LG W5200 Service Manual Troubleshooting

- 51 -

4. TROUBLE SHOOTING

4.1 Power Supply Failure

Figure 4-1.

4. TROUBLE SHOOTING

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4.2 RX Sensitivity Trouble (EGSM)

Figure 4-2. RX Sensitivity Trouble (EGSM).

4.3 RX Sensitivity Trouble (DCS)

Figure 4-3. RX Sensitivity Trouble (DCS).

U405 pin 10 RF signal

U405 pin 10 RF signalU405 pin 10 RF signal

U405 pin 10 RF signal

is over -65dBm

is over -65dBmis over -65dBm

is over -65dB

Check U405 and

Check U405 andCheck U405 and

Check U405 and peripheral circuit

peripheral circuitperipheral circuit

peripheral circuit

YES

YESYES

YES

YESYES

YES

NONO

U405 : ANT. Switch

U405 : ANT. Switch U405 : ANT. Switch

U405 : ANT. Switch U408 : RF SAW Filter

U408 : RF SAW Filter U408 : RF SAW Filter

U408 : RF SAW Filter U411 : CX74017

U411 : CX74017 U411 : CX74017

U411 : CX74017

(High Frequenc y Probe)

(High Frequenc y Probe)(High Frequenc y Probe)

(High Frequenc y Probe)

U408 pin 3 RF signal

U408 pin 3 RF signalU408 pin 3 RF signal

U408 pin 3 RF signal

is over -68dBm

is over -68dBm is over -68dBm

is over -68dBm

Check U408

Check U408Check U408

Check U408 and

and and

and

peripheral circuit

peripheral circuitperipheral circuit

peripheral circuit

Rework on Calibration

Rework on CalibrationRework on Calibration

Rework on Calibration

YES

YESYES

YES

NONO

@947.4MHz

@947.4MHz@947.4MHz

@947.4MHz

@947.4MHz@947.4MHz

@947.4MHz

START

(62CH, Sector Power - 60dBm)

U401 pin 1 RF signal

U401 pin 1 RF signalU401 pin 1 RF signal

U401 pin 1 RF signal

is over -68dBm

is over -68dBmis over -68dBm

is over -68dBm

Check U401 and

Check U401 andCheck U401 and

Check U401 and

peripheral Circuit

peripheral Circuitperipheral Circuit

peripheral Circuit

YES

YESYES

YES

YESYES

YES

NONO

ANT. Switch

ANT. Switch ANT. Switch

ANT. Switch

U407 : RF SAW Filter

U407 : RF SAW Filter U407 : RF SAW Filter

U407 : RF SAW Filter U411 : CX74017

U411 : CX74017 U411 : CX74017

U411 : CX74017

(High Frequenc y Probe)

(High Frequenc y Probe)(High Frequenc y Probe)

(High Frequenc y Probe)

U407 pin 3 RF signal

U407 pin 3 RF signalU407 pin 3 RF signal

U407 pin 3 RF signal

is over -71dBm

is over -71dBmis over -71dBm

is over -71dBm

Check U407 and

Check U407 andCheck U407 and

Check U407 and

peripheral Circuit

peripheral Circuitperipheral Circuit

peripheral Circuit

Rework on Calibration

Rework on CalibrationRework on Calibration

Rework on Calibration

YES

YESYES

YES

NONO

@1842.6MHz

@1842.6MHz@1842.6MHz

@1842.6MHz

@1842.6MHz@1842.6MHz

@1842.6MHz

START

(699CH, Sector Power - 60dBm)

4. TROUBLE SHOOTING

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4.4 TX Power Trouble

Figure 4-4. TX Power Trouble.

Setup Te st with RFCAL

Setup Te st with RFCALSetup Test with RFCAL

Setup Te st with RFCAL

GSM:62CH, DA C value 600 DCS:700CH, DAC value 700 Power Level: GSM 5, DCS 0

Test DC Voltage :4 V

U105: AD6522 (D ig ital) U103: AD6521 (An alog) U409: PAM (PF08107B) U411: RF Main Chip (C X74017) U405: ANT S/W (LM G002S- 5008C) U412: APC IC (AD8315) N401: Directional coupler (LD C15D190A0007A)

Is the Modul ated Tx s ignal of U409 (GSM:pin1)

about -2 dBm,(DCS pin8) about -2d Bm?

(GSM 902. 4MHz, DCS 1747.8MHz)

Is the amplif ied Tx s ig nal o f U409(GSM:p in4)

about 9.3dBm,(DCS:pin5) about 8.5dBm?

Is the input powe r of U405(GSM:pin5)

about 10dBm,( DCS:pin1) about 9d Bm?

Check or change resistors between U411 and U409

Check the Tx IQ Signal level of U411

(pin20, 21, 22, 23)

(DC1.17V, 0.97V p-p swing s ignal)

Check or c hange U411 o r U103 and peripheral circuit

Is the Modul ated Tx signal of U411 (GSM:pin64)

about 7.5dBm,(DCS:pin1) about 6.5dBm?

(GSM 902.4MHz, DCS 1747.8MHz)

Check or change U411 and peripheral circuit

Is th e o u tput voltage level of U41 2(Vapc:pin7)

about 1.18V?

Change U409

Is the TXEN signal level of U412(ENBL:pin2)

High(over 2.8V)?

Change U105

Change U412

Check ca libration da ta

and c hange U405

YES

Is the TXRAMP signal vo ltage of

U412(VSET:pin3) over 1.2V?

Change U103

YES

Check or change N401 and

peripheral circuit .

EGSM

DCS

GSMSEL DCSSELANT S/W TXPA

Truth Table

1 0 1 0 1 1

EGSM

DCS

BANDSEL1 BANDSEL2TRANSCEIVER

Truth Table

0 EGSM

DCS

GSMSELPAM

Truth Table

1 01

0 0

4. TROUBLE SHOOTING

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4.5 RX Trouble

START

PIF Power On

RF2.85V

O.K?

RFMain Chip O.K?

Ref. Clock 13MHz O.K?

YesYes

U414Check!! Pin 2

3.2 V

Pin 1. 2.85V

Y401Check!!

Pin 4. 2.7V

P in 3. 13MHz

U411Check!!

NoNo

Yes

Block 2

Block 3

Block 4

Block 6

NoNo

Antenna S/W

RX O.K?

Goto Block 2 Test.

Goto Block 3 Test

Goto Block 4 Test

U405Check!!

YesYes

RX Path Working !

RFFilterO.K?

U407, U408Check!!

Block 4

NoNo

Goto Block 5 Test

YesYes

Goto Block 6 Test

Setting : After Initialize Agilent 8960, Test in EGSM or DCS Mode

4. TROUBLE SHOOTING

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Block 2 Test ) U414 (RF 2.85V) Check!!

Voltage> 3.2V ?

NoYes

RF 2.85V O.K?

Yes

Check Placement of U414 VBAT Line Check Short?(Using Multi Meter)

If it has not problem

Check Placement of U414 Check RF2.85V Line. Short?(Using Multi Meter)

Replace U414

2-B Test!!

U414Work ing

Goto Block3 !!

Pin 6.High ?

Yes

Check U105

If it has not problem

U414.1

U414.6

U414.2

2-A) Check Pin 2. Using Oscilloscope

2-B) Check Pin 6. Using Oscilloscope

2-C) Check Pin 1. Using Oscilloscope

4. TROUBLE SHOOTING

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Block 3 Test) Y401 (13MHz Oscillator) Check!!

Y401.3

Y401.4

Voltage 2.7V ?

NoYes

13MHz Output ?

Yes

Replace U101

Replace Y401

3-C) Test!!

Pin 1.High ? AFC LineShort?

13MHz Line Short?

Yes

Check Short

3-C) Test!!

Yes

Y401Working

Goto Block 4

U413Working?

U101 Pin 25. 2.7 V?

Check Short

3-B) Test!!

Yes

Replace U103

Replace U413

3-C) Test!!

3-A) Check Placement of Y401

3-B) Check Pin 4. Using Oscilloscope.

3-C) Check Pin 3. Using Oscilloscope.

4. TROUBLE SHOOTING

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Block 4 Test) U411 (RF Main IC) Check!!

GSM : CH40, -60dbm

DCS : CH700, -60dbm

U411.13

U411.11

4. TROUBLE SHOOTING

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Block 4 Test) U411 (RF Main IC) Check!!

4-A) Check Placement of U411 4-B) Check U411 Pin 11, Using Spectrum Analyzer

4-C) Check U411 Pin 13, Using Spectrum Analyzer

-68dBm

-71dBm (2)

(1)

GSM SAW Filter

Output ~ -68dbm ?

5-A Test!!

Yes

U411 Working

Goto Block 5

DCS SAW Filter

Output ~ -71dbm ?

5-A Test!!

Yes

4. TROUBLE SHOOTING

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Block 5 Test) U408(GSM Filter), U407(DCS Filter) Check!!

GSM : CH40, -60dbm

DCS : CH700, -60dbm

5-A) Check Placement of U408, U407

5-B) Check U408 Pin 1, 3 Using Spectrum Analyzer

5-C) Check U407 Pin 1,3 Using Spectrum Analyzer.

NoYes

Check Soldering

Replace U408

5-B) Test!!

RF Output

Pin 1 ~ -65dbm ?

Pin 3 ~ -68dbm ??

GSM BAND PASS FILTER

RF Output

Pin 1 ~ -68dbm ?

Pin 3 ~ -71dbm ?

Yes

Replace U407

5-C) Test!!

Goto Block 6 !

DCS BAND PASS FILTER

U407.1

U407.3

U408.1

U408.3

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