The first thing you have to check in dead mobile phones after checking the battery is shorting. And if it is short, you will first have to remove it to get it repaired. All technicians should know how to remove a short circuit in cell phones.
Reasons for shorting in mobile phones:
- Phone falling in water. This is the most common reason
- Handset overheating.
- Using an incompatible or faulty charger for charging
- Sometimes, sparks or smoke coming out of the handset due to any reason.
We have to understand the below 2 terms of electronics to understand shorting better:
- Open circuit: If a track is broken, then it is said that the track is open.
- Short circuit: If 2 parallel separate tracks touch each other due to some fault, it is called short circuit.
Note: In circuit boards of cell phones, tablets or any other electronic device, there are tracks instead of wires through which current flows. Hence we use the term ‘tracks’ instead of wires or cables.
How to check shorting in mobile phones with multimeter:
We can easily check whether there is shorting in the circuit board or not with the help of a multimeter. Follow the steps below:
- Keep the multimeter on continuity setting (Also called diode setting)
- Identify the positive and negative terminals of the battery connector. The positive terminal (+) is the pin of the battery connector where the positive terminal of the battery touches on it. It is also called vBat (Battery Voltage) pin. While negative terminal (-) is the pin of the battery connector where the negative terminal of the battery touches on it. It is also called GND (Ground) pin.
- Now touch the red probe (+) of the multimeter to negative terminal of the battery connector.
If you see any reading on the multimeter or hear a continuous beep sound, then the motherboard is short i.e your mobile phone is short. And if there is no reading or no continuous beep sound, the board is not short. If you are using an analogue multimeter, keep it on Ohms(x10) setting. If the pointer (needle) moves even a little, than it is short, otherwise, it’s okay.
How to check shorting in mobile phones with DC Power Supply:
A DC Supply is also called jhatka machine or battery eliminator. Its work is to convert AC voltage coming from an AC volt source to DC voltage. To check shorting, follow the step below:
- Switch on the DC power supply. Now select the output voltage as much as its battery voltage. You can read it on the battery. In most phones, it is 3.7v or 3.8v. Some Chinese phones have output of 4.2 volt.
- Connect red probe to the positive terminal of the battery connector (vBat pin) and the black probe to the negative terminal (GND)as well as the 3rd pin called BSI. And do not touch any other key or button.
Now, if you see any amount of current on the screen, then it means, the circuit board is short.
And if, there is the screen shows ‘0.00’ in the current reading, then it is okay.
Problems in handset if it is short:
- Battery drains and discharges fast
- Switches off automatically or restarts.
If the circuit board is short, you will first have to remove shorting for fixing the problem, especially, if the handset is in dead condition. Learn how to remove shorting in mobile phones.
Note: The above procedure to check shorting is the same for all brands of cell phones and tablets including Samsung, iPhone, Nokia, Sony, HTC, Motorola and Chinese handsets. It will be the same for all smartphones be it based on iOS, android or Windows OS.
Please let us know your results in the comments section below.