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Complete Mobile Repairing Guide

Logo.pngHello! All members and visitors. Today i want share anything with you. That i know about Cell phone Repairing. If you are searching good based blogger for learn how to repair cell phone at home the you are right here. Happy to say after a long waited i have plan for teaching about cell phone repairing. Hope you enjoy these some tricks and techniques. As you know my wish, "Provide you a rich and unique contents" As my best knowledge base. I strongly request you to comments about my work. For improve my job i appreciate your suggestion. Thank you for visit "Let we stat"

Learn At Home, Complete Mobile Repairing now so easy.

Before start our work i want share what kind of tools you have required for cell phone repairing. If you have a shop then no need any extra tools. But for new student must have access the following tools for testing and tracing cell phone faults.
  1. Solder wire / jumper wire and and heat gun with soldering element
  2. Board griper and tools kit 
  3. Ct or petrol, Old cell phone PCB and some of accessories .e.g. charger, data cables software flashing devices, computer and internet
  4. Old cell phone dead motherboards for some parts replacing e.g. resistance/capacitor
  5. In the parts box basic most running parts of mobile phone e.g. mic,battery terminal,display(LCD),ringer,speaker,battery connector,charging base,sim jacket
  6. For Copying memory card, You need card reader

 Cell Phone Categories by series are following:

In the market many cell phone models comes with different names. Every brand are labeled e.g. Nokia,Samsung, Qmobile etc. After the cell phone name on front / behind the batter / on the inner there have model number e.g. Samsung Galaxy j-700 f. Every cell phone is comes in market by series, Some of most common series are following:

S-40 Series (Without java and application)

Some have java but many are without java. (Java is the software based facility that provide play games or software's) For example Nokia 1100,1110,1212,c-1 and other small price handset are comes in this categorize.

S-60 Series (With java or without java) 

After success s-40 series Nokia have lounge s-60 series with more rams and user friendly browsing software. Nokia is the one of the best for easy and power full user friendly software, As known the Nokia logo hand set is the sign of quality and guaranty. In this categorize some most popular handset from Nokia company comes in past e.g. Nokia C-5, C-3, x-2-02 etc. (In these latest brands are comes with WiFi)wireless connection.

X series (Implicated WiFi, 3-G, 4G and Touch panel)

Is the series with WiFi and internet explorer for communication friendly and speedy some have 3-G or 4-G band.

Windows Series (Implicated WiFi, 3-G, 4G and Touch panel)

Latest by Nokia Company. Nokia introduce Windows cell phone with ios support implicated. Nokia Lumia is the best in this categorizes. Nokia 430,720 are my fave rte.

Android Series (Implicated WiFi, 3-G, 4G and Touch panel)

In these days this series is no-1 in all around the world. Many application are available and this series is touch and non touch used in many communicative devices. Tab, Note, Cell phone, Television, Camera, and many latest devices comes in the market with android version. 

Understand, CELL PHONE PCB

Home for electronics parts, Where the all parts are paired by tree. There on every PCB or motherboard many parts are by series connected each others familiar. They called integrated in the following categorizes:
  1. Verb (Major parts on PCB) Example: IC (Integrated circuit) is the verb part of PCB
  2. Non verb (Helping Parts for major parts on PCB)Example:Resistance and capacitor are the helping parts for IC (Integrated circuit) on PCB
  3. Fuse and jumpers are for safety use in every electronics devices
Every Electronics and electric device use a board for home Parts to connect each others. On the board connection plate should help by lines to connect as a series all parts. Fiber and cotton mixer plate, Assembled for long life and hardness to get non polar polarity for connection plate.
  • Resistance (Most common use in every electronics/electric devices)
Every cell phone use current from battery as a power source. Battery current ampere and volts are important for cell phone. On the motherboard of cell phone there many parts which are working by series. Some have need 3 to 4 volts and some have need just so low voltages. Some frequency stages can use resistance for resist. As the name of Resist, From high to low convert parts on cell phone motherboard called resistance. In the Television the value of color coding may help to find expect value of  resistance. Here are color coding for resistance:Black,Brown,Red,Orange,Green,Blue,Gray,White.

How it should work.

Up Numbering can not help in micro parts like as resistance or capacitor, There on micro parts the only one color can help for resistance, BLACK is the symbol for resistance. Size of Resistance should control capacity. So the main thing to understood in this case, We have 3.7 volts from battery. We need low volts from 3.7 to 1.5 to supply some major parts, e.g. IC. To solve this issue every cell phone and electronics devices use Resistance. When we check any resistance on the multi check meter there are dial shows some ratings about resist. 

Capacitor (This is the most commonly used in every electronics/electronic devices)

Capacitor can store current for some moments, Some time during first startup cell phone or any device need full power to serve there work. For example Cell phone is powering on and searching signals and found every parts on PCB, There is full bright on display some or many applications are tuning together at startup. The all capacity of used for current is very high. 

More at this topic.

You can check on auto voltage supply regulator display the pixel of used power supply are gone to 69 or above points. But when all processing of cell phone should complete and display lights are off from LCD and Keypad. The handset is off line and there on supply display show very low current in use. Cause for that the some very essential processing is running but most of the other processing should finished for max battery timing automatically. At the testing pros Capacitor there have no rating for long time show a dial pad on multimeter.
So after read all summary about capacitors, Now we can collect some information to find on cell phone motherboard. Brown or white or black color is the symbol for capacitor. Brown is used for Stored current. and others colors are for frequency cycle control's. So the last word about capacitors are used for filtering and storing currents in every electronics and electric devices. In the cell phone every parts are micro categorizes.
  • Fuse (This is the most commonly used in every electronics/electronic devices)
In faulty this parts, "FUSE" the device completely dead and there is no response on power in from fuse one side to other side. For the safety of the device, the Fuse is the connection of positive volts supply to a board. As a wire the fuse system is used most  commonly. For example to understand:
  1. From the main supply, Battery / charger is over current the fuse may have harm.
  2. From the water or rain shortage current, Fuse may have harm.
  3. From the old water damaged handset, Fuse may have harm.
  4. From the opposite connection of current e.g. negative probe connected on positive current, Fuse may have harm and device getting dead.
  5. From the shorted parts of cell phone, Fuse may have harm.
  • Resistance (most commonly used in every electronics/electronic devices)
For saving the energy, This parts is the most commonly used in every device of electronics. On the device motherboard there are many parts with series and parallel connected each other one by one. The all parts of a motherboard have a different rating of a voltages. Their on battery terminal the voltages of rating 3.7 volts but the IC or transistor need an 1.5 volts, To solve this problem the resistance used is very common in positive or negative points.
  1. Resistance should not boost any current from in to out points.
  2. Resistance can gain only high to low current.
  3. Resistance is the connection part of the pcb from one to another point.
  4. Resistance rating is by size and colour valuable.
  5. In condition of faulty this part hande set may have faulty.
  • Transistor (most commonly used in every electronics/electronic devices)
Base, Emitter and collector are the the legs in the every transistor And the category of PNP,NPN for the following:
  1. PNP (Base,collector,emitter) in this category the positive volts in on base point.
  2. NPN (Collector,base,emitter) in this category the positive volts in on collector point.
It can boost or handle volts and frequency cycles.

IC / Chip (Integrated circuit)

As a name integrated, Many electronics parts in one chip. The major part of cell phone processing unit. from the solid state physics converted some stages of electronics devices e.g. cell phone, camera, tv, computer into a one chip. The processor is a home of multi chips. In every cell phone the main chip (Processor) did not work without some helping parts. See this short menu of the chip for working:
  1. IC: In the cell phone PCB, the major part is a main chip.
  2. Helping parts e.g. resistance,capacitor and transistor are the pre versions of main chip.
  3. Some cell phone used a single chip with build on flashing, signal, Sound etc. but some have independ chip for the signal, flashing and sound etc.
  4. In condition of faulty chip the chip should warm up after few second power on the cell phone. This chip is warming up from the many reasons, Shortage stage of inner in chip / outer on PCB. Example: Main chip is warm up, In the main chip circuit may be the charging,signal,sound or any stage is faulty for cause of warm up the chip. 
  5. From outside the supply is over current, during processing some helping parts may have harm. For the conform is their main chip is faulty, Please be carefull. Trace or check before replace or remove main chip. May be some other reasons are involve to heat up the main chip. e.g. ringer connection are shorted with ground directly.
  6. Power chip, Controller chip for the supply. If faulty, the Handset did not power on or shortage and battery timing is so short.
  7. Signal chip (PA), The signal stage controller chip. If faulty, there is no signal or weak signal in cell phone.
  8. Flashing chip (ROM), Storage drive for cell phone software. if faulty handset did not power on, Some time flashing the lcd and some time hang on LOGO.
  9. Sound chip, Sound controller stage. if faulty there is no sound in ringer.
  10. Bluetooth chip, BT Communication chip controller. If faulty there is no access in search neighbor bluetooth device.
  11. Display chip, Display controller for lcd data. If this chip is faulty, there is no display,scrambled display, white display or blank display on the LCD.
  12. Keypad Chip, Keypad controller chip. If faulty there on keyboard some or all keys are missing. Keypad did not work correctly.

What kind of components that should jumpering by diagrams

Some time the faulty chip /parts are not available in the market. Therefor, With the diagram of jumpering we should make directly jumpers via jumper wire on its connections. Here are the list of those who should jumpering directory of some have without changing with new one.
  1. Keypad chip (Make directly jumper on missing keypad tracks from one by one)
  2. Signal chip (Low signal problem occurred by using the jumpering in some cases)
  3. Fuse (Burning or missing fuse we should directly jumpering from one to another point)
  4. Resistance (We can direct some types of resistance on the PCB)
  5. PCB broken links (From one point to another point we can make a jumper)


When cell phone start hanging, Slow on speed or any application issu. You need to an hard reset your cell phone for the default settings. There are some differents ways to do this action. Here are some hard reset tricks for help to reset your cell phone.

  • Hard reset cell phone from the setting menu (Factory setting)

In the every cell phone have hard reset option with the differents names. In the most common this option found in many cell phones on the setting menu. Found the factory setting, hard reset or reset all data from your cell phone then follow these steps:

  1. Factory setting
  2. Give the password 

Default passwords of many cell phones.

  1. 12345 (Nokia)
  2. 1122,1112,1234,0000,2233 (Android / China)

Hard reset cell phone from the power on (Factory setting)

In the android cell phone the software hard reset option can run from the power on to get the default settings of the cell phone. Some time handset still with pattern lock, Google account lock, Hang on log or slow speed. In this condition you need to hard reset cell phone from the power on. Before start the tricks of numbering here please power off your cell phone. To power off disconnect the battery and insert again. If battery is build in the casing then please power off key press and hold till them the handset getting power off.
  1. Hold on volume up key then press power on button
  2. Hold on volume down key then press power on button
  3. Hold on both volume up and down key then press power on button
  4. Hold on Home plus volume up key then press power on button
  5. Hold on home plus volume down key then press power on button
  • Hard reset cell phone with the flashing device (Factory setting)
In the condition of no access in reset from the software or power on key the last option is "Hard reset" cell phone with the flashing device (Jaf, volcano, flasher) etc. To reset with flashing device you have the direct access to the cell phone flashing memory (ROM) by the RX, TX and battery power points. You can connect the device with your cell phone usb data cable, Device flashing data cable or directly with jumpering on the TX, RX points at the PCB.
  1. Connect your cell  phone with the device data cable
  2. Open flashing software of the device that you have set up in your computer or laptop
  3. Go to the factory default panel and click to continue
Keep in mind during hard reset your cell phone, There are two differents options. One with erase all data and second with only settings. Chose as your need to solve the problem. All Data of the cell phone should eras in complete factory settings. So if the possible for you please before start the job of hard reset "Backup your instant data" and contacts.


Due to rain, water damage or missing broken links are cause of this problem commonly in every cell phone. The broken display solution can solve only with new or working display. But in many time from the troubleshooting of cell phone PCB points i solve these problems:
  1. White display (Change LCD or check lcd connection from the connector)
  2. Blue display (Check connector)
  3. Scrambled display (Check connector from the both sides LCD/PCB)
  4. Blank display (Check connectors, Change LCD)
  5. No lights on the display (Check LED lights, Volts and connection)


When signal stage is faulty the cell phone signal should've gone or low. You can not make a call to another cell phone or during call the sound like as fax machine. In the many cell phone i see the signal baar with the one or two points. In this situation, when the cell phone our range from the tower. There is no signal. Anyway see here are the most commonly signal problem solution:
  1. Low signal (Check antenna)
  2. No signal (Heat, change PA)
  3. Signal OK but call failed (Check RX or TX of signal chip or change signal chip)
Many cell phone signal chip should jumpering, But the long range distance signal problem occurred with jumpering of signal chip. So the first choice to solve this issue please replace the signal chip with new or working.


When insert sim option show on the screen of cell phone after inserting sim in sim tray. This mean this sim stage is faulty of the cell phone. Some time the sim chip is broken cause behind this error but many time i see this problem in sim jacket or connection. So here are the troubleshooting guide for possible solution of insert sim error.
  1. Check / change the sim side and cell phone side connection (Both clean and scratch for the carbonyl issue)
  2. Check the sim jacket points (One point is always ground and in many cell phone the one point is empty) If missing any connection please make jumper.
  3. Check Sim chip (Some time broken or carbonyl chip connection are the major cause) Change the sim controller chip, Heat or make jumpering on it.
Final if no luck, I thing the processing chip points are missing that are routed to the sim controller chip. So be careful in this condition. Before troubleshooting the cell phone. Ask the customer for dead approval. After that heat the main chip or trace the missing jumper from the main chip to sim jacket or sim controller chip points.


Charging error starts in many cell phone from the USB bad connection. There is no option at connect the charger on the screen. But many time i see the charging volts getting wrong rating on the positive point of battery terminal.

Admin and Author Profile.

My name is shahid. I am admin and Author of this blog. I have a 20 years experience in mobile repairing. Earlier updated contents are available free on this blog. To get in touch with us. Please subscribe us. Share it to support us. Hope all above text is helpful. But for the human mixtack. Please feel free to comment or contact us.
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