Screen fixing cell phones Downtown Miami Brickell

Diagnosing and Repairing Mobile Phone Faults Screen fixing cell phones Downtown Miami Brickell

Screen fixing cell phones Downtown Miami Brickell
Screen fixing cell phones Downtown Miami Brickell

The correct diagnosis of mobile cell phone faults is the key to successful and cost effective repair of the phone. Let us start by looking at the skills that you need to have to be able to diagnose and repair a mobile phone.

Skills Needed to Diagnose and Repair a Mobile Phone.  Screen fixing cell phones Downtown Miami Brickell.

Before you can diagnose and repair a phone, there are some skills that you need to learn.

These skills are:

  • Soldering
  • Desoldering
  • Testing using a multimeter
  • Jumper setting

Let us briefly discuss each skill in turn.  Screen fixing cell phones Downtown Miami Brickell.

Soldering. Screen fixing cell phones Downtown Miami Brickell.

Soldering is a process in which two or more metal items are joined together by melting and flowing a filler metal into the joint. The filler metal has a relatively lower melting point.

Steps in Soldering

  1. Prepare the following materials:
  • Soldering Iron,
  • Solder paste
  • Long Nose Pliers,
  • PCB holder,
  • Electronic Components (Resistors, Diode etc.)
  1. Plug and pre-heat the soldering iron. Screen fixing cell phones Downtown Miami Brickell.
  1. Heat both items at the same time by applying the soldering iron to the copper pad and the component lead. Screen fixing cell phones Downtown Miami Brickell.
  1. Continue heating and apply a few millimeters of solder. Remove the iron and allow the solder joint to cool naturally. Screen fixing cell phones Downtown Miami Brickell.
  1. It only takes a second or two to make the perfect joint, which should appear shiny.

Desoldering. Screen fixing cell phones Downtown Miami Brickell.

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

Steps in desoldering

  1. Use a solder wick (finely braided copper) to wick away excess solder from a desoldered connection. Screen fixing cell phones Downtown Miami Brickell.
  1. 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. Screen fixing cell phones Downtown Miami Brickell.

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. Screen fixing cell phones Downtown Miami Brickell.

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

  1. a) Measuring Resistance

To measure resistance, follow these steps:

  1. Plug your red and black probes into the appropriate sockets on your multimeter. Screen fixing cell phones Downtown Miami Brickell.
  2. Choose the appropriate resistance measurement setting on your millimeter’s
  3. Hold the probes against the resistor. Screen fixing cell phones Downtown Miami Brickell.
  4. Check the resistor value on the display.
  1. b) Measuring voltage. Screen fixing cell phones Downtown Miami Brickell.

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

  1. Screen fixing cell phones Downtown Miami Brickell
    Screen fixing cell phones Downtown Miami Brickell

    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. Screen fixing cell phones Downtown Miami Brickell.
  3. If the DMM has a manual range only, select the highest range so as not to overload the input.
  4. Touch the circuit with the tips of the probes. Screen fixing cell phones Downtown Miami Brickell.
  5. Read the number in the display window and take note of the unit of measurement.
  6. c) Measuring Current. Screen fixing cell phones Downtown Miami Brickell.
  7. Turn off power to the circuit.
  8. Cut or unsolder the circuit, creating a place where the meter probes can be inserted.
  9. Select A~ (ac) or A (dc) as desired. Screen fixing cell phones Downtown Miami Brickell.
  10. Plug the black test probe into the COM input jack. Plug the red test probe into the amp or milliamp input jack, depending on the expected value of the reading.
  11. Connect the probe tips to the circuit across the break so that all current will flow through the DMM (a series connection). Screen fixing cell phones Downtown Miami Brickell.
  1. Turn the circuit power back on.

Jumper setting. Screen fixing cell phones Downtown Miami Brickell.

Jumpering means to temporarily complete a circuit or to bypass a break in a circuit

by making a connection from one point to another.

A good conductor wire is used to make a jumper which bypasses the components

and passes on a signal or supply line for further uses. Screen fixing cell phones Downtown Miami Brickell.

When the wire is used as a jumper, it must have some special specifications as required.

These jumper wires can mainly be of two types i.e. insulated and non-insulated. In

the mobile phone, insulated wires are used for jumpers. Screen fixing cell phones Downtown Miami Brickell. The length of a jumper depends on the two points connected in between.

Why do Jumpering? Screen fixing cell phones Downtown Miami Brickell.

While repairing mobile phones, we find that certain faulty components are very difficult to get from the market. To repair such mobile phones, the only immediate option is the use of jumpers. By use of jumpers, we will bypass the faulty components specifically.

How to Jumper

  1. Disassemble mobile phone and place it on a PCB holder. Screen fixing cell phones Downtown Miami Brickell.
  2. Using a multimeter, check track and find the fault or the missing track that need a jumper.
  3. Apply liquid soldering flux to the points where you need to solder jumper wire. Screen fixing cell phones Downtown Miami Brickell.
  4. Cut jumper wire to the desired length and remove its lamination using blade cutter.
  5. Hold one end of the jumper wire and solder it to one point of the faulty circuit track. Use good quality tweezers to hold the wire and good quality of soldering iron and solder wire to solder. Screen fixing cell phones Downtown Miami Brickell.
  6. Now hold the other end of the jumper wire and solder to the other point of the track
  7. Using a multimeter check the jumper.

Mobile Phone Diagnosis.  Screen fixing cell phones Downtown Miami Brickell.

There are two methods that you can use to find out faulty or damaged components in a mobile phone. These are:

  • The cold testing method Screen fixing cell phones Downtown Miami Brickell.
  • The hot testing method

The Cold Testing Method: Cold testing is when we use a multimeter to check the value of resistance at the time of repairing a fault in a mobile phone. During cold testing do not power the phone from any equipment. Screen fixing cell phones Downtown Miami Brickell. Use the diode range and beep sound from the multimeter to find fault in the mobile phone. During cold testing, you should connect the RED probe of the multimeter to the ground of the mobile phone PCB, and use the BLACK probe to touch the testing points of the mobile phone. During the fault-finding and repairing process of each part, component or section.

Hot Testing: The hot testing method is adopted when the fault cannot be found or when the cell phone cannot be repaired using the cold testing method. In this method, the VOLTAGE of the damaged part or component is checked. Screen fixing cell phones Downtown Miami Brickell. The fault is found by powering the mobile phone with a battery which has a DC power supply. Once you power the phone, you should select the DCV (DC Volt) range of the Multimeter. Then you should connect the BLACK probe of the Multimeter to the ground of the phone’s PCB and ensure the RED Probe touches the Testing Points. During hot testing.

What is a fault? Screen fixing cell phones Downtown Miami Brickell.

A fault is a defect (a failure in a circuit) or an electronic device.

What causes faults or failures in mobile phones?

Failures can be caused by any of the following:

  • excess temperature,
  • excess current or voltage,
  • ionizing radiation, Screen fixing cell phones Downtown Miami Brickell.
  • mechanical shock,
  • stress or impact,
  • contamination,
  • mechanical stress,
  • short circuits,
  • imperfect connections, Screen fixing cell phones Downtown Miami Brickell.
  • poor insulation or wiring caused by grounding.

There are three types of mobile phone faults:

(i) Hardware faults occur due to hardware malfunctioning. Screen fixing cell phones Downtown Miami Brickell.

(ii) Software faults occur due to problems with software. Screen fixing cell phones Downtown Miami Brickell.

(iii) Settings faults occur due to wrong/invalid settings. Screen fixing cell phones Downtown Miami Brickell.

Let us discuss each type of faults and how they can be repaired.

Hardware Faults. Screen fixing cell phones Downtown Miami Brickell.

There are many hardware faults that can occur in a mobile phone, but in this section we shall discuss the following:

  1. a) Battery charging faults/problems
  2. b) Mobile phone battery problem (faults)
  3. c) Network not working problem
  4. d) Overheating problem
  5. e) Sound faults
  6. f) Earpiece, ringer and microphone problem
  7. g) Display problems
  8. h) Lighting or LED problem

Battery Charging Faults/Problems Screen fixing cell phones Downtown Miami Brickell.

Battery charging faults manifest in a number of ways:

– The battery is not charged at all,

– There is a sign of battery charging but the battery does not get charged.

– When the charger is inserted, it shows ‘Not Charging’.

– When the charger is connected it shows ‘Bad Connecting Charging’.

– When the charger is inserted the mobile phone gets hot.

Solutions to Battery charging faults. Screen fixing cell phones Downtown Miami Brickell.

  1. Change the charger and check. The voltage must be between 5 and 7 Volts.
  2. Clean, resold or change the charger Connector. Screen fixing cell phones Downtown Miami Brickell.
  3. If the phone shows “FALSE CHARGING” then use a 3.6 Volt Zenor Diode and

do direct charging as show in Figure 32.

  1. If the problem is not solved then change the battery and check again
  2. Check the voltage of the battery connector using a Multimeter. The voltage should be between 1.5 and 3.7 Volts. Screen fixing cell phones Downtown Miami Brickell.
  3. If there is no voltage in the connector check the track of the charging section. Refer to the diagram of the particular model of the mobile phone.
  4. If the problem still persists, check the fuse, coil, and regulator one by one and change the faulty part. Screen fixing cell phones Downtown Miami Brickell.
  5. If the problem is still not solved then heat or change the charging IC.
  6. Finally heat, re-ball or change the Power IC.

Solutions to Battery faults. Screen fixing cell phones Downtown Miami Brickell.

  1. Check the battery connector and charger plug to see if there is any problem.
  2. Check if there is any dust or corrosion in the connector or any broken pin. Clean the points using IPA or cleaning swabs.
  3. Check the Interface Connector to see if there is any dust. If there is dust clean or replace the interface connector. Screen fixing cell phones Downtown Miami Brickell.
  4. If the battery problem is not solved then upgrade the software or operating system to latest version
  5. If the problem is still not solved then check the Mobile Phone PBA current consumption.
  6. Check for any short circuit. Screen fixing cell phones Downtown Miami Brickell.
  7. If there is a serious problem at the board level then it is better to replace the whole Logic Board of the Mobile Cell Phone.
  1. c) Network Not Working Problem. Screen fixing cell phones Downtown Miami Brickell.

The common issues related to this problem include the following:

  • There is no network in the mobile phone
  • There is less or weak network signal
  • Sometimes there is a signal and sometimes there is no network signal.

Solutions to Network fault. Screen fixing cell phones Downtown Miami Brickell.

  1. Manually search for the network. If the ‘no network problem’ persists, then there is a problem with the Antenna Switch. Repair or replace it.
  2. If the network resumes after a manual search but the home network cannot be selected, then there is a problem with the PFO. Repair or change the PFO.
  3. If the Network gets disconnected during phone calls then you should repair or change the Network IC. Screen fixing cell phones Downtown Miami Brickell.
  4. Clean the antenna tips and point.
  5. If the network problem persists, heat or changes the 26MHz Crystal Oscillator.
  6. If the problem is still not solved then heat or change the Antenna Switch. You can also jumper if the Antenna Switch is not available.
  7. Heat, Change or Jumper the PFO if the problem still persists.
  8. Heat, re-ball or change the Network IC.
  9. Heat, re-ball or change the Power IC. Screen fixing cell phones Downtown Miami Brickell.
  10. Heat, re-ball or change the CPU.

Network Signal and Call Drop Problem. Screen fixing cell phones Downtown Miami Brickell.

 If a mobile phone is having network problems and dropping calls, then you should use the following steps to solve it:

  1. Check the SIM Card. Insert the SIM card in other mobile phone and see if the network problem or the ‘call drop’ problem is still there. Screen fixing cell phones Downtown Miami Brickell.
  2. Alternatively, try to insert another SIM card into the mobile phone that has the network problem.
  3. If the problem is caused by the SIM card, then you should change or replace it.
  4. If the problem is still not resolved then upgrade the operating system to the latest version. You can also rewrite the IMEI Number of the mobile cell phone. Screen fixing cell phones Downtown Miami Brickell.
  5. If the problem is not solved then you may have to change the mobile phone

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