LG-200 Series Repair Trouble Shooting Level I ~ III

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LG-200 Series
Repair Trouble Shooting

Level I III
VER.1.0
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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 13)
• Applicability
• This trouble shooting is only applicable to
  professional engineer for repairing mobile phone.

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II.Contents

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

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II-1. Power Supply Failure
5

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

J5
6

• 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
7

• 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
8

• 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
9

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

U32
U9
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• 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)
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• 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
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II-2. Voice function failure
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Failure - Microphone voice failure. Solution
Case 1. Replace a new Microphone and try again.
Microphone
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• Case 2.
• Test the resistance of C18 capacitor by using
  multi-meter.
• Replace C18 if there is any resistance has
  been detected.

C18
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• Case 3.
• The fault could be caused by DSP U1 coldering or
  defedt.

U1 (DSP)
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• Failure
• Hand free function failure
• Solution
• J5 Cold soldering. Please re-solder again.
• J5 broken, please replace connector J5.

J5
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Failure - No receiving sound( Earpiece). Solutio
n
Replace a new Receiver and try again.
Receiver
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II-3. Display function failure
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• Failure
• LCD broken
• Solution
• - Replace whole LCD modular.
• - Soldering the LCD modular with care.
• LCM Broken should be the customer damaged.

LCM
23

• Failure
• No Display
• Solution
• Case 1.
• Test the resistance of C903C911 by using
  multi-meter,the value should be infinity.
  Replace the capacitor which has any Resistance.

C911
C903
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• Case 2.
• Re-solder the soldering points of LCD Module.
• Replace LCD Module if the soldering points are
  all right.

LCD Module
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- Case 3. Check the soldering points and
connection of J1 and J901 connectors.

Check the circuit trace on UIF board
J1
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• 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
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• 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.

LED
J1
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II-4. Transmission Receiving failure

(Refer to Remark)
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• Failure
• - Receiving signal failure
• Solution
• - Case 1.
• Check the soldering points of Antenna Spring
  and around ant spring.

ANT Spring
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- 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.
U19
U31
31

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

U23
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- 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.
U19
U42
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• Failure
• - Transmission signal failure
• Solution
• - Case1.
• Check the soldering of U23,U9,U32.
• - Replace U23,U9,U32 if the soldering checks
  good.

U32
U9
U23
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- 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.
U19
U31
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- 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.
U19
U42
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• Failure
• - Cant communicate
• Solution
• - Case 1.
• Upgrade Software to the latest version.
• - Calibration once again.

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

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II-5. Other function failure
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• 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
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• -Case 2.
• Use multi-matter to check the resister R338.
• - Replace R338 if its resistance too high.

R338
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• 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
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• Failure
• Weak Buzzer sound
• Solution
• Replace Buzzer.

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

UIF Board
J1
45

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

C6
U11
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• Failure
• Clock stop
• Solution
• Check X1 if soldering is ok.
• Replace X1crystal if there is no 32KHz frequency
  output.

X1
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Failure - Clock time is not correct Solution
- Check the backup battery BT1.
BT1
48

• 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