How to Check Keypad of a Mobile Phone
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.
How to Check Ringer of a Mobile Phone
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.
How to Check Speaker or Earpiece of a Mobile Phone
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.
How to Check Microphone or Mic of a Mobile Phone
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.
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.
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.
How to Check Vibrator or Motor of a Mobile Phone
To check vibrator or motor of a mobile phone, 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.
How to Check Electronic Components
Coil
Check the SMD coil 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 SMD resistor is faulty. Replace it with a new one.
Capacitor
To check SMD Capacitor 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.
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.