how to check mobile phone faults and defects with a multimeter

Mobile phones are useful for our day to day activities as we already now how important it is to keep intouch with family incase of emergency, and communicating with people and connected to promote our business. 

Our mobile phones and gadget as an electronic are vary fragile when it comes to handling them,  while some of us uses leather jacket and some silicone and as well as rubber pouch e.t.c all to protect our devices from getting damaged most especially the stylish and PDA designed devices with fragile capacitance and resistance touch digitizer. 

Now what do we need to get our devices diagnosed properly when faulty so as to know the syptoms and solutions to these some of which are : 

Multimeter, Oscilloscope, Screwdrivers Dc power supply and others.

But today we would be talking about multimeter

Firstly what do we understand by multimeter 

Multimeter is an electronic measuring device or instrument used in the combination of several measurement function in one unit, a multimeter measures voltage, current, resistance and so on..

We have digital wchich you already know how it looks and analog multimeter which uses a pointer to show readings.

Today i will be talking about Digital multimeter and what it can measure

 Multimeter

A digital multimeter according to wikipedia could be used in measuring two or more electrical values principally voltage (volts), current (amps) and resistance (ohms). ... Digital multimeters combine the testing capabilities of single-task meters—the voltmeter (for measuring volts), ammeter (amps) and ohmmeter (ohms).

Now how do we check phone components with a digital multimeter

Ringer: To check if the ringer of a mobile phone is faulty or damaged,

keep the multimeter in buzzer mode and check the ringer. Value must be between 8 to 10 Ohms. If the value is between this range then the ringer is good and does not need replacement. If the value on multimeter is 4-5 or 12-14 then change the ringer.

Vibrator or Motor: Keep the multimeter in Buzzer Mode and check the vibrator, Value must be 8 to 16 Ohms. If the value is between 8-16 Ohms then the vibrator is good. Otherwise change it.

Speaker or Earpiece: Check the speaker / earpiece with a multimeter on Buzzer mode. Value must be in the range of 25 to 35 Ohms. If the value is in this range then the speaker / earpiece is OK and need not be changed. Otherwise, change the speaker / earpiece.

Microphone or Mic: Keep the multimeter in buzzer mode and check the microphone. Value reading on the multimeter must be in the range of 600 to 1800 Ohms. There will also be a Beep or Buzz sound from the multimeter. NOTE:  Please note that only one side of the microphone will show value. If we check by reversing the Red and Black Probes / Test Leads of the multimeter and check the microphone then there will be no value.

Coil: Check it with a multimeter on Buzzer Mode. If it is good then it the multimeter will give a Beep or Buzz sound. If there is no sound then the coil is faulty. Replace it with a new one.

Resistor or Resistance: Check it with a multimeter on Buzzer Mode. If it is good then the multimeter will give a Beep or Buzz sound. If there is no sound then the resistor is faulty. Replace it with a new one.

Capacitor: Check it with a multimeter on Buzzer Mode. If it is good then the multimeter will NOT give any Beep or Buzz sound. If there is sound then the capacitor is faulty. Replace it with a new one.

Diode: Check it with a multimeter on Buzzer Mode. If it is good then the multimeter will NOT give any Beep or Buzz sound. If there is sound then the diode is faulty. Replace it with a new one.

LED: Keep the multimeter in Buzzer mode and check the LED. If the LED is good then they will glow otherwise not.

Coil and Boosting Coil: Check for continuity. If there is continuity then the coil or the Boost Coil is good otherwise it is faulty.

Keypad: Keep the multimeter on Buzzer mode and check Rows and Columns or the Key Pad. If there is Beep or Buzz sound from the multimeter then Keypad is ok, otherwise it is faulty.

Battery Connector: Keep multimeter on 20V DC and check. Value must be 1.5 to 3.5 V DC.

Battery: Check voltage with a multimeter. Keep multimeter on 20V DC and check. Value must be 3.7 V DC or above.

ON / OFF Switch: Check voltage with a multimeter. Keep multimeter on 20V DC and check. Value must be between 2.5 to 3.7 V DC.

Network IC: Use a Analog DC Power Supply to check Network IC. Switch ON DC Power Supply and call any number from your mobile phone. The Needle of the DC Ampere will start moving. This shows that the Network IC is OK and not fault.

Power IC and CPU: Adjust voltage of the DC Power Supply to 4.2. Place the Red Probe / Test Lead of the DC Power Power Supply to the “+” of the Battery Connector of the mobile phone and the Black Probe / Test Lead to “-“. If DC Ampere is over 6 then Power IC or CPU is damaged. Check by replacing Power IC and the CPU one by one.

If there is no movement of the Ampere Needle of the Power Supply then the Battery connector, On / OFF Switch Track, RTC or Network Crystal is damaged. Give heat to these components using hot air blower. If the problem is not solved then check by replacing them one by one.

If the Ampere Needle fluctuates below 2 ten there could be problem with software or RTC (Real Time Clock).

If the Ampere needle stands at some fixed point then there is problem with the Flash IC.

If there is beep sound from the DC Power Supply then there is problem with “+” and “-” or the mobile handset is short.

PS: When checking a faulty mobile phone with DC Power supply, connect the Red Probe to “+” and Black Probe to “-” of the Battery Connector of the Mobile Phone.