DC Power Supply is a must having tool for Mobile repairing. It is used for finding various types of Faults in Mobile phones. Let us discuss how to find faults using DC Power Supply.

DC Power Supply basically has a Voltmeter, an Ammeter, and two Probes.

DC Power Supply
DC Power Supply

We can adjust the voltage ranging from 0V to 15V using a Voltage regulator. Some Power supply comes with 0V to 30V, 0V to 60V also. The voltmeter measures the input voltage given to the mobile.

Similarly, we can limit the Amperage of DC Power Supply. DC Power Supply comes with up to 10A limit. We can regulate the amperage of DC Power supply using Ampere Regulator.

The ammeter measures the current consumption by the mobile. It ranges from 0mA to 1000mA. The unit of current is 1 Ampere (1A).

1A= 1000mA

I have listed down the best uses of DC Power Supply.

  • To power on mobile phone without battery
  • To boost up battery voltage
  • To find out Shorting in mobile phones
  • To check Stuck on logo and Boot looping in Mobile Phones
  • To check some parts in the Mobile Phones

Let’s discuss one by one.

To Power on Mobile Phone without Battery

The first step to check a dead mobile is to check the battery. Sometimes Mobile is ok, but there is a problem with the battery. You can use DC Power Supply to check whether the mobile switches on by using connecting the Probes to the Battery Connectors.

DC Power Supply Probes

There are two Probes in a DC Power Supply.

  • Positive Probe or Red Probe
  • Negative or Ground Probe or Black Probe.

To power on the mobile phone :

  1. Switch on the DC Power Supply.
  2. Set the voltage in between 3.7V to 4.2V
  3. Connect the Red Probe with the positive pin of the battery connector and Black probe to the Ground.

For an in-built battery, we can use dedicated power cable instead of common probes.

dedicated power cable
Dedicated power cable

To boost up the Battery voltage

When a mobile or smartphone is dead or switched off for a long time, the battery voltage reduces gradually.

The normal voltage of the battery is between 3.7V to 4.2V. When the battery voltage goes below 2.8V, it can not be charged with a normal charger. In this case, we need to boost up the battery voltage with the help of DC Power Supply.

Sometimes the battery voltage reduces to 0V due to full-shorting in the mobile. A normal charger can not boost up the voltage of the battery.

How to boost up the battery voltage

  • Set DC Power Supply voltage at 4.2V and Amperage 2A.
  • Connect the Red Probe or Positive Probe to Positive(+) terminal of the battery and Black probe or Negative Probe to Negative(-) terminal of the battery.
  • Keep charging for 2 to 5 minutes and disconnect the probes.
  • Check the battery voltage.
  • When Battery voltage goes beyond 3V, do charging using a normal charger to reach VBatt to 3.8V.
  • You can boost the Battery voltage to 3.8V using DC Power Supply also. But it is always recommended to charge with the normal charger when the battery voltage reaches to the threshold voltage(2.8V)

To find out the Shorting in Mobile Phones

We can find out the shorting in mobile phones using the DC Power Supply easily. Shorting happens when the positive line in the Mobile phone comes in contact with the ground due to the faulty components or ICs.

How to check Shorting

  • Set the DC Power Supply at 4V and 1.5A.
  • Connect the positive probe of DC Power Supply to Positive Battery connector and -ve probe of DC Power Supply to Negative Battery Connector.
  • Check the Current consumption at DC Power Supply without pressing the Power key of the Mobile Phone. You can get 3 types of Current readings.
  1. Current Reading = Set Current
  2. Current Reading < Set Current
  3. Current Reading = 0 mA

Current Reading = Set Current

If Current consumption is equal to set current without pressing the power button, this condition is known as Full Shorting.

Some components like Capacitors, Diodes are fully shorted to ground. The internal resistance is 0 ohm of shorted component.

You can identify the shorted component by using Thermal Camera or Isopropyl Alcohol. Because the shorted component releases heat when the power supply is connected to Mobile Motherboard.

Current Reading < Set Current

If the current consumption is less than set current (in this case, 1.5A) without pressing the power key, it is called Half-Shorting. The half-shorted component in Mobile Phone is partially shorted. 

Some mobile phones switch on in the case of half shorting. But it causes overheating of the Mobile phone. Also some functions do not work perfectly due to half shorting.

Current Reading = 0 mA

If the current reading is equal to 0 mA, that means there is no drop in the current before pressing the Power Switch, then the mobile is in OK condition. There is no shorting in this condition.

To check Stuck on logo and Boot looping in Mobile Phones

When you switch on the smartphone or mobile and it is unable to boot completely and stuck on company’s logo, this condition is popularly known as ‘Stuck on logo

When the smartphone restarts continuously, this condition is known as ‘Boot looping

Both Stuck on logo and Boot looping occur when there is software as well as hardware problem. Before proceeding any software work in mobile, check for hardware problem.

A weak and faulty battery can cause your smartphone to stuck on logo or Boot looping. So a DC power supply can help you to find out the battery problem causing Stuck on logo and Boot looping.

The following video helps you to learn how a faulty battery can boot loop the mobile.

Subscribe to the channel

To check some parts in the Mobile Phones

DC power supply is very useful to check some parts of the smartphones.

The parts like Vibrator, Ear speaker, Ringer, Camera Flashlight, etc can be checked by DC power supply.

How to check Vibrator using dc power supply

Vibrator is a small part of the smartphone. It is usually a motor which creates vibration.

Mobile Vibrator

To test the vibrator:

  1. Set dc power supply voltage at 3V
  2. Connect both probes of dc power supply to the terminals of the vibrator, irrespective of polarity.
  3. If the motor spins and vibrates, then it is ok.

How to check Ear speaker and Ringer using dc power supply

Mobile Ear Speaker

To test ear speaker and ringer:

  1. Set dc power supply voltage at 1.8V
  2. Connect one of the probes of dc power supply to one of the terminals of the ear speaker / ringer and touch another probe to the remaining terminal.
  3. You will hear some speaker noise while touching. In this case, ear speaker/ringer is ok.

These are some basic uses of dc power supply in mobile repairing. I hope this article must help you to develop your mobile repairing skill.

If there are any queries regarding dc power supply, please comment below.


  1. Thank you very much for this piece,yet I want to ask, when the current reads as set current on the second (i.e1.5A) and one needs to locate the circuit that is partially shorten,do we still use isopropyl alcohol to do so,and would it still go hot as the first read set current?


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