How To Use DC Power Supply | MobileRepairingOnline

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How To Use DC Power Supply

31 Oct 2018
hi, today I'd like to answer a very common question I get from beginner mobile device technician to my mobile phone repair class which is a, how do I use a DC power supply to power a cell phone? why would I want to use a DC power supply to check and find the faults in feature phone and smartphones?
DC Power Supply guide for mobile phones repairing
fault tracing principles

let's start with the why there are two answers for the Y the first answer to why I would use a DC power supply to power where the cell phones are that this R.s 300 mini power supply
Cheap converter dc to dc Adjustable Step Down Module power supply
mini nonadjustable 

that you would buy on mobile malls here in Asia it's pretty flimsy they died fairly often and especially if you're doing what we do which is plugging them into liquid damage mobile devices or Android and Mac devices that have short circuits you're bound to go through a lot of these and it gets tiring after a while to continuously spend R.s 300 on something that breaks. 

The second as to the why is that by using a DC power supply I can intuitively tell exactly how much power the smartphone is using so for example:
find principles here to test smartphones with digital power supply
cable connecting examples

I've hooked up a DC power supply connector to this the smartphone that I have down here and as you can see at 3.8 volts I can see that this phone is pulling 200 amps and as you can see in a picture 

Ampere on working cell phone repairing examples theoretical and practical limits of dynamic voltage scaling
practical knowledge

the amount of Amperes a phone is using can very often be as a link to the type of problem it's having the same way that a doctor is going to tell if you have a niche over here you may have this illness if you have this temperature with your fever you may have this illness that's the same thing here oh if this IC integrated circuit is bad if the phone may be drawing this many amps if that integrated circuit is bad the device may be drawing that many amps it's a way to kind of try and narrow down what's wrong once I realize that there's a pattern every time this IC is blown the phone is drawing this many amps I don't have to go through and repeat that same troubleshooting process every single time I can just go huh the last five times it was drawing 58 amps IC a was corroded so when I see it's drawing 58 a mess rather than spend 30 minutes troubleshooting I can check integrated circuit a within the first minute and bam I have a solution to my customer phone problem. 
if you have Digital DC Power Supply already that's good or if not! visit this link to Review Best Top DC Power Supply and find one which suits for your price range
Here are some examples of substituting DC Power Supply Ampere on working mobile phones repair tracing faults
digital dc power supply
If you are a new mobile technician and don't know what is this digital dc power supply? first, read this article on Wikipedia for a better understanding of AC-to-DC supply. 
A regulated DC power supply is converted unregulated AC Alternating Current into a constant DC stable voltage
dc power supply description

if you are an electronics student and reading this information to know more about the basics of DC power supplies, PSU, detailing linear and switching types and their advantages and disadvantages read this article also

Now the next question is going to be how do I connect this how do I connect a smartphone to a variable DC power supply?

so here we have the smartphone so on this end this is a plus and minus wires we need to plug into the smartphone. so you're gonna have a black wire which is going to be ground so this here is your red wire this is your positive of your DC power supply
The intended use of these plugs is on the cable connected to a power supply
dc power supply crocodile cable

as you can see in the picture I've already got two wired up here so in order to be compatible with all the different android devices I would suggest you get set up your DC power supply voltage on 4.1 to 4.2 volt and 200 Ampere because android phone or android tablet device often is not going to turn on if you do not plug them into a 4.1 DC Volt on your switching power supply.
Suitable for multimeter, power supply and other electronic equipment
connecting cables to phone
so that is how you would use a DC power supply to power a smartphone you just plug it into these two wires to the Digital DC power supply it has functionality that allows you to watch your customer's phone Ampere and voltage readings 

Here are some examples of voltage and Ampere on working phone repairing
voltage and ampere readings

now you can also use this method here to power up a feature phone so you have to buy these little cables
Buy DC Power Supply Testing Cable Repair Tool Dedicated Wire to read Mobile Phone circuit
Mobile Phone Current Test Cable with USB Output
these cables allow you to plug feature phones into a best DC power supply with their battery connectors so this is a nice little cable over here it's nicely sleeved it reports proper temperature information supposedly you never know stuff from China and I can show you what that looks like in this picture
Mobile phone repair tool DC Power Supply Cable with USB Output to Test voltage and ampere
measure USB current with dc power supply


see over here it's got connectors that will attach to the battery connector of a feature phone as you can see in the picture below 
How to connect Testing Cables to DC Power Supply
Wire to read Mobile Phone circuit
you can power the feature phone using a DC power supply with those cables you would just take them and you plug the red end into the red part of your DC power supply the black end ins the black part of your DC power supply connector you would set the voltage to the feature phone battery voltage around three point seven three-point eight volts and then you would plug this end into the battery connector on the feature phone and then you would be able to power the old mobile phones using the DC power supply rather than having and go around your shop and try to find your customer old mobile phone battery that you know works and you'd also be able to see the amount of amperage that it's drawing directly on the digital power supply which is pretty cool obviously try to avoid making the mistake of plugging in your feature Phone using smartphone voltage won't exactly be a happy feature phone Set DC power supply voltage on 3.7 and Ampere on 150 to check feature phone.

DC Power Supply for Mobile Repairing Price

in this article, I am also sharing the information with you about the best dc power supplies rate because the reader also went to know where to buy their dc power supply.
the website is listed below
Amazon
Aliexpress
Alibaba
eBay

the reason I bring this up is that I would say a good 99% of the people reading this post went to know the price before buying the best dc power supply
remember, if you're just gonna want to go for the cheaper power supply don't go for something that's way too cheap because those are gonna send ripple currents and voltages and do all sorts of nasty stuff now you can also use this. 


if you are interested in to read a PDF Book on regulated dc power supply click here

How to Find Mobile PCB Fault using DC Power Supply

you can also use DC power supply to supply DC (Direct Current) to a mobile phone PCB Printed Circuit Board. most mobile repair technicians used DC power supply to switch ON a smartphone without their batteries. the Supply can be used to substitute for the Cell Phone GND, +VBAT Battery Voltage when doing hot testing on the Mobile PCB. this is being used to trace the +VBAT, VCC main line in Mobile Phone PCB. the Supply provides high stability output voltage and its constant ampere can auto-conversion. you can use power supply in many different areas of the mobile phone PCB for hot testing.

To learn hot testing on mobile phone circuit follows these steps:

step one: adjust power supply on 3.8volt then connect its wires to mobile battery connectors

step two: turn ON the mobile phone

step three: now place multimeter black probe on mobile phone PCB Ground and place red probe on the print of VBB to check the DC voltage on phone circuit.
adjust dc power supply on four volts then connect its wires to mobile circuit
black on Ground and on VBB
To know the testing principle for mobile phone repairing read Digital Multimeter step by step guide

What is the Uses of DC Power Supply in Mobile Phone Repairing?

You can use DC power supply to check four things in your customer phone
  1. customer phone is dead or not
  2. customer phone circuit is a short circuit or not
  3. customer phone circuit prints are open or not
  4. customer phone has a software problem
1. Customer Phone is Dead or Not
how to connect mobile phone with DC Power Supply
connecting examples

Set DC power supply Voltage on 3.7 and Ampere on 150 to check feature phone.

Set DC power supply Voltage on 4.1 and Ampere on 200 to check smartphone.

If you are connecting Tablet then set switch supply Voltage on 4.2 and Ampere on 200.

Now switch ON the phone and see Ampere Reading. 

how to read Ampere Reading on DC Power Supply
DC Power Supply feature phone Ampere

Note: If the Ampere does not show any reading it means your phone power input track on battery connector is open.

2. Customer Phone Circuit is a Short Circuit or Not 


Reasons for short circuit in mobile phone circuit :


1, Phone falling into toilet water or liquid damage. this is the most common reason that mobile phone users are facing in routine life.

2, The smartphone is warming again and again.

3, Using an incompatible or faulty phone charger for charging the battery. and also when you use the wrong charger to charge your phone and phone get hot.

4, Sometimes due to any reason phone has fallen down or crashed.

To check the mobile phone short circuit with dc power supply follow the step below: 

step one: Set DC power supply output voltage on 3.7v or 4.1 volts.

step two: Connect the red wire to the positive terminal of the battery connector (+VBAT pin) and the black wire to the negative terminal (GND)as well as the 3rd pin called BSI battery status interface.

DC Power Supply Reading
half shorting reading look like this on the digital power supply
half short circuit
Reading one: Now, if you see any amount of ampere on the screen, without you press phone power button then it means, the mobile phone is a short circuit.

Half Short Circuit

Reading twoAnd if there is the screen shows ‘0.38’ to ‘0.58’ in the ampere reading, then it is Half short circuit.

Full Short Circuit

Reading threeif you see on the screen shows ‘0.00’ in the voltage and ampere reading, then the mobile phone circuit is the full short circuit

3. Customer Phone Circuit Prints are Open or Not

To understand mobile phone short circuit better in your customer smartphone you have to know 2 terms of electronics:

Phone Circuit Print is Open: if a mobile phone print is broken, then it is said that the Print is open.
mobile phone circuit is open due to short circuit on between prints
cell phone circuit track is open


Phone Circuit Prints are Short circuit: if 2 parallel separate Prints positive and negative touch each other due to fault in the mobile phone PCB, it is called a short circuit.
mobile phone circuit tracks are short circuit due to fallen damage
component goes short

Note: In PCB boards of the mobile phone, smartphone and tablets there is the print instead of copper wires through which dc current flows. Hence we use the term ‘Prints’ instead of copper wires or cables.


Now let me tell you the Problems of the short circuit in smartphones:

1, When you switch ON the phone, it goes switch OFF automatically after a few minutes.
2, Phone goes completely dead.
3, Phone battery goes drains and discharges fast.
4, The phone goes hot and the get Hang.

Note: The above procedure to check short circuit in the mobile phone with DC Power Supply is the same for all Mobile brands and tablets including Microsoft phone, Samsung, Nokia, Apple iPhone, Sony Xperia, HTC, Motorola, Q mobile Vivo, and Oppo handsets. It will be the same for all iOS, Android or Windows OS smartphones.

4. Customer Phone has a Software Problem 

Set DC power supply output voltage on 3.7volt on the feature phone and 4.1 volts on the smartphone. 

Connect red wire of the DC power supply connector cable to the positive terminal of the battery connector and black wire to the negative terminal and yellow probe to the middle pin of the battery connector of the feature phone. 

In smartphone connect the power supply cable red wire to the positive terminal of the handset battery connector +VBAT and the black wire to the negative GND as well as the 3rd pin BSI to check the phone.

Now switch ON the phone and see Ampere reading. if you see 003 or 005 amperes on the screen, when you press the phone power button then it means, the feature phone software is corrupt.

And in the smartphone, you see at ampere reading screen 010 or 015 when you press the power button of the phone if the phone is in software fault.
Ampere Reading Shows 010 or 014 in software fault
Ampere Reading Examples

Remember, in many cases of software fault in a smartphone. the smartphone switch on but the screen show startup logo and digital dc power supply reading switch between 010 to 020 ampere

These are the examples readings of digital DC Power Supply for repairing mobile phones faults. so that is it for today post that is how you can use a DC power supply to power a smartphone and feature phone both to put the voltage and Ampere on your DC power supply screen and free information that's why I do it and as always I hope did you learn something

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