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

 Cell Phone Diagnosis

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
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. 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 component prints. During the fault-finding and repairing process of each part, component or section, you should receive the following correct values:

Ear Phone Connector Tip (+ , -): 500 to 700

Loud Speaker / Ringer Connector Tip (+,-): 300 to 600

Battery Connector Tip (+): 300 to 500

Battery Connector Tip (Sense): above 800

Display Connector Supply Pins: 250 to 400

Display Connector Signal Pins: 500 to 800

Camera Connector Supply Pins: 250 to 400

Camera Connector Signal Pins: 600 to 900

Key Tip (Row and Column): 400 to 800

Charger Connector Tip: 600 to 700

Vibrator Motor Connector: 40 to 500

Power ON / OFF Switch Point (+): 600 to 900

MIC Connector Tip (Analog MIC) (+,-): 700 to 900

Battery Charging Out Point (+,-): 300 to 400

SIM Card Connector Pin 1 (VSim): 500 to 700

SIM Card Connector Pin 2,3,6: 400 to 800

SIM Card Connector Pin 4 (GND): 00 (Beep)

Micro SD Card Connector Pin 4: 500 to 600

Micro Card Connector Pin 6 (GND): 00 (Beep)

Micro Card Connector Pin 1,2,3,5,7,8: 600 to 800

RTC: 400 to 500

Data RX and TX Pins: 600 to 700

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. 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, the voltage of different part or sections should be as follows (all values in Volt):

Ear Phone Connector Tip (+ , -) when working: 0 to 2.5

Loud Speaker / Ringer Connector Tip (+,-) when working: 0 to 2.5

Battery Connector Tip (+): 3.7

Display Connector Supply Pins: 1.8 to 2.9

Display Connector Signal Pins when working: 0 to 1.8

Camera Connector Supply Pins: 1.8 to 2.9

Camera Connector Signal Pins when working: 0 to 1.8

Key Tip (Row and Column) One Side: 1.8 to 2.8

Charger Connector Tip: 5 to 6

Vibrator Motor Connector Tip when Working: 1.9 to 3.6

Power ON / OFF Switch Point (+): 3 to 3.6

MIC Connector Tip (Analog MIC) (+,-): 1.8 to 3.0

Battery Charging Out Point (+,-): 3.7 to 4.2

SIM Card Connector Pin 1 (VSim) when SIM Connected: 1.8 to 3.0

SIM Card Connector Pin 2,3,6 when working: 0 to 2.8

Micro SD Card Connector Pin: 2.8

Micro Card Connector Pin 1,2,3,5,7,8: 0 to 2.8

Data RX and TX Pins: 1.8 to 2.8

You now know how to diagnose a fault in a mobile phone using the hot and cold testing method.

 

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