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How to Check Parts of a Mobile Phone for Fault

When doing mobile phone repairing, you will often need to check parts such as speaker, ringer, vibrator, coil, boost coin, On / Off Switch, Antenna Switch, RX Filter, PFO, BSI, Network IC, VCO, Audio IC, Power IC, RTC, Charging IC, CPU, R22, Microphone Interface, Bluetooth IC, Flash IC, RAM, Logic IC, UEM etc.

In most cases, only card level parts of a mobile cell phone are checked for fault and then repaired or replaced with a new one. Card level parts of a mobile cell phone include ringer, speaker, microphone, vibrator, LED, charging connector, headphone connector, data cable connector, battery, battery connector, SIM card, SIM card connector, memory card, memory card connector, camera, camera connector, keypad button, keypad connector, ON / OFF Switch, Display, Display connector, Internal antenna and PDA.

Chip level small parts of a mobile phone that include small electronics components like capacitors, resistor, diode, coil, boost coil, coupler, regulator, transistors, are rarely or not tested for fault. In case there is any fault in the track of the Mobile Phone PCB then it is solved or fixed by jumper.

Mobile Phone Tools and Equipment Needed to Check Parts of a Mobile Phone for Fault are:

How to Check Parts of a Mobile Phone for Fault

  1. Ringer: To check if the ringer of a mobile phone is faulty or damaged,
    Multimeter for Mobile Phone Repairing

    Multimeter for Mobile Phone Repairing

    keep the multimeter in buzzer mode and check the ringer. Value must be between 8 to 10 Ohms. If the value is between this range then the ringer is good and does not need replacement. If the value on multimeter is 4-5 or 12-14 then change the ringer.

  2. Vibrator or Motor: Keep the multimeter in Buzzer Mode and check the vibrator, Value must be 8 to 16 Ohms. If the value is between 8-16 Ohms then the vibrator is good. Otherwise change it.
  3. Speaker or Earpiece: Check the speaker / earpiece with a multimeter on Buzzer mode. Value must be in the range of 25 to 35 Ohms. If the value is in this range then the speaker / earpiece is OK and need not be changed. Otherwise, change the speaker / earpiece.
  4. Microphone or Mic: Keep the multimeter in buzzer mode and check the microphone. Value reading on the multimeter must be in the range of 600 to 1800 Ohms. There will also be a Beep or Buzz sound from the multimeter. NOTE:  Please note that only one side of the microphone will show value. If we check by reversing the Red and Black Probes / Test Leads of the multimeter and check the microphone then there will be no value.
  5. Coil: Check it with a multimeter on Buzzer Mode. If it is good then it the multimeter will give a Beep or Buzz sound. If there is no sound then the coil is faulty. Replace it with a new one.
  6. Resistor or Resistance: Check it with a multimeter on Buzzer Mode. If it is good then the multimeter will give a Beep or Buzz sound. If there is no sound then the resistor is faulty. Replace it with a new one.
  7. Capacitor: Check it with a multimeter on Buzzer Mode. If it is good then the multimeter will NOT give any Beep or Buzz sound. If there is sound then the capacitor is faulty. Replace it with a new one.
  8. Diode: Check it with a multimeter on Buzzer Mode. If it is good then the multimeter will NOT give any Beep or Buzz sound. If there is sound then the diode is faulty. Replace it with a new one.
  9. LED: Keep the multimeter in Buzzer mode and check the LED. If the LED is good then they will glow otherwise not.
  10. Coil and Boosting Coil: Check for continuity. If there is continuity then the coil or the Boost Coil is good otherwise it is faulty.
  11. Keypad: Keep the multimeter on Buzzer mode and check Rows and Columns or the Key Pad. If there is Beep or Buzz sound from the multimeter then Keypad is ok, otherwise it is faulty.
  12. Battery Connector: Keep multimeter on 20V DC and check. Value must be 1.5 to 3.5 V DC.
  13. Battery: Check voltage with a multimeter. Keep multimeter on 20V DC and check. Value must be 3.7 V DC or above.
  14. ON / OFF Switch: Check voltage with a multimeter. Keep multimeter on 20V DC and check. Value must be between 2.5 to 3.7 V DC.
  15. Network IC: Use a Analog DC Power Supply to check Network IC. Switch ON DC Power Supply and call any number from your mobile phone. The Needle of the DC Ampere will start moving. This shows that the Network IC is OK and not fault.
  16. Power IC and CPU: Adjust voltage of the DC Power Supply to 4.2. Place the Red Probe / Test Lead of the DC Power Power Supply to the “+” of the Battery Connector of the mobile phone and the Black Probe / Test Lead to “-“. If DC Ampere is over 6 then Power IC or CPU is damaged. Check by replacing Power IC and the CPU one by one.
  17. If there is no movement of the Ampere Needle of the Power Supply then the Battery connector, On / OFF Switch Track, RTC or Network Crystal is damaged. Give heat to these components using hot air blower. If the problem is not solved then check by replacing them one by one.
  18. If the Ampere Needle fluctuates below 2 ten there could be problem with software or RTC (Real Time Clock).
  19. If the Ampere needle stands at some fixed point then there is problem with the Flash IC.
  20. If there is beep sound from the DC Power Supply then there is problem with “+” and “-” or the mobile handset is short.

PS: When checking a faulty mobile phone with DC Power supply, connect the Red Probe to “+” and Black Probe to “-” of the Battery Connector of the Mobile Phone.

DC Power Supply

DC Power Supply

Notes:

  • Most mobile phone repair people and technician check only above parts of any mobile phone to solve hardware problems.
  • All other parts including electronic components and ICs are generally not checked for fault. There is no good sure test for these parts. The problem is either solved by jumper or by trial and error (check by replacement).

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Santosh Das is an Electronics Engineer, Blogger, Young Entrepreneur and Founder of this Mobile Phone Repairing Website. Santosh possesses vast experience in the field of electronics, telecommunication, Soldering, SMT, ESD Safety, and electronics manufacturing tools, equipment and consumables. Santosh left his job in 2014 and started his own Private Limited Company that deals and supplies PCB Assembly and Rework Tools, Equipment and Consumables. Keep visiting for daily dose of Tips and Tutorials.

43 Responses to How to Check Parts of a Mobile Phone for Fault

  1. salvesanyog@gmail.com' sanyog salve says:

    Hi sir
    I like this site and i learnt so many things .
    and i m very great full to you.

  2. mbake2006@yahoo.com' modou says:

    this offers useful guide to beginners in cellphone repair.we would be glad if the info is more comprehensive. thanks a lot

  3. rajuchoudhary.2015@gmail.com' Raju Jat says:

    I love This site

  4. yemane3@gmail.com' yemane says:

    you done it best thanks!!

  5. Eyayu.g@gmail.com' Eyayu says:

    Very very thanks it is great knowledge in this site .

  6. Dotcomlegend@gmail.com' James Imaga says:

    Hi,I’m highly impressed by your tutorials they’re are top class and easy to understand and moreso highly factual I want to say its one of the best I’ve come across on mobile phone repairing tech.Keep the good work up.Please can you send me some tutorials on mobile phone jumper setting I’ll be very grateful.Thanks.U can use my email to reach me.

  7. safsmiles@yahoo.com' safwan says:

    hi ray,

    is there any institute of urs where i can learn mobile repairing course

    thnks

  8. 21sushilkumar@gmail.com' Sushil Kumar says:

    good site.I like.

    thanks

  9. rajendersingh162@gmail.com' raj says:

    is ur collage in jalandhar punjab state thanks

  10. hero_bd59@yahoo.com' Roki says:

    My mobile phone is turning off. when headphone jack through 9v dc supply.whats the problem.
    thank !!!

  11. aks9440088000@gmail.com' A karthik Srinivas says:

    Very useful tutorials… Thanks a lot…

  12. sureshgurule@rediff.com' Suresh says:

    Da,

    I have Karbon a21 the power on mother board is OK but no display. I changed the display but still it is blank and the display is getting hot at the bottom. What to do now?

    • Santosh Das says:

      There is some short in the phone. The phone Karbon A21 has faults in its design and manufacturing. This is a common problem in all A21. It is better to get rid of the phone and buy a new one. Any money you spend on its repairing will be waste. Never trust Karbon.

  13. thegrimboy00@gmail.com' sanjay says:

    Cant hear callers voice in mobile earpiece ,but can hear in loud speaker what is the problem and how to rectify

  14. sayyedgemstone44@gmail.com' Sayyed Ismail says:

    Hello thanks for detail this is very help full for me

  15. bakle2626@gmail.com' amit says:

    My nokia mobile problem
    “Invalid sim” how to problem solv

  16. bakle2626@gmail.com' amit says:

    Yes i reset the phone and other sim check but not ok

  17. bakle2626@gmail.com' amit says:

    Tellme. How solv the problem

  18. bakle2626@gmail.com' amit says:

    How to solv problem

  19. kamalnathr2010@gmail.com' kamal says:

    Iphone 3g heating problem near power control ic, check the capacitor as said beeps ?, battery charging connector on logicboard shows 0.7 v on charger plugged , charging port Ok .pls help

  20. funnybones@sky.com' Fred says:

    Hi, Great site. My Samsung Galaxy Y. switches on but will not get past opening flash and SAMSUNG letters will not go beyond this and when I press off/on with operation key it just goes back to same. Any ideas.
    Thanks,
    Fred

    • Santosh Das says:

      Reset the phone and check. It the problem is not solved by flashing then you may have to reload the software.

  21. manojgoyal5385@gmail.com' manoj goyal says:

    Can u explain the cool testing,hot testing,parallel track and series track

  22. bakle2626@gmail.com' amit says:

    My nokia c1 is dead on/off swicht voltag 1.43v how to solv

  23. aikom4real@ymail.com' Murphy martins says:

    My blackberry turch1 phone is draining fast the battery., pls what’s your advice.?

  24. bakle2626@gmail.com' amit says:

    Hi samsung v3303 no network problem

  25. mtrendzpc@gmail.com' H.Murugan (mtrendz) says:

    iam not a technician but i visit this this web page. Now i would like to achive a tech..
    very very thanks to all.this articles very usefull…….

  26. rahulsona64@gmail.com' rahul says:

    this is a great site,

  27. YORDY83@JMAIL.COM' YORDANOS says:

    THANKS FOR ALL

  28. mzafarpathan@gmail.com' raheem says:

    Sir how to check series current in tablet

  29. jitprakash81@gmail.com' jitprakash says:

    jai bigyana…

  30. yogendra12garg@gmail.com' yogendra garg says:

    Sir mujhe mobile ki pcb track check kaise krte fuse coil capcatrs digital mieter me kiase check krte hai video chahiye

  31. saeedahmad272@gmail.com' .saeed ahmed says:

    Aoa Sir very nice l like it. Sir plz send me Iphone like 4 4s 5 5s repairing tips to my this Gmail address plz.

  32. saeedahmad272@gmail.com' .saeed ahmed says:

    Hi sir where r u?

  33. htay.shutieyin1983@gmail.com' thaunghtay says:

    thank you

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