SMD component fault finding on PCB

Thread Starter

Musty1988

Joined May 5, 2022
4
Hello friends,
I'm Musty a phone technician, I'm faced with a challenge of identifying faulty SMD component on phones PCB.
* How can I identify a component that is shorting in the circuit?
*How can I use my analog multimeter to identify faulty SMD component such as Capacitor, resistors, diode?
*Many of my Phone PCB are overheating but I can't identify the particular component that is causing the overheating, any trick to this ?

Thank you in anticipation of your kind response.
Musty
 

MisterBill2

Joined Jan 23, 2018
11,914
If a resistor is overheating that can only be from excess current, often caused by excess voltage across the resistor. So unless you are good at tracing the conductor paths on a PCB you need a circuit diagram so that you can understand the source of the fault.
That will be the coast-effective scheme for tracing problems on a circuit board. Otherwise you are going to have to measure the voltage across the capacitors and transistors and discover which voltages are much to low, indicating that the device is passing excess current.
So there is indeed " a trick" and that trick requires being able to read the circuit and observe which parts are in the circuit that should be limiting the current but are not limiting the current. Without this information you are limited just measuring voltages and seeing which ones are not what they should be.
AND, when you locate the failed device, you will need to know what part to replace it with, and because parts in a cell phone are often not marked you will need that information as well.

But if the phones you are trying to repair are not cell phones, it may be simpler, because the parts are not so close to each other.
 

Thread Starter

Musty1988

Joined May 5, 2022
4
I thank you for having time to respond to my request Post. You suggestions and advice is of great help.
But, I will like to gain more knowledge on how to measure the PCB voltage and test on identify faulty SMD component on circuit. Once more, I say thank you .
 

MisterBill2

Joined Jan 23, 2018
11,914
The way to identify a faulty component would be to measure the voltage across that component and compare that measurement with what the voltage is supposed to be with correct operation of the circuit.
Knowing what the circuit is and how it is supposed to be performing will be very valuable in not needing to check every component. Also, on many instances, the failure of one component will also affect the voltage of other components.
For the most efficient methods of determining which parts have failed you do need not only the circuit diagram and understanding of how it functions, but also you need to know what the symptom or complaint is. Skill in replacing components is seldom enough to be a successful service person. Certainly that skill is needed but it is not all that is needed.
 

Thread Starter

Musty1988

Joined May 5, 2022
4
The way to identify a faulty component would be to measure the voltage across that component and compare that measurement with what the voltage is supposed to be with correct operation of the circuit.
Knowing what the circuit is and how it is supposed to be performing will be very valuable in not needing to check every component. Also, on many instances, the failure of one component will also affect the voltage of other components.
For the most efficient methods of determining which parts have failed you do need not only the circuit diagram and understanding of how it functions, but also you need to know what the symptom or complaint is. Skill in replacing components is seldom enough to be a successful service person. Certainly that skill is needed but it is not all that is needed.
Thank you so much for your kind and useful advice/solutions.
 
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