Samsung STH-N375 Service Manual

SERVICE

TDMA MOBILE TELEPHONE

STH-N375

Manual

TDMA MOBILE TELEPHONE CONTENTS

1. Trouble Shooting

2. Electrical Parts List

3. Exploded Views and Parts List

4. Block Diagrams

5. PCB Diagrams

6. Circuit Description & Circuit Diagrams

©Samsung Electronics Co.,Ltd. May. 2002

Printed in Korea. Code No.: GH68-02790A BASIC.

ELECTRONICS

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1-1

1. STH-N375 Trouble Shooting

1. Baseband Section

1-1. Program No Running

N

Need to check

Q107, Q106

N

Need to check

U110, U111, U206

N

Need to replace

Memory(U202)

N

Need to check TCXO OSC302

& neighbor part

Press END

Key

Y

ON_SW=H

VBAT>3.2V

VCTCXO_IN=14.4 MHz

Memory (U202)

control signal

OK?

VCC=3.0V

V_VCTCXO=3.0V

RESET=3.0V

IVCC=2.2V

GBOOT_DI=H

Program Running

VCC, ADD(0:21), DATA(0:15),

FLASH_CS, SRAM_CS, UBE,

MEMOEB, MEMWEB

N

ON_SW=H

Need to check

Key Mat

Need to check

Battery

N

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1-2

STH-N375 Trouble Shooting

1-2. Abnormal LCD Module, Vibrator & Speaker Operation

Y

N

Need to check

CN202-1

Need to check

U312 & neighbor part

N

Need to check

R125, 126

Y

LCD Control

Signal OK?

Y

BACKLIGHT=H

Y

VCC, ADD(2), DATA(0:7),

DISPLAY_CS, RESET

LCD Display Running

Send Command Back Light enable

Y

N

Need to check

R216 & U205

Y

LCD Display Running

Back lingt Running

Send Command Vibrator enable

Need to check

Q109, R130, R162, R163, R164

START

Y

N

Need to check

U101_77,79

Y

LCD Display Running

Back lingt Running

Vibrator Running

Send Command Main Audio Receiver Path ON

Send Command Audio tone generator ON

1

VIBRATOR=H

Vibrator Run

OK?

SPK+,SPK- Signal

OK?

LED Back light

OK?

Y

N

Replace U101

Good

Speaker Output

OK?

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1-3

STH-N375 Trouble Shooting

1-3. Abnormal Buzzer operation

N

Need to check

Q207, D201, U101

START

Y

Send Command Ringer Path ON

Send Command tone generator ON

N

Replace AU201

Y

Buzzer Sound Output

OK?

RINGER(U101_1)

Signal OK?

Buzzer Operation

Good

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1-4

STH-N375 Trouble Shooting

1-4. Abnormal external Ear_Mic Jack operation

START

Y

Hock Up Ear_Mic Phone in the Jack(CN101)

Send Command MIC_BIAS_EN enable

Send Command AMP_EN enable

N

Need to check U106

neighbor parts

Y

HS_SENSE=H

N

Need to check U106

neighbor parts

Y

SEND_END=H

Press Button on the Ear-Jack

Ear_Mic phone

Operation Good

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1-5

STH-N375 Trouble Shooting

2. RF Section

2-1. Call processing and Online Test

N

DONE

START

Y

Normal SVC?

Check RX path

N

Y

Set up Call

OK?

Check TX path

N

Y

Measure

SINAD/BER

Good?

Check RX path

N

Y

Check TX path

Measure

Tx Power

Good?

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1-6

STH-N375 Trouble Shooting

2-2. Receiver Section (Offline test)

1

Y

N

Need to check

U105, Q102

Y

N

Need to check

U306, C349

F303_2=-52dBm

N

Need to check

F302 & neighbor parts

Y

RF_BAND=L, RX_BAT=H

PLL_ON=H, PON_LC=H

VCTCXO_PC=H, IF_ON=H

PON_VRF3=H

set up 8920B basestation for RX test

Set Base station RX Lev=-50 dBm

Send Command Cell band selection

Send Command RX path ON

Send Command channel selecton

START

N

Y

V_LNA_CELL=H

U105_1=H Q102_3=H

Need to check

U300 & neighbor parts

2

U301_45=-39.5dBm

N

Need to check

C324, F303

F303_3, U300_8

=-55dBm

F302_2=-36.0dBm

Y

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1-7

STH-N375 Trouble Shooting

2

N

AMPSTDMA

N

Replace U301

Replace

F301

Need to check

OSC301, neighbor parts

& U301_1,2,3

Need to check

U105 & neighbor parts

N

Y

RF local check

U301_48 Lev=-6dBm

Freq=adjusted freq?

1

U301_41 Lev=-24.5dBm

Freq=130.05MHz

U301_34 Lev=-28.0dBm

Freq=130.05MHz

Need to check

U301, L301, C304, C306, R301

Y

Replace F300 or

Need to check R302, R303, C303

U301_25 Lev=-18.0dBm

Freq=450kHz

MODE

U301_40, 42=3.0V

43

N

U301_37 Lev=-13.0dBm

Freq=450kHz

N

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1-8

STH-N375 Trouble Shooting

N

Replace U301

Case TDMA mode:

setup basestation for RX test

Amplitude:-50dBm

3

U301_9, 10, 11, 12

measure I/Q

Quarature wave

N

Need to check U301 &

Quad LC Tank circuit

(L303, C315, C316,

C317, R307)

PON_LD=H

Case AMPS mode:

setup basestation for RX test

Audio Freq gen : 1004Hz

FM deviation : 2.9kHz

4

Y Y

Y

U301_16 DEMOD (sinusoidal wave)

Vp-p=240mV

Freq=1004Hz

N

Need to check U301 &

R326, R320, C352, C127

U101_52 DEMOD (sinusoidal wave)

MAX Vp-p=1.4V

Freq=1004Hz

N

Replace U203

Y

U101_40 BBCLK=

6.2208MHz or 4.096NHz or

5.12MHz

N

Replace U203

Y

U101_32RX_CLK=

BBCLK/2 or

BBCLK/8

N

Replace U203

Y

U101_31 RX_SYNC=

BBCLK/32 or

BBCLK/128

N

Replace U203

Y

U101_31 RX_DATA=

serial data

DONE