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Mobile Phone Hardware Testing and Repairing

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This article covers mobile phone hardware testing and repairing. It describes the major hardware components in a mobile phone and explores common faults along with their solutions.

The use of mobile phones has increased dramatically, driven by the availability of more affordable devices. We now use them for voice calls, text messages, email, internet access, photography, banking, and much more. Mobile phones come in various designs like bar phones, flip phones, slider phones, and touchscreen phones. While the hardware layout may differ slightly between these, the core components and their functions remain largely consistent. This article will delve into the typical components found in a mobile phone, their functions, and how to approach common hardware faults.

Mobile Phone Hardware Components

Here’s a look at the major components within a typical mobile phone:

Mobile phone hardware components Figure-1: Major components in a mobile phone

The table below lists common mobile phone components and their functions:

Mobile ComponentsDescription
Display ScreenVarious display types exist, with LCD being the most common. They display data and are controlled by the CPU.
KeypadUsed by the user to input data. It is interfaced with the CPU. Smartphones often use a soft keypad displayed on the screen in a QWERTY format.
EarpieceConverts electrical signals into sound, allowing you to hear calls.
MouthpieceConverts sound into electrical signals, allowing you to speak during calls.
BatteryProvides the power source for all the components within the mobile phone.
Power ICTakes power from the battery and distributes it to the various hardware components of the phone.
Power SwitchUsed to turn the mobile phone ON or OFF.
Charging ICDerives current from the charger to charge the phone’s battery.
Flash ICStores the phone’s operating system, applications, and other software programs.
CPUThe processor, which is responsible for controlling all the phone’s functions.
AntennaConnects the phone to cellular networks (GSM/CDMA/LTE) for voice and data services. It transmits and receives radio frequencies.

Mobile Phone Repairing Essentials

To repair and troubleshoot mobile phones effectively, you’ll need the right tools, skills, and knowledge:

  1. Tools and Equipment: Essential tools include a soldering iron and wire, thinner or cleaner, jumper wire and cutter, screwdrivers, tweezers, a multimeter, and a hot air blower.
  2. Disassembly and Assembly: Familiarity with how to disassemble and reassemble mobile phones is crucial.
  3. Visual Inspection: After disassembly, visually inspect for burned, overheated, or loose/broken components.
  4. Problem Segregation: Narrow down the problem by identifying the root cause and focusing on that issue. A circuit diagram of the mobile phone’s hardware PCB can be helpful for complex diagnostics.
  5. Testing: Use cold testing (resistance measurements without power) and hot testing (voltage/current measurements with power) with a multimeter. Remember that current is measured in series, so you will need to break the circuit to insert your meter.
  6. Software: Modern smartphones often rely heavily on software. For some issues you may need to download the software from the manufacturer and flash it to the phone. Use a USB cable to connect your phone to your computer and be sure to download from a reputable source.

Major Faults and Solutions

Here’s a table of common faults found in mobile phones, along with potential solutions:

Common Hardware FaultDescriptionSolution
Battery charging issues• Battery does not charge.
• Mobile gets hot when connected to the charger.		• First, determine if the problem lies with the battery or the charger. Replace each with a working unit.
• If the charger is the issue, test its voltage using a multimeter (typically 5-7V). Test the battery voltage as well.
• If both charger and battery work, the charging IC on the phone is the likely problem. It needs to be tested and replaced if faulty.
Network issues• No network.
• Weak network signal.		• First, try moving to an open area to rule out signal obstruction.
• Manually search for network operators and select your provider.
• If the problem continues, troubleshoot the respective network IC. Other nearby ICs like the crystal oscillator, power IC, or CPU could be at fault, so check each and replace if necessary.
OverheatingPhone overheats due to hardware or software issues.• Identify if a specific application is causing the issue.
• Running multiple apps simultaneously can overheat phones.
• If these do not appear to be the cause, the mobile phone PCB may be the problem, and should be replaced.
Sound faults• Earpiece/microphone problems.
• Ringer issue.
• Vibration issues. Common issues: low or no sound.		• Check speaker volume levels in the phone settings.
• Replace the audio IC or power IC (UEM).
• Change the ringer, buzzer, or IHF speaker.
Display faultDisplay not working.• First, check the software display settings (e.g., brightness).
• Check the display IC located between the display and CPU.
Touchscreen issues• Touchscreen unresponsive.
• Some keys work, some don’t.
• Half the screen is not functional.		• Check touch screen sensors.
• Replace the touchscreen and check again.
• Replace the PDA or screen touch IC.
• As the touchscreen is controlled by the CPU, check the interface between them.
Keypad issues• Keys do not work.
• Keys require excessive pressure to activate.		• Check if the keypad is correctly attached to the motherboard. Check the key contacts.
• If required, replace the keypad, keypad IC or interface IC.
SIM issues• Insert SIM message.
• Invalid SIM message.		• Check if the SIM is valid and working, try another SIM if necessary.
• If the SIM IC gets heated, replace it.
• Check the SIM connector and SIM position.
WiFi/internet problems• Internet not available.
• Low WiFi signal.
• WiFi does not enable.		• Ensure that the WiFi security password and username are valid.
• Check that the WiFi AP/router is powered on and the antenna is attached properly.
• If the issue continues, check the WiFi IC on the mobile phone’s PCB.
Software/app fault• Phone does not power on.
• Phone in test mode.
• Phone is not charging.
• Prompts the user to contact the service provider.
• Phone freezes.		• Download and install the Operating System.
• Determine if a specific application is causing the issue. Reinstall if necessary.
• Reset the phone to its original factory settings.

This article serves as a helpful guide for mobile phone hardware testing and repair.