In cellphone repair its important to be able to identify elect I'mric components on cellphone PCB. It helps you easily troubleshoot faulty components. Below are the lists of electronic components you will find on cellphone PCBs.
1. Capacitors.
It is use for storing current in form of electric charge on its plates. it consists of two metal plates separated by a dielectric material. most capacitors you will find on cellphone boards are surface mounted, meaning that they are extremely small in size. They are usually brown in color. Polarized capacitors are usually marked on one edge with a yellow color strip to indicated its negative.
Types of capacitors found on cellphones.
2. Resistors
The symbol of a Resistor, as you can see that it is being label started with letter ''R''meaning for Resistance and followed by a ''Mounted Code'', that code is the number of that resistor for easy identification and search reason on the whole structure of a PCB board. Then, also ob-course the Resistance Value for test and check up procedures, like for example ''R4400 = 47K'' it means that Resistor number 4400 connected on that particular circuit's value is 47K or 47000 ohms. In that way we can easily trace and and test that component using a Multi-meter tester.
There are two types shown in here, The first one is Fixed Resistor and the other one with a line across to it is called Thermistor or Thermal Resistor.
Thermistor or Thermal resistor is a variable Resistor, meaning it's resistance value is changeable. Thermal defines to heat temperature, it is being change by a current or voltage flowing across to it. It also have a capability to shut off when a voltage or current drive it to a maximum temperature level.
While the Fixed Resistor, remains steady to it's resistance value.
3. EMI filter
EMI-Electromagnetic Interference or ESD-Electrostatic Discharge is pack in tiny chips called by many technician as Crystal IC for it glows like a crystal glass.
EMI-ESD filter are used to protect a certain circuit from hazardous Electromagnetic Interference and Electrostatic Discharge.
Electromagnetic Interference cause by elecromagnetic machines like like a chainsaw, an electric blower and other things that has high frequency levels.
Electrostatic Discharge (ESD)- a human body is a potential source of electrostatic and can cause damage, especially to semiconductor devices when touching it.
EMI-ESD Filters can be easily breakdown and busted when those two elements occurs. It often used in Keypads circuit, Display circuit, USB (Universal Serial Bus)Interface circuit, Removable Flash Memory Devices circuit and other Interface that is prone to ESD and EMI hazards.
4. Transistors
There are two types of standard transistors, NPN and PNP, with different circuit symbols. The letters refer to the layers of semiconductor material used to make the transistor. Most transistors used today are NPN because this is the easiest type to make from silicon.
A transistor is a semiconductor device used to amplify and switch electronic signals.
The transistor is the fundamental building block of modern electronic devices, and its presence is ubiquitous in modern electronic systems.
It is labeled with letter ''V'' and then the mounting code and product code.
The leads are labeled base (B), collector (C) and emitter (E) in some schematics while in cellphone schematics is not, just be familiar with each leads.
What is a MOSFET?
Simple brief explanation, In mobile phones its is being used as a Switching circuit to the Camera Flash interface. It holds the large amount of voltage and then feed to camera flash light when it is being click to take a picture. That is why the Flash of the camera give a more bright light and speed in just a matter of blink of an naked eye..
The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a device used for amplifying or switching electronic signals.
A Power MOSFET is a specific type of metal oxide semiconductor field-effect transistor (MOSFET) designed to handle large amounts of power.
Its main advantages are high commutation speed and good efficiency at low voltages.
The power MOSFET is the most widely used low-voltage (i.e. less than 200 V) switch. It can be found in most power supplies, DC to DC converters and low voltage controller circuits.
There are many types Field effect transistor, this is the one is commonly used in mobile phone circuit.
5.Fuse
A fuse is the component used to protect from sudden arise of the desired amount of currents and voltages into a certain circuit. The fuse will be blown out if a certain circuit have a very low resistance or shorted. a Fuseo is made by a metal wire that can be easily busted if a high current or voltage will flow on it.
It is labeled letter "F" means a fusible device then a product code or number.
A fuse is often used in a charging circuit of any mobile phones. The phone will indicate no charging reaction if a fuse is already blown.
6.Coils.
The symbol of a coil (inductor) is just like a wave lines which emphasized that there is a winding component on that circuit which means that the coil is connected in there. In cellphone circuit many coil is being used in B+ voltage filtering to avoid saturated voltage and current.
coils are easy to identify in an schematic diagram for they are form into a wave line. It is labeled with letter "L" which means Inductance.
In cellphone circuit coils are also prone to be easily damaged like when it is being used in B+ line filtering. It will be blown out or end up busted if some short circuit occurs.
7.Clock crystal oscilatior.
An electronic component circuit that have the ability create real time clock signal. a vibrating crystal that made by so-called piezoelectric material produce a maintained and sustained frequency such as applied into real time clock like quartz wristwatches.. This one is being used to maintain the clock system in a digital circuit and maintain Radio Frequency transmitters and Receivers.
It labeled sleep clock oscillator or just clock oscillator in schematic diagrams.
In Cellphones if the clock oscillator is faulty it results on not powering the phone. The phone is dead, because as stated above that oscillator supports on digital radio frequencies circuitry.
9.RF filter.
RF filters of all types are required in a variety of applications from audio to RF and across the whole spectrum of frequencies. As such RF filters form an important element within a variety of scenarios, enabling the required frequencies to be passed through the circuit, while rejecting those that are not needed.
The ideal filter, whether it is a low pass, high pass, or band pass filter will exhibit no loss within the pass band, i.e. the frequencies below the cut off frequency. Then above this frequency in what is termed the stop band the filter will reject all signals.
Basic types of RF filter.
There
are four types of filter that can be defined. Each different type rejects or accepts signals in a different way, and by using the correct type of RF filter it is possible to accept the required signals and reject those that are not wanted.
The four basic types of RF filter are:
•Low pass filter
•High pass filter
•Band pass filter
•Band reject filter
As the names of these types of RF filter indicate, a low pass filter only allows frequencies below what is termed the cut off frequency through. This can also be thought of as a high reject filter as it rejects high frequencies. Similarly a high pass filter only allows signals through above the cut off frequency and rejects those below the cut off frequency. A band pass filter allows frequencies through within a given pass band. Finally the band reject filter rejects signals within a certain band. It can be particularly useful for rejecting a particular unwanted signal or set of signals falling within a given bandwidth.
10.DC-DC drivers and regulator.
DC to DC Regulators and Converters are packed in a tiny BGA (ball grid array) chips.
It used to convert, regulate and drives a certain amount of current-voltage.
It has the ability to stabilize, reduce or step up a voltage that feeds towards it.
in mobile phones it has a digital signal that been able to switch it on and off.
like for example it switch the LED lamp that used to light up the Display Screen while the cellphone is in used status and turn it off when the cellphone is not in use or at the sleep mode.
There are various kind and designed of these said components which according to each every purpose to the circuit. Sizes and bumps leads also have may differ with each other.
This chips may also damaged cause by a corrosive element or if a short circuit occurs.
11. Battery cell.
A back up battery cell or button cell is being used in cellphones circuit to back up the digital clock crystal oscillator. It used to maintain the clock at its real time status.
Its like when removing the battery of the mobile phone wont reset the settings of the digital clock that is being installed on a phone. Some phones without battery back-up like the old ones need to reset again after removing and replacing the battery. Its a big help to a digital circuits such high tech mobile phones circuit.
A battery cell is have two lead terminal which is negative and positive voltage output.
The metal can case of this type of battery is its positive (+) terminal, and the negative (-) terminal is the cap.
The negative is connected to a ground lines of a circuit while the positive is feed to a clock oscillator circuit. It has low power output voltage range from 1.5 volts to 3.5 volts. In mobile phones used about 3.3voltage output.
They are compact and have long life. They are usually a primary single cell with a nominal voltage between 1.5 and 3 volts. Common anode materials are zinc or lithium. Common cathode materials are manganese dioxide, silver oxide, carbon monofluoride, cupric oxide or oxygen from the air. Mercuric oxide batteries were formerly a common battery type but have been withdrawn from marketing due to their mercury content.
A back up battery may also damaged when due to degradation, corrosion and losses its voltage when being shorted or by liquids like water;
A damaged battery cell can be easily notice when a leakage occurs, its liquid chemical will flow out and can cause damages to a nearby components.
In a mobile phones you can determine when the back-up battery is weak, when try to set the time of the clock, then power it off and by removing the battery for a while and put it back again, when the clock stayed at its time where you set, it means that back-up battery is still working but, if it ask you to set the clock again it means that the back-up battery is not working.
12. Integrated Chip.
Integrated circuits, also called "chips", are electronic circuits where all the components (transistors, diodes, resistors and capacitors) has been manufactured in the surface of a thin substrate of semiconductor material.
Integrated circuit is designed to save extra space on modern electronics.
In electronics, an integrated circuit (also known as IC, microcircuit, microchip, silicon chip, or chip) is a miniaturized electronic circuit (consisting mainly of semiconductor devices, as well as passive components) that has been manufactured in the surface of a thin substrate of semiconductor material. Integrated circuits are used in almost all electronic equipment in use today and have revolutionized the world of electronics.
In mobile phones it is packed with each desired certain applications purpose like Power Management, Baseband Processor, Application Processor , Memory Storage, Audio Codecs, Bluetooth and Wi-Fi Ciruits.
Some large pack chips composed of many circuits and certain application both in-place in one packaging.
IC Chips are very delicate to handle with and troubleshoot if found faulty, it needs a little bit deep knowledge and understanding on how that chips works on a particular circuit. Experience is the best tool to handle with it.