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DC Power Supply uses and functions in Mobile Repair

dc power supply
60V-10A DC Power Supply

If you are running a Mobile Repair Shop, you should know DC Power Supply uses to find faults.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 use the dc power supply in mobile repair.

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

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

Similarly, we can limit the Amperage of the 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 a mobile phone without a battery
  • To boost up the battery voltage
  • To find out Shorting in mobile phones
  • To check Stuck on the logo and Boot looping in Mobile Phones
  • To check some parts in the Mobile Phones

Let’s discuss them 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
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 between 3.7V to 4.2V
  3. Connect the Red Probe with the positive pin of the battery connector and the Black probe to the Ground.

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

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 cannot be charged with a normal charger. In this case, we need to boost up the battery voltage with the help of a DC Power Supply.

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

How to boost up the battery voltage

  1. Set DC Power Supply voltage at 4.2V and Amperage 2A.
  2. Connect the Red Probe or Positive Probe to the Positive (+) terminal of the battery and the Black probe or Negative Probe to the Negative (-) terminal of the battery.
  3. Keep charging for 2 to 5 minutes and disconnect the probes.
  4. Check the battery voltage.
  5. When the Battery voltage goes beyond 3V, do charging using a normal charger to reach VBatt to 3.8V.
  6. 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 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 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 the Positive Battery connector and -ve probe of DC Power Supply to the 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.
  • Current Reading = Set Current
  • Current Reading < Set Current
  • Current Reading = 0 mA

Current Reading = Set Current

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

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

You can identify the shorted component by using a 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 the 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 the logo and Boot looping in Mobile Phones

When you switch on the smartphone or mobile and it is unable to boot completely and is stuck on the 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 the logo and Boot looping occur when there is a software as well as a hardware problem. Before proceeding with any software work on mobile, check for hardware problems.

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

To check some parts in the Mobile Phones

DC power supply is very useful to check some parts of 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

A vibrator is a small part of the smartphone. It is usually a motor that creates vibration.

mobile vibrator
Mobile Phone Vibrator

To test the vibrator:

  1. Set dc power supply voltage at 3V
  2. Connect both probes of the 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

To test the ear speaker and ringer:

Mobile ear speaker
Mobile ear speaker
  1. Set dc power supply voltage at 1.8V
  2. Connect one of the probes of the 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 the dc power supply, please comment below.

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Hi, My name is Rajesh Behera. I am the founder of RepairTheMobile. I am a Mechanical Engineer and currently working in an MNC. Mobile phone repair is my passion. There are a lot of mobile phone repair videos available on YouTube. But most of these videos are not properly explained due to the lack of proper knowledge of the technicians. Due to the demand for mobile phones, lots of new mobile technicians are opening their repair shops. They are only doing basic works like combo (display screen) replacement, charging port change, battery replacement, etc. They don’t know the proper way of finding faults like dead phone repair, backlight & graphics issues, network problems etc. They cannot close their shops to get offline training. So, I decided to make RepairTheMobile to help new mobile technicians. RepairTheMobile is absolutely free learning platform. It offers FREE mobile repair training from basic level to advanced level. Keep learning & keep earning.


  1. Dear Rajesh, I’m impressed with your YT videos. I’m having problem old S7 edge. I’m really impressed with your solution. The real problem is I can’t repair it myself as I don’t have the tools you shown. I live in Bangalore. Please suggest someone here in Bangalore who understand your video and can do it.


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