LG ID2750 Service Manual
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LG ID2750 Service Manual

LG ID2750 Service Manual

Cdma mobile subscriber unit
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Features of Mobile Subscriber Radio Handset
(LG-ID2750 Type)
1. Wave Type
• G7W
2. Frequency Scope
• Transmit Frequency : 824.820 ~ 848.190MHz
• Receive Frequency
3. Rated Output Power
• 0.282W(24.5dBm)
4. Output Conversion Method :
5. Voltage and Current Value of Termination Part Amplifier(Catalogue included)
Mode
CDMA
6. Functions of Major Semi-Conductors
Classification
MSM6000-208Pin-FBGA
FLASH MEMORY
(K8D3216UTC-TI07)
STATIC RAM
(K1S161611A-FI70)
RFT6122 & RFR6122
7. Frequency Stability
• ±0.5PPM
LGE
LG Electronics Inc.
: 869.820 ~ 893.190MHz
This is possible by correcting the key boaID channel.
Type Name
Voltage
FC7113
3.7V
Operation control and digital signal processing of the mobile station
Flash Memory (32Mbit) ▶ Storing of the mobile station operation
program
SRAM (16Mbit) ▶ Temporary storing of the data created while
busy
Converting baseband signal into Tx RF signal and Rx RF signal
into baseband signal
Current
600mA
Function
Power
0.32W

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Summary of Contents for LG ID2750

  • Page 1 Features of Mobile Subscriber Radio Handset (LG-ID2750 Type) 1. Wave Type • G7W 2. Frequency Scope • Transmit Frequency : 824.820 ~ 848.190MHz • Receive Frequency : 869.820 ~ 893.190MHz 3. Rated Output Power • 0.282W(24.5dBm) 4. Output Conversion Method : This is possible by correcting the key boaID channel.
  • Page 2 CDMA MOBILE SUBSCRIBER UNIT LG-ID2750 SERVICE MANUAL SINGLE BAND CDMA MOBILE PHONE...

  • Page 3: Table Of Contents

    CHAPTER 2. NAM Input Method(Inputting of telephone numbers included) 1. Telephone Number and NAM Programming Method .............. 14 CHAPTER 3. Circuit Description 1. RF Transmit/Receive Part ....................... 17 2. Digital/Voice Processing Part ....................22 CHAPTER 4. Trouble Shooting LG Electronics Inc. 1/26...
  • Page 4 LG-ID2750 General Introduction The LG-ID2750 cellular phone functions as digital cellular phone worked in CDMA (Code Division Multiple Access) mode. CDMA mode applies the DSSS (Direct Sequence Spread Spectrum) technique that has been used in military. This technique enables to share one frequency channel with many users in the same specific area.

  • Page 5: Chapter 1. System Introduction

    Another method available is to make two persons to sing in different languages at the same time, space, and frequency when wishing to let the audience hear the singing without being confused. This is the characteristics of CDMA. LG Electronics Inc.
  • Page 6 At this time, the spectrums of other signals that have different codes are not recovered into its original state and instead, processed as noise and appears as the self-interference of the system. LG Electronics Inc. 4/26...

  • Page 7: Features And Advantages Of Cdma Mobile Phone

    The backwaID open loop power control is carried out in a corresponding mobile station; the mobile station measures power received from the cell site and then, reversely increases/decreases transmit power in oIDer to compensate channel changes caused by the forwaID link path loss and terrain LG Electronics Inc. 5/26...
  • Page 8 During the soft hand, the cell site already in the busy state and the cell site to be engaged in the call later participate in the call conversion. The call conversion is carried out through the original call LG Electronics Inc. 6/26...
  • Page 9 In addition, in the CDMA system, services and service charges are classified further into different classes so that more transmit power can be allocated to high class service users for easier call set-up; they can also be given higher priority of using hand-off function than the general users. LG Electronics Inc. 7/26...

  • Page 10: Structure And Functions Of Cdma Mobile Phone

    (AGC Amp). Then, they are converted into RF band by the frequency synthesizer synchronizing these signals to proper output frequencies. Transmit signals obtained pass through the duplexer filter and then, are sent out to the cell site via the antenna. LG Electronics Inc. 8/26...

  • Page 11: Specification

    StandaID (1000mAh) Stand-By Time 160 Hrs (SCI=1) Talk Time 180 Min (About +92dBm, Half rate) 4.2 Receive Specification 4.2.1 Frequency Range : 869.820 MHz ~ 893.190 MHz 4.2.2 Local Oscillating Frequency Range : 1738.08MHz ~ 1787.94MHz LG Electronics Inc. 9/26...
  • Page 12 4.3.5 CDMA TX Frequency Deviation : 4.3.6 CDMA TX Conducted Spurious Emissions • 900kHz : - 42 dBc/30kHz below • 1.98MHz : - 54 dBc/30kHz below 4.3.7 CDMA Minimum TX Power Control : - 50dBm below LG Electronics Inc. 10/26...
  • Page 13 874.560 MHz 887.04 MHz 875.790 MHz 888.270 MHz 877.020 MHz 889.500 MHz 878.250 MHz 890.910 MHz 879.480 MHz 892.140 MHz 880.890 MHz 893.370 MHz 4.6 Charge time 4.6.1 StandaID Battery : Typical 120 ~ 180 Min. LG Electronics Inc. 11/26...

  • Page 14: Installation

    IB bracket with the four self-tapping screws provided. Clip the IB into the IB bracket. 5.3.3 Microphone Installation Install the microphone either by cliiping I onto the sunvisor (driver’s side) or by attaching it to door post (driver’s side), using a velcno adhesive tape (not included). LG Electronics Inc. 12/26...
  • Page 15 Connect the kit’s power cable connector to the interface box power receptacle. 5.3.4.2 Antenna Cable Connection Connect the antenna coupler cable connector from the cradle to the external antenna connector. ( Antenna is not included.) LG Electronics Inc. 13/26...

  • Page 16: Chapter 2. Nam Input Method(Inputting Of Telephone Numbers Included)

    • You can’t edit PHONE MODEL , then press [OK]. DEBUG MENU Service Mode SLOT CYCLE INDEX Test Screen Test Call Vocoder Set Hybrid Pref • You can edit SLOT CYCLE INDEX (, but not recommended ), then press [OK]. LG Electronics Inc. 14/26...
  • Page 17 Standard Program Test Screen IS COMPLETE Test Call Vocoder Set Hybrid Pref • Now, the basic programming is completed. To reset the handset, press [Done]. If you want to program detail informtions for NAM 1, press [Add]. LG Electronics Inc. 15/26...
  • Page 18 NAM 1 Lock out SID/NID NAM 1 CDMA Primary CH A NAM 1 CDMA Secondary CH A NAM 1 CDMA Primary CH B NAM 1 CDMA Secondary CH B NAM 1 ACCOLC 0 ※ Editing this items is not recommended. LG Electronics Inc. 16/26...

  • Page 19: Chapter 3. Circuit Description

    After that, the RF signal is amplified by the Power Amp in oIDer to have enough power for radiation. Finally, the RF signal is sent out to the cell site via the antenna after going through the duplexer LG Electronics Inc. 17/26...
  • Page 20 LG-ID2750 [Figure 3-1] Block Diagram Of ID2750 1.2 Description of Receive Part Circuit 1.2.1 Duplexer (DP100) The duplexer consists of the receive part bandpass filter (BPF) and the transmit part bandpass filter (BPF) which have the function of separating transmit/receive signals in the full duplex system using the transmit/receive common antenna.
  • Page 21 LG-ID2750 The specifications of ID2750 LNA are described below Parameter Gain Mode 0(G0) Gain Mode 1(G1) Gain Mode 2(G2) Gain Mode 3(G3) Unit Gain Noise Figure Input IP3 1.2.3 Rx RF SAW FILTER (F101) The main function of Rx RF SAW filter is to attenuate mobile phone spurious frequency, attenuate noise amplified by the LNA and suppress second harmonic originating in the LNA.
  • Page 22 The module of power amplifier is made up of an output end interface circuit including this module. The maximum power that can be inputted through the input terminal is +7dBm and conversion gain is about 28.5dB. RF transmit signals that have been amplified through the power amplifier are sent to the duplexer. LG Electronics Inc. 20/26...
  • Page 23 VCO frequency. This assures that the VCO frequency is different than the RF frequency, an important consideration for Zero-IF processing. The VCO frequency used are 1738.08~1787.94MHz for cellular and It is produced in single voltage controlled oscillator of U106. LG Electronics Inc. 21/26...

  • Page 24: Digital/Voice Processing Part

    2.2.5 Power Supply Part (U400, PM6610-2) The power supply part (PM6610) is made up of devices for generating various types of power, used for the digital/voice processing part and one DC/DC converter directly connetted to Batterry for LCD display. LG Electronics Inc. 22/26...
  • Page 25 They are voice decoded at the vocoder in oIDer to output digital voice data. The MSM6000 also supports Enhanced Variable Rate Coder (EVRC) operation in addition to the standaID 8k and 13k vocoding rating. 2.3.2.1 Audio Processing Part LG Electronics Inc. 23/26...
  • Page 26 MSM6000. The Tx part regulator (+2.6V_TX) is operated by SBI(Seiral Bus Interface) control signal from MSM6000. The block diagram of power management IC is shown in [Figure 3-2]. [Figure 3-2] Block Diagram Of Power Management IC LG Electronics Inc. 24/26...
  • Page 27 ARM microprocessor include a 3 stage pipelined RISC architecture, both 32-bit ARM and 16-bit THUMB instruction sets, a 32-bit address bus, and a 32-bit internal data bus. It has a high performance and low power consumption. FLASH ROM and SRAM LG Electronics Inc. 25/26...
  • Page 28 MSM6000. It is also supplied stable 2.85V_MSMP by inner regulator in U400 for fine view angle and and LCD reflects to improve the display efficiency. 2 white LEDs are used to display LCD backlight LG Electronics Inc. 26/26...
  • Page 29 CHAPTER 4. Trouble Shooting CHAPTER 4. Trouble Shooting 4.1 Rx Part Trouble 4.1.1 When Rx Power isn’t enough Test Point Duplexer VCTCXO PMIC RFR6122 VCTCXO Figure 4-1 Checking Flow START Rx TEST SETUP(HHP) - Test Channel : 384 E5515C Setup - CH : 384 - Sector Power : -30 dBm Spectrum Analyzer Setting...
  • Page 30 4.1.2 Checking Regulator Circuit Test Point U400. 7 High U400. 31 (+2.6V_RX) Figure 4-2 Circuit Diagram Checking Flow Check Pin 7 of U400 Changing Board +2.6V_Rx OK? Pin 7. High? Check Pin 31 of U400 PMIC Circuit is OK See Replace U400 next Page to check VCTCXO...
  • Page 31 4.1.3 Checking VCTCXO Circuit Test Point Checking Flow U407. 4 Check U407 Pin 3 ◆ Refer to Graph 4-1(a) U400. 32 VCTCXO Circuit is Ok 19.2MHz OK? See next Page to check Rx VCO CheckU407 Pin 4 ◆ Refer to Graph 4-1(b) +2.8V_TCXO OK? Changing U407 U407.
  • Page 32 4.1.4 Checking Rx VCO Signal Test Point U104.16 (CP_RX) U104.18 (UHF_LO_OUT) Figure 4-4 Checking Flow Rx TEST SETUP(HHP) - Test Channel : 384(DCN),600(PCS) Spectrum Analyzer Setting Oscilloscope Setting Check U104 Pin 18 Rx VCO is Ok Check if there is UHF_LO OK? See next Page Any Major Difference...
  • Page 33 1763.04MHz @ DCN384 DCN Mode Graph 4-2...
  • Page 34 4.1.5 Checking Control Signal U104. 4 (SBCK) Test Point U104. 5 (SBST) U104. 3 (SBDT) Figure 4-5 Checking Flow Check Pin 3, 4, 5 Download the SW Level is High? ◆ Refer to Graph 4-3(a,b) Check SBDT, SBCK SBST Check if there is Similar? Download the SW Any Major Difference...
  • Page 35 4.1.6 Checking Mobile SW & SP3T & Duplexer(DCN,PCS) Test Point U100. 2 DP101. 2 DP101. 7 Figure 4-6 Circuit Diagram...
  • Page 36 Checking Flow Rx TEST SETUP(HHP) - Test Channel : 384(DCN),600(PCS) E5515C Setup - CH : 384(DCN),600(PCS) - Sector Power : -30 dBm Spectrum Analyzer Setting Oscilloscope Setting Check U100 Pin 2 Check if there is Detected Signal? Changing U100 Any Major Difference ◆...
  • Page 37 Waveform DP101 Pin2 Graph 4-4(c) DP101 Pin 7 Graph 4-3(c)
  • Page 38 4.1.7 Checking Rx I/Q data Test Point U104. 28 (Rx_I_P) U104. 27 (Rx_I_M) U104. 26 (Rx_Q_M) U104. 25 (Rx_Q_P) Figure 4-7 Waveform U104. 28 (Rx_I_P) U104. 27 (Rx_I_M) U104. 25 (Rx_Q_P) U104. 26 (Rx_Q_M) Graph 4-5(b) Graph 4-5(a) Checking Flow Check U104 Pin 25, 26, 27, 28 Replace U104 Similar?
  • Page 39 4.2 Tx Trouble Test Point Duplexer VCTCXO Mobile S/W RFT6122 Checking Flow START √ Connect the phone to UART connector √ Press H/W or F7, then click ‘offline-d’ -Click ‘Band select‘ to cdma & Tx on &Power Amp 4. Check RFT6122 Circuit -Set channel to 384 &...
  • Page 40 4.2.1 Check Regulator(PMIC) Circuit U400 Pin 13 (+2.85V_TX_REG) TEST POINT U400 Pin 16 (+2.8V_MSMP) U400 Pin 4 (+4.2V_Vbatt) U400 Pin 29 (+2.6V_Tx) Circuit Diagram Checking Flow U400 U201 +2.6V_TX +2.8V_MSMP U201 Pin E14 Check Pin 4, 13, 16, 29 +2.85V_TX_REG Replace U201 TX ON High? +4.2 Vbatt...
  • Page 41 4.2.2 Check VCTCXO Circuit TEST POINT Checking Flow X100 U407 Pin4 ( +2.8V_TCXO) Pin 3 VCTCXO Circuit is OK 19.2MHz OK? See next page to check SBI control signal Pin4 Replace U407 2.8V OK? U407 Pin3 Check U400 (TCXO) Circuit Diagram Waveform U407 Pin4 +2.8V_TCXO U407 Pin3 TCXO...
  • Page 42 4.2.3 Check SBI Control Signal Test Point U103 Pin 1, 2, 32 (SBST,SBDT,SBCK) Circuit Flow Download the SW Check Pin 1,2,32 Level is appear? Similar Waveform? Download the SW Control Signal is OK See next page to check RFT6122 Circuit Waveform SBDT SBST...
  • Page 43 4.2.4 Check RFT6100 Circuit Test Point U103 Pin23 (CELL_OUT) U103 Pin12 C158,C159 (TX_CP) (TX_I, Q) Circuit Flow Check U201 Check C158,C159 I,Q Level is Appear? Replace U103 Level (near 1V) is Appear? Check U103 Pin12 Output signal Check U103 Pin23 Replace U103 CELL is Appear? Control Signal is OK...
  • Page 44 Circuit Diagram SPECTRUM ANALYZER CONDITION Waveform -RBW : 1MHz,VBW: 1KHz -Span : 60MHz -Frequency : DCN( 836.52MHz) C158,C159 TX_I,Q DATA U103 Pin23 DCN_OUT...
  • Page 45 4.2.5 Check PAM Circuit Test Point U102 Pin2 (RF_IN) U102 Pin 1,8 (Vcc1,2) U102 Pin3 (Vmode 0.7~2.1V) U102 Pin7 U102 Pin4 (RF_OUT) (Vref +2.85V) Circuit Diagram...
  • Page 46 4.2.6 Check Duplexer & Mobile SW TEST POINT DP100 PIN2 DP_out U100 PIN1 Mobile S/W out Circuit Flow Check DP100 Pin2 Replace DP100 Level is Appear? DUP_OUT Level is Appear? Check U100 Pin1 Replace U100 Redownload SW and Recalibration...
  • Page 47 Circuit Flow Check U102 Pin2 Check F100 Input Level is Appear? RF_IN Check U102 Pin4 Vref 2.7~2.85V Check Q100, U400 V_REG Check U102 Pin3 Level is DCN:Vcont (0.7v~2.1v) Check U201 Check U102 Pin1, 8 Level is Replace U101 VCC1,2 3.4V~4.2V OK? Check U102 Pin7 Output Level Replace U102...
  • Page 48 Circuit Diagram...
  • Page 49 4.3 Logic Part Trouble Figure 4.3.1 PMIC(PM6610) FUNCTIONAL BLOCK DIAGRAM...
  • Page 50 4.3.1 Power On Trouble Circuit Diagram Figure 4.3.2 Power Management circuit diagram Test Points 16 (+2.8V_MSMP) 14 (+2.4V_MSMC) 11 (+2.6V_MSMA) 29 (+2.6V_TX) 8 (PWR_ON_SW) U400 7 (PS_HOLD) PMIC U201(MSM) 32(+2.8V_TCXO) 31 (+2.6V_RX) Figure 4.3.3 PM6610 POWER MANAGEMENT SECTION...
  • Page 51 Checking Flow START Check Battery Voltage Charge of Change Battery and try again > 3.2V ? Push power-on key and check Check the contact of power-key the level change of or dome switch U400 PWR_ON_SW high? Check the voltage of the following port at U400 +2.4V_MSMC Replace U400...
  • Page 52 4.3.2 Charging Trouble Test Points Block Diagram Q401 Q401 R461 U400 Figure 4.3.4 CHARGER CIRCUIT PART Circuit Diagram Figure 4.3.5 PM6610 CHARGING CONTROL BLOCK...
  • Page 53 Checking Flow SETTING : Connect the battery and the charging adaptor (TA) to the phone START Charging Connector Re-soldering CON300 CON300 Well-soldered? Voltage at The charging adaptor (TA) is out of order. Pin1(V_CHAR) Change the charging adaptor. of CON300 = 5V? Q401,R461 Re-Soldering Q401,R461 well-soldered?
  • Page 54 Pin6 (AUDIO_GAI N_SEL) 4.3.3 Audio AMP Trouble Test Points L404 R428 U409 U408 R422 Pin6 U401 CON403 (+VBATT) L403 R423 Pin4 (SPK_-IN) Figure 4.3.6 RECEIVER PART Circuit Diagram Figure 4.3.7 RECEIVER PART Block Diagram Figure 4.3.8 RECEIVER CODEC BLOCK...
  • Page 55 Checking Flow SETTING : “Ringers” at Sounds menu START Voltage at Pin6 of Change main board. U401 is over Internal pattern is opened 3.4~4.2V? Check the contact of speaker or Does Speaker work Properly? Replace the speaker Check the Re-soldering R423 soldering R423 The R423(SPK_EN) is High? Replace the MSM or Board...
  • Page 56 4.3.6 MIC Trouble Mic filter Test points C440 U403 C439 R434 Figure 4.3.9 MIC & BIAS PART Figure 4.3.10 MIC FILTER PART Circuit Diagram Figure 4 .3.11 MIC & MIC FILTER...
  • Page 57 Checking Flow SETTING : After initialize 5515C, Test US Cellular START Voltage at R434 = 1.2V? Check the soldering Re-solder R434 (MIC BIAS Voltage Check) Of R434 Replace MSM Check the signal level Replace the microphone At each side of MIC. Is It a few tens mVAC? Check the soldering of Re-solder C439, C440...
  • Page 58 4.3.7 Vibrator Troble Checking Flow R416 R417 Q406 LED414 Q403 R436 Figure 4.3.12 Vibrator PART Circuit Diagram Figure 4.3.13 VIBRATION CONTROL BLOCK...
  • Page 59 Checking Flow SETTING : “Vibrator on” at Sounds of test menu START Check the state of Re-contact vibrator Contact of Vibrator Does Vibrator work Properly? Replace Vibrator Check the soldering of Is the voltage across LED414 Re-soldering Q406, R417, LED414 Q406, R417, LED400 over 2.5V? Replace Q406, R417, LED414...
  • Page 60 4.3.8 Key Backlight LED Trouble Test Points R415 Q400 Figure 4.3.14 KEYPAD BACK LIGHT PART Figure 4.3.15 KEYPAD Back Light Circuit...
  • Page 61 Checking Flow START Is the voltage level VBATT Charge or Change Battery and try again 3.2-4.2V? Are all LEDs LED404~417 Check the soldering of each R or working? replace LEDs not working Check the condition of Q400, R415. Q400, R410 is working? If problem, Change Q400, R415.
  • Page 62 4.3.9 Earphone Trouble Test Points C430 R206 U203 U404 C212 R207 CON401 Figure 4.3.16 EAR MIC JACK PART Circuit Diagram Figure 4.3.17 EAR MIC JACK PART...
  • Page 63 Checking Flow SETTING : After initialize 5515C, Test US Cellular START Insert the earphone to the handset. Earphone detect problem Does the audio Profile of the phone change to the earphone mode? Audio path problem Set the audio part of the test equipment to echo mode Set the audio part of the test equipment to...
  • Page 64 Earphone detect problem Earphone detect problem Level of pin 5 of CON401 Level of R206, R207 about 1.6V? about 2.4V? Re-soldering R206, R207 Check soldering Re-solder U404 U404 Check working Replace U404 U404 Earphone sending path problem Earphone sending path problem Re-download Level pin4 of CON401 Re-solder...
  • Page 65 4.3.10 LCD Trouble Test Points R400:403 Q405 C315 U202 LED400:403 Q300 CON303 L300 Figure 4.3.18 LCD CONNECTOR PART VR300,VR301 C326 Circuit Diagram Figure 4.3.19 LCD CONNECTOR...
  • Page 66 Checking Flow : LCD START Check L300, C315 Voltage Re-Soldering L300,C315 (MSMP)= 2.8V ? Check the Re-Soldering CON303 CON303 Soldering Does LCD work properly? Check voltages at each Change the LCD Module point of Capacitor. Check the Control signal Does VR300,VR301, R326 Re-soldering or Replace D[0:7], LCD_RESET/, Work Properly?
  • Page 67 Checking Flow : Back Light START Check the LED400:403 Re-soldering or Replace R400:403 LED400:403, R400:403 Re-Soldering or Does Q405 work Properly? Replace Q405 Check the signal level at Replace MSM LCD_BACK_EN=high? LCD backlight will work properly...
  • Page 68 4.3.11 When UIM isn’t operating Test Point Q407 No.1 CON402 No.1 Circuit Diagram...
  • Page 69 Checking Flow...

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