCS_RX+

PCS_RX-

DCS_RX+

DCS_RX-

EGSM_RX+

EGSM_RX-

NC2

NC1

13

12

15

14

17

16

19

18

C544

39p

C545

39p

C546

39p

Graph 4.3.2(a) GSM Tx mode

Vctrl 1

Vctrl 2

Vctrl 3

ANT_SW1

ANT_SW2

ANT_SW3

Graph 4.3.2(b) DCS,PCS Tx mode

LGE Internal Use Only - 64 Copyright © 2007 LG Electronics. Inc. All right reserved.

Only for training and service purposes

4. TROUBLE SHOOTING

Checking Flow

For the test,

TX Stand alone Mode is needed. Refer to chapter 10 (PL=7 for EGSM, PL=2 for

DCS&PCS)

Check C544,C545,C546

Check whether Ant SW

Set as TX mode

Refer to Graph 4.3.2

Refer to Table 4.3.2

Check RF Level of

FL500 Pin 6(for EGSM) &

Pin 8(for DCS&PCS)

Check Vctrl 1,2,3 & Vdd

Yes

Check RF600.ANT, RF with RF

Cable connected.

Pin6 : ~29.5dBm

Pin8 : ~26.5dBm

Yes

Open

Yes

Check RF600.ANT,RF with RF Cable disconnected

Short

Yes

END

No

No

No

No

Changing board

Go to 4.3.4 Checking PAM control signal

Changing RF600

Changing RF600

TX Mode

Vctrl 1

Vctrl 2

Vctrl 3

EGSM

On

Off

Off

Table 4.3.2

DCS/PCS

On

On

Off

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Only for training and service purposes

- 65 LGE Internal Use Only

4. TROUBLE SHOOTING

(3) Checking PAM Control Signal

TEST POINT

C506

(PAM_EN)

U500

CIRCUIT

VBAT u

C502

18p

C503

33p

C504

22u

C508

0.01u

C509

0.01u

15

DCS_PCS_OUT

11

19

EGSM_OUT

U500

SKY77318

RSVD_GND

DCS_PCS_IN

3

EGSM_IN

4

ENABLE

18

21

P_GND BS

1

5dB

4dB

R508

220

R507

24

R511

R510

180

30

R509

220

C511 33p

R512

180

C513 10p

C514

39p

QP

QN

C505

68p

C506

27p

C507

27p

R500 100ohm

R501 100ohm

R503 68

PA_BAND

PA_EN

TX_RAMP

C543

1000p

U502

2

VCC

5

GND

3

MC74VHC1G04DFT2G

C5

0.

C505

(TX_RAMP)

Figure 4.3.3

Waveform

Checking Flow

Check TX_RAMP and PAM_EN

Check if there is

Refer to Graph 4.3.3

Graph 4.3.3

Go to Next Step

LGE Internal Use Only

Re-dow nload

S/W

- 66 Copyright © 2007 LG Electronics. Inc. All right reserved.

Only for training and service purposes

4. TROUBLE SHOOTING

(4) Checking TX I/Q

TEST POINT

C514

C541

U501

Waveform

Graph 4.3.4

Figure 4.3.4

CIRCUIT

C514

39p

C519

0.1u

0.15MM

29

30

31

32

25

26

27

28

RX1900B

RX1900

RX1800B

RX1800

RX900B

RX900

RX850B

RX850

33

GND

U501

AD6548

VLDO2

VLDO1

VBAT

VDD

VCC_TXVCO

TXOP_HI

TXOP_LO

VLDO3

16

15

14

13

12

11

10

9

QP

QN

C541

39p

IP

IN

Checking Flow

Check if there is

Any Major Difference

Refer to Graph4.3.4

Similar?

Yes

Re-download the Software

And calibrate

No

Replace U501

Copyright © 2007 LG Electronics. Inc. All right reserved.

Only for training and service purposes

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