Mobile Repairing

MOBILE TROUBLESHOOTING By: Nishant Sharma

My Project My project “Mobile Troubleshooting” is about learning of some basic concepts of mobile phone and having some knowledge about troubleshooting those devices. For having some basic knowledge of devices, I took help from an expert who repairs mobile phone. I also gained some knowledge about how to use the basic devices like Ammeter, Multimeter etc which are frequently used for mobile troubleshooting.

Basic operations of a mobile phone Basic components of a mobile are: 1) Battery: Battery is just a power source of a mobile phone. 2) Keypad Keypad (push button) is an input device of a mobile phone used to give input’s too mobile and is used by users for dialling numbers and for sending SMS.

 Now a day’s mobile phones are having touchpad where there are no keys but a user can give input by just touching the screen. Basically it is of two types: type: In which touch works on the basis of changing of resistance which got 1) Resistive type: changed when we touch the screen. type: In this type when a user touches the screen the capacitance of that 2) Capacitive type: part got changed and hence it works according to those changes.

3) Speaker Speaker is an output device of a mobile phone, which is used for giving hearing outputs. In an ordinary mobile there are two speakers:

1) Earpiece: just a small speaker which doesn’t produce loud sounds. 2) Ringer: A speaker capable of producing loud sounds. (Generally a separate ringer IC is used for a ringer speaker)

4) Display: Display is also an output device of mobile phone used for giving visual outputs. Mainly different phones have different display size.

5) Chips and IC’s In a mobile there are generally large numbers of chips and IC’s like CPU and IC’s are of  many kinds depending on their device.

Some of them are: Power IC, Frequency Filter IC, Ringer IC etc.

6) PCB (Printed Circuit Board) PCB is printed circuit board which is a non conductive hard platform of a Mobile where all the devices are assembled and the reason it is called a circuit board is that it have connections on its surface.

 Now days’s, there are different types of PCB, main are TWO layer PCB and THREE layer PCB. A TWO layer PCB have circuits printed on its upper and lower side whereas a THREE layer PCB have an advantage of having printed circuit also in the middle.

Mobile Reparing Tools Some basic tools used for mobile repairing are: 1) Multi Meter: (VOM) is an measuring instrument. A multimeter have features like measuring voltage, current, resistance and continuity. It is used for measuring correctness of  the devices.

2) Soldering Iron: Soldering Iron is used for connecting the broken connections or wires. For soldering one always need a Soldering Wire and sometimes Solder paste (It is used to connect the leads of IC packages to attachment points in the circuit PCB)

3) Toolkit: One will always require a perfect toolkit for repairing a Mobile phone. An ideal toolkit at least contains some screw drivers (different sizes), holders, multimeter, etc.

Some Common faults : 1) Power Supply: This is a problem when mobile phone is not getting proper power supply. Some common reason are:  

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Battery Dead May be the changed battery may have the same voltage value but different current value OR vice-versa Shorting somewhere which also leads too same problem

The best way to correct such a problem is first to check for the correctness of the battery and if it is correct then check for the shorting part.

2) Speaker Problem: This is a common problem that speaker is not working. For this we first check for the correctness of the Speaker with the help of the multimeter. We set the multimeter to continuity direction and check the speaker’s both ends for both directions.

If we get Beep sounds in both the direction that means that the Speaker is correct, but if we don’t get Beep sound from both sides then it means that the speaker is not working. And then we have to change the speaker with a new one.

3) MIC Problem: Another common problem in mobile phones is MIC NOT working. For testing a MIC, we again set the multimeter to continuity or 20 V and then check the MIC’s both ends in both direction. Then we must get a beep from other side and not from its reverse direction , if it is so that means that MIC is correct and problem is somewhere else. Otherwise we have to change the MIC with a new Working one.

4) Keypad problem: Sometimes we found that some keys of a keypad doesn’t work. For this we first check that on the buttons where it got clicked there must not be any carbon if  it is there we must remove that and check then. Otherwise we check continuity of the circuit related to the keys.

THE PHONE I TROUBLESHOOT Nokia 1112 Main Problems: This phone was went in water a month ago and its MIC and speaker were not working at all and the display was also not clear on some part of the screen and some keys are also not working. Repairing: First of all I took started open it. I opened with very care because if we press the screw while loosening then it may result in cracks in PCB or any other fault. After opening first of all I opened the speaker and check its correctness as mentioned above. There i found that it was only giving beep sound in one direction. This means that Speaker was dead.And when I put that speaker out I found that It was corroded. Then I checked for the MIC that it was giving beeps in both direction. This means that it was also dead. After that I checked for the keys and I found that there was carbon on those points so I cleaned it and after that I washed it with diluter and then it was working properly. And then I checked for the Display problem so I found that there was water in the display. And also some connections were got loosened. I took a small soldering Iron and solder it with the help soldering wire. After this I purchased A speaker and a MIC and test both of them and they are working properly. Then I put them in their places. But even then the loudspeaker wasn’t working. So I again open the Mobile and this time I started testing for the

connection of the Ringer speaker. There the two possibilities are that may be the CPU is not working of the ringer IC is not working or may be the connection is broken somewhere. But CPU is all right as the mobile was overall working properly. And then I opened the cover of the protected region and checked the connections with the help of a multimeter by setting it to Continuity. And I found that all the connection were right. So I checked for the upper part where Speaker is actually connected, and that part was also continuous. So, I concluded that the ringer IC was NOT working .

I can’t correct it because it more that basic concepts. OUTCOME OF THE PROJECT I opened a mobile and troubleshoot all the basic parts of it like Speaker, Mic, keypad, Display