LG-200 Series Repair Trouble Shooting Level I ~ III VER.1.0

I. Introduction Purpose : –In planning to be the reference for repairing LG-200 Dual band mobile phones. –For the regular failure repairing reference. –Contents with full level repairs (Level 1~3) Applicability : –This trouble shooting is only applicable to professional engineer for repairing mobile phone.

II.Contents II-1. Power supply II-2. Voice II-3. Display II-4. Function II-5. Transmission & Receiving

II-1. Power Supply Failure

Failure: –Cant charger battery –Charge connector damage. Solution: -Replace connector J5. -Control the temperature and air flow carfully. J5

GSM Cell Phone Failure: –Long period of charging Battery. Solution: - Use Mutil-matter to check the voltage of pin4 of Q1 while charging, this point should be Low voltage. The failure could be coused by Q33, Q4 or Q1 if the voltage is abnormal. Q1 Q33 Q4

Failure : –Power Supply Circuit Failure Solution : –Test the sets current by using battery simulator,observe the value of current used. –Case 1. If the current is higher 300mA, please check C333. Replace C333 if it has any resistance. C333

GSM Cell Phone Case 2 : –Check the output of regulator U24 and U25. The output voltage should be 2.85V. –Replace regulator which without 2.85V output. U25 U24

Case 3: –In case the current is between 35 and 45 mA, the cause could be FLASH ROM (U12) defect. Please reinstall software. –If the software cant be reinstalled, please replace U12 U12

Case 4: –Check the voltage output of Pin1 of U41, the output voltage should be between 2.8V and 3.5 V. – Please replace U41 if there is no output or value abnormal. U41

GSM Cell Phone Case 5: –Check the voltage output of Pin3 of U39, the output voltage should be above 3.5 V. – Please replace U39 if there is no output or voltage abnormal. U39

Case 6: –If the value of current looks like short circuit, please replace U9 or U32. U32 U9

GSM Cell Phone Case 7: - Check the system clock(13 MHz) on the pin1 of U15. -If there is no 13MHz system clock, the failure should be caused by U35 or U15. U15(CPP)

Failure –Phone set and battery over heat. Short suspend time. Solution –Test the sets current by using battery simulator,observe the value of current used.If the current is up to 300mA take out U9 or U32 and repeat above motions again, replace U9 or U32 if new value is 0. U32 U9

II-2. Voice function failure

GSM Cell Phone Case 1. Replace a new Microphone and try again. Failure - Microphone voice failure. Solution Microphone

–Case 2. –Test the resistance of C18 capacitor by using multi-meter. Replace C18 if there is any resistance has been detected. C18

GSM Cell Phone –Case 3. –The fault could be caused by DSP U1 coldering or defedt. U1 (DSP)

Failure –Hand free function failure Solution –J5 Cold soldering. Please re-solder again. –J5 broken, please replace connector J5. J5

GSM Cell Phone Replace a new Receiver and try again. Failure - No receiving sound( Earpiece). Solution Receiver

II-3. Display function failure

Failure: –LCD broken Solution: - Replace whole LCD modular. - Soldering the LCD modular with care. *LCM Broken should be the customer damaged. LCM

Failure –No Display Solution: –Case 1. –Test the resistance of C903~C911 by using multi- meter,the value should be infinity. Replace the capacitor which has any Resistance. C903 C911

GSM Cell Phone –Case 2. Re-solder the soldering points of LCD Module. Replace LCD Module if the soldering points are all right. LCD Module

GSM Cell Phone J1 - Case 3. Check the soldering points and connection of J1 and J901 connectors. Check the circuit trace on UIF board

Failure –Dark display Black line Short of lines Unstable brightness Solution: –LCD defect Please replace LCD –In case of dark display, replace LCD in advance, if it does not help, then replace U48 U48

Failure –No Back Light Solution : –Replace the LED which doesnt light up if only part of LEDs fail. –All of LEDs fail,please check the soldering points of J1. –Check the circuit trace on UIF board. J1 LED

II-4. Transmission & Receiving failure (Refer to Remark)

GSM Cell Phone Failure - Receiving signal failure Solution - Case 1. Check the soldering points of Antenna Spring and around ant spring. ANT Spring

GSM Cell Phone - Case 2. Check the signals SERDA, SERCK on U31 pin 29,30 and U19 Pin 12,13. If there is no SERDA and SERCK, the defect could be caused by U19, U31 or U1. U31 U19

-Case 3. Check the soldering points of U23 and U31(W3020). - Replace U23,U31 if the soldering checks good. U23

GSM Cell Phone - Case 4. Check the VCO output (540MHz) from pin6 of U42 and UHF VCO output from U19. Replace U42 or U19 if there is no VCO or UHF VCO output. U42 U19

Failure - Transmission signal failure Solution - Case1. Check the soldering of U23,U9,U32. - Replace U23,U9,U32 if the soldering checks good. U23 U32 U9

GSM Cell Phone - Case 2. Check the signals SERDA, SERCK on U31 pin 29,30 and U19 Pin 12,13. If there is no SERDA and SERCK, the defect could be caused by U19, U31 or U1. U31 U19

GSM Cell Phone - Case 3. Check the VCO output (540MHz) from pin6 of U42 and UHF VCO output from U19. Replace U42 or U19 if there is no VCO or UHF VCO output. U42 U19

Failure - Cant communicate Solution: - Case 1. Upgrade Software to the latest version. - Calibration once again.

GSM Cell Phone - Case 2. Check the signals TDO, TCK, TDI, TMS. Replace U1 or U15 if there are no TDO, TCK, TDI, TMS signals.. U15

Remark Re-calibration will be required after replacing the components in RF section. Components U23 U9 U32 and U31 are the focal point of RF part. This revision only indicates the typical failure for repairing reference.

II-5. Other function failure

Failure : –Vibrator function failure Solution : –Case 1. –Check the wire of Vibrator if its ok. –Arrange the wire carefully when assemble main board. –Check the Vibrator if is fixed on lower case. Vibrator wire

GSM Cell Phone -Case 2. Use multi-matter to check the resister R Replace R338 if its resistance too high. R338

Failure : –Key function failure Solution : –Check the soldering points around socket J1 –Check if there is any dirt flux on the surface of UIF board. J1 UIF board

Failure –Weak Buzzer sound Solution: –Replace Buzzer. Buzzer

Failure –No Buzzer sound Solution: –Check the soldering of J1. –Check the trace insulator around screw hole on the UIF board. J1 UIF Board

Failure –Insert card message Solution: –Replace C6 capacitor if it has any resistnce. –If C6 is fine, please replace U11 C6 U11

Failure –Clock stop Solution: –Check X1 if soldering is ok. –Replace X1crystal if there is no 32KHz frequency output. X1

GSM Cell Phone Failure : - Clock time is not correct Solution : - Check the backup battery BT1. BT1

Failure –Key light failure Solution: –Parts of LEDs go out please replace new LED –All of LEDs fail,please check both of J1 and UIF board if its cold soldering or trace broken. LED