Download 2015_COL_Repair-Maintenance-Mobile-Cell-Phones.pdf PDF

File Size1.2 MB
Total Pages49
Document Text Contents
Page 1



Page 2

Mobile Phone Repair and Maintenance

Page 2


This course was drafted at a Commonwealth of Learning workshop in Nairobi, Kenya in October 2013.
The participants worked with Professor Fred Lockwood to test the rapid course development model.

We appreciate all the course authors who provided relevant information during the design and
development of this course. In particular, we want to thank the following:

1. Kamau Charles Masai Technical Training Institute

2. Muasya Douglas Coast Institute of Technology: Lead Author

3. Mugure Tabitha Thika Technical Training Institute

4. Njoroge Stella Masai Technical Training Institute

5. Ochuma Johnstone Kenya Institute of Curriculum Development

6. Wanjala Antony Coast Institute of Technology

Instructional Design: Joan Mutero

Layout & Graphics: Anthony Okuku

Commonwealth of Learning
© 2015 Commonwealth of Learning

This publication is made available under a Creative Commons Attribution-ShareAlike 4.0 Licence

Page 24

Mobile Phone Repair and Maintenance

Page 24

Steps In Soldering

1. Prepare the following materials:

 Soldering Iron,

 Solder paste

 Long Nose Pliers,

 PCB holder,

 Electronic Components (Resistors, Diode etc.)

2. Plug and pre-heat the soldering iron.
3. Heat both items at the same time by applying the soldering iron to the

copper pad and the component lead.
4. Continue heating and apply a few millimeters of solder. Remove the iron and

allow the solder joint to cool naturally.
5. It only takes a second or two to make the perfect joint, which should appear



Desoldering is the removal of solder and components from a printed circuit
board for troubleshooting, repair, replacement, and salvage.

Figure 28: Desoldering

Steps in desoldering

1. Use a solder wick (finely braided copper) to wick away excess solder from a de-

soldered connection.
2. Apply the solder wick and use the soldering iron to the de-soldered

connection. The solder wick will draw the excess solder off the PCB pad.

Testing a phone using a multimeter

We hope you still remember that a multimeter is a device that is used to measure
the voltage, current and resistance of various components of a mobile phone. Figure
29 below shows the various parts of a multimeter

Page 25

Mobile Phone Repair and Maintenance

Page 25

Figure 29: Parts of a multimeter

We shall now discuss how to measure resistance, voltage and current using a

a) Measuring Resistance

To measure resistance follow these steps:

1. Plug your red and black probes into the
appropriate sockets on your multimeter.

2. Choose the appropriate resistance
measurement setting on your millimeter’s

3. Hold the probes against the resistor.
4. Check the resistor value on the display.

Figure 30: Using a Multimeter

b) Measuring voltage

Testing for proper supply voltage is usually the first step when troubleshooting a
circuit. To measure voltage you should follow these steps:

1. Select V~ (ac) or V (dc), as desired.
2. Plug the black test probe into the COM input jack. Plug the red test probe

into the V input jack.
3. If the DMM has a manual range only, select the highest range so as not to

overload the input.

Red Probe

Function and
Range switch


Black Probe

VΩ m A jack

Common Jack

Take Note: Always turn off the power supply to your circuit before
measuring resistance.

Page 48

Mobile Phone Repair and Maintenance

Page 48

7. State any six types of SIM faults


8. Name any six Micro SD Card /MMC faults


9 Complete the table below by writing the possible causes of the phone faults in

the left hand column.

No: Phone problem Possible cause

1. Unable to send SMS

2. Only incoming call

3. Security code

4. No signal

5. SIM locked message

6. Contact service provider

Software Faults

10. List any five phone software faults.


Page 49

Mobile Phone Repair and Maintenance

Page 49

Hardware faults


No: Phone problem Possible cause

1. Unable to send SMS No service centre number

2. Only incoming call Call barring enabled

3. Security code Wrong security code

4. No signal Service provider not selected

5. SIM locked message Wrong PIN/ SIM lock code

6. Contact service provider
Sim card blocked by service

Software faults

i Display
ii No signal
iii Dead set
iv Test mode
v Not charging
vi Contact service provider
vii Hanging
viii Auto restart
ix White screen
x Ring out on its own
xi Select options on its own
xii Run extremely low
xiii Auto off

Similer Documents