CAN I EARN WITHOUT ANY HAVING COMPLETE TOOLS YET IN MOBILE PHONE REPAIR?

I just want to post this simple answers here of some new learners that keep asking me, on how to startearning from repair without any having complete repair tools yet at all.
Some beginners might think that fixing a defective phone might as well as too difficult to deal with.
So this is just a quick and simple answer for the above question.

Well, all I can say is that you can start from the scratch, there are so  many mobile phone technicians started from nothing and turned into something, I've been also started from scratch, way back 9 years ago, I repaired cell phones before that only an opening tools like T6 screwdriver and a tweezer on my working table.


Mission Repair

In cell phone repair, there are two types of failure to handle with; 
The software and the hardware related problem or failure issues.
Its not been a bit easy to determine which type of failure to deal with a faulty mobile phone indication, that is why many expert uses the method of checking its firmware first before considering that the problem lies on the hardware parts.
this method is by way of reading the mobile phones firmware by a way of using flashing or unlocking tools, then in by this method they can read the logs. This logs is firmware that composed of many codes, the logs can help to determine which part or components causes the problem. 

Some software problem related failure issues are of such the following indications, but also the failure lies on the hardware parts in mobile phone devices, like hang up on logo only, often restarted, contact service, contact retailer, contact service provider etc, unable to power up, or dead phone due to itsfirmware interruption and a lot more which can only explained by after check up process. 

For a beginners, these are the things you can do repair as a good way to start. 
Well, you can do repair by replacing broken LCD's, replacing a broken power ON/OFF switch, you can do repair minor problems such us ringer problem, not charging, mouthpiece microphone, earpiece speaker problems and more problems that is not necessarily needs a deep troubleshooting procedure. 
You can do that as well as it doesn't need any software tools to handle with. 
All you need is replacement spare parts, a guide on how to dismantle the handset and or a service manuals.

What about flashing and unlocking?
Flashing and unlocking is not hard and too difficult to deal with, it is because when you purchase a flashing or unlocking tools, the sellers or the resellers will provide a support for their product via online. I have a little bit guide on this blog but not too much, due to some blogging restrictions.
The sellers  will update and inform you from time to time which and what mobile phone handsets is newly supported and will work with.You can visit this forum for where they all hanged out.
The techniques in flashing and unlocking is that you have to be familiar with the software tools and also by reading of the logs and codes.

UNDERSTANDING HOW RF CIRCUIT WORKS ON CELL PHONES

In cell phone repair it is very helpful to understand how the RF circuits works , for this is a big help when
troubleshooting No signal problem issues.
RF stands for radio frequency , this frequency is used to  transmit and receive the data signals from a mobile phone.

Here's a brief explanation on how does RF circuit works on mobile phones. 
This is for GSM RF circuit only, although the WCDMA circuit and WI-FI circuit have similarity on this but I will try to explain both of it hereafter. 

See the block diagram below. Observe how the frequency data signal feeds from a certain parts of an RF circuit design. 
A breakdown or failure of each certain part will result to signal loss and the capability to generate, amplify, control , process, send and receive the desired radio frequency during transmission process.  


In mobile phones transmission there are two types of operation took place, the receiving operation and the transmitting operation.
In normal mode, RX part is always active in receiving operation the antenna switch is always open its gateway through to the RX circuit, It is always ready to receive and intercepts the radio waves and wait for the desired frequency signal to catch up.
During transmission like making a call or sending a text message the antenna switch will close the gateway of the RX and open the gateway of the TX in order not to interfere the data signal during transmission.
All data that has been receive and before to transmit or send, all this data signals are feeds to the baseband processor.

An explanation  of an RF Circuit Parts and what possible problems if a certain part is damaged. 

RF Receiver - ( RX radio receiver )
The rf receiver are called RX, this circuit is design to receives, and process the data signals from the airwaves during transmission process. A failure of this circuit will result to unable to receive data signal during transmission. 

RF Transmitter  - ( TX radio transmitter )
the rf transmitter are called TX which is the one that process, amplify  the data signals from a mobile phone .  
Once failed to initiate  a failure to transmit radio frequency signal, this will result to unable to send data signal during transmission. .

Power amplifier -  RF amplifier
The power amplifier is used to amplify, boost up the radio frequency signal before it feeds to the antenna before it thrown over the air waves during transmission. If damaged will result to signal loss, a dropping signal indication on the display.

The Antenna is used to intercepts and thrown the radio radio frequency in the air  during transmission
When electricity is "thrown" into the metal of an antenna, the metal reacts to the electricity at an atomic level in the form of a wave.
if damaged or due to a corroded terminal pads, will indicate and show a poor signal or low level frequency signal.

Antenna switch
The antenna switch is used as a gateway that controls and manage the frequency to pass through, it switch the RX frequency signal and TX frequency signal during transmission process. literally  the antenna is the signal catcher and likewise the signal thrower. If damaged the gateway to the antenna will be closed and result to network signal indication.  

Crystal oscillator
Generates a desired frequency that feeds to the RX and TX circuits. In mobile phones a Voltage controlled Oscillator (VCO) and Voltage Controlled Temperature Compensated Crystal Oscillator (VCTXO) is used in rf circuit. 
If damaged the RX and TX will not work and the RF cicuit is at full failure.

SAW filter 
Surface Acoustic Wave filter used as an rf synthesizer to purify  a desired level of frequency. If damaged result also to no network signal indication. 

An example of the  RF circuit components layout on a PCB board.

The rf circuit components are often covered with shielding metal case unlike the baseband processor parts which is oftentimes not. This is because frequency is very vulnerable with unwanted radio waves interference and destroys data signals. Using the shielding metal will minimize the radio waves interference.

For further questions just post a message on the shout box page.

UNDERSTANDING ABOUT BLUETOOTH CIRCUIT IN MOBILE PHONES, A KEY TO FIX BLUETOOTH PROBLEM ISSUES

We already know that Bluetooth is an open wireless device technology standard for exchanging data over short distances from fixed and mobile devices(using short wavelength radio transmissions), creating personal area networks (PANs) with high levels of security.The Bluetooth baseband protocol is a combination of circuit and packet switching. Slots can be reserved for synchronous packets. Each packet is transmitted in a different hop frequency. A packet nominally covers a single slot, but can be extended to cover up to five slots. Bluetooth can support an asynchronous data channel, up to three simultaneous synchronous voice channels, or a channel, which simultaneously supports asynchronous data and synchronous voice.
and that's how it simply  works.

Since we are talking about mobile phones here, it is much more really great to know how really bluetooth circuit works on cell phones circuit? Isn't it nice to know, so that we can easily managed how to fix it since it is our main reason in this tutorials by learning how to repair damaged cell phone devices. 
In mobile phones Bluetooth problems also occurs when the bluetooth circuit is damaged, Some new cell phone techie find it hard to fix bluetooth for not knowing how the circuit works.

Okay, lets tackle  it for a while in just very simple explanation so that all of those without any background in electronics  might can catch up too, and then we can use it in our everyday job on GSM field.

Figure the bluetooth circuit block diagram below for it shows how the Bluetooth Circuit works according to each corresponding parts or components that is being connected to it. 

Typical block diagram of a Bluetooth Circuit

The bluetooth transceiver module is packed into chip or IC (integrated circuit), this chip needs a certain power supply to make it work. All the data that has been transmit (send) and receive from the bluetooth antenna and bluetooth RF (radio frequency) transceiver  is feeds in for receiving and feeds out when sending to the application processor (cpu IC). There is an RF clock which comes from the RF circuit section is also feeds into it, that certain RF - Radio frequency is also needed by the bluetooth module to make it fully functional.

Since all those certain parts on bluetooth circuit were packed only into chips. A way to truly understand how does the circuit connect with each other from each certain components is by reading the circuit schematic diagram to locate this certain components parts on the main PCB board so that we can be able to check, trace and fix when a bluetooh failure happens. here's an example of the bluetoothschematic diagram and figure out how each components connect with other. In this method you can easily identify where that certain parts connected from one another.  See here:

And here's an example of the Bluetooth circuit  layout of components on a PCB board.
You'll notice that all of the bluetooth components is mounted in one section and near to each other. Some important spots is being labeled for quick troubleshooting guide. Like this picture below, the voltage supply and the RF clock are being labeled for quick check up and test procedures. 

The key reason with this is that when it comes fixing bluetooth problem issues is to check the supply voltage and the RF clock signal first before trying to check , test, replace any other corresponding components being connected within the whole bluetooth circuit.

For any further deeper questions just post it unto the chat box page.

UNDERSTANDING WLAN AND GPS CIRCUIT ON SMART PHONES

Additional features such as Bluetooth, WLAN and GPS on Smart phones become more popular in the market. As a techie you also need to figure out how this circuit works in order for you to catch up a new evolving designed on mobile  phones.

These additional features is packed into an IC component module in a circuit, and this kind of 
of circuit are associated with a master clock which typically a external clock crystal oscillator. 
With the master clock the data transmitted or received  is modulated to a proper certain frequency.

Here's how simply tells us how the circuit works on smart phones. 

The WLAN circuit
 Wireless Local Area Network (WLAN) links two or more devices using some wireless distribution method (typically spread-spectrum or OFDM  radio), and usually providing a connection through an access point to the wider internet. This gives users the mobility to move around within a local coverage area and still be connected to the network.

A typical block diagram below shows bluetooth wlan circuit, this block diagram will tell us how the clock oscillator feeds desired frequency to the WLAN module. The Wlan is associated is with the bluetooth transceiver circuit to send receive the data from the Wlan module to register it to the applicationprocessor.
In this diagram shows that the WLAN module also needs the RF clock to make it work, this RF clock comes from the RF circuit. In other designed aVoltage Controlled Temperature Compensated Crystal Oscillator(VCTXO) is used as an external clock generator. 

Typical block diagram of Bluetooth WLAN circuit

 

The GPS Circuit
The Global Positioning System (GPS) is a space-based global navigation satellite system that provides reliable location  and time information in all weather and at all times and anywhere on or near the Earth when and where there is an unobstructed line of sight to four or more GPS satellites.The GPS (global positioning system) circuit comes with a GPS module this is packed into chip, a GPS RX filter, GPS clock crystal oscillator and a GPS antenna. 
In this block diagram the GPS module is being feed with different RF clock data signal which also comes from the RF circuit. 

Typical block diagram of bluetooth with WLAN and GPS circuit

The components layout of Bluetooth, WLAN and GPS circuit on a PCB board.
This shows an example of the bluetooth circuit associated with WLAN and GPS circuit mounted on PCB board.

You'll figure out that all circuit components such as the ic oscillator, bluetooth chip, wlan chip and gps chip is mounted all together with each corresponding connections. The RF clock is  located on the RF circuit section which is comes from the RF chip.


And here's an schematic diagram of WLAN and GPS circuit, for knowing how the circuit components connected with each corresponding components.

This  is only a simple explanation how does the circuit works, the main key for this lesson is how to figure out and used this tutorial in troubleshooting and repairing GPS and WLAN problem and failures on a particular mobile phone devices, that we are going to tackle it here and so on...

UNDERSTANDING MOBILE PHONES REMOVABLE MEMORY CARD PINOUTS - FOR MEMORY CARD PROBLEMS AND FAILURE REPAIR

By learning how does the removable memory card works on mobile phone devices. We can easily configure on how to repair if something went wrong when the memory card related problems such as  memory card can't be read, memory card not detected and many other related memory card errors  on mobile phones occurred.

But first, we must also understand about removable memory cards and how it is being constructed.
In mobile phones there are three types of removable memory card being used the first was the SDcard which is so big in size used on some old model cell phones and then comes the MiniSD and the latest is the microSD card which the  smaller one and commonly used in most latest designs.

Secure Digital is what SD means, it is a flash based removable memory card. The card format may also be used other device functions in addition to data storage.

The SD card size dimensions are: 24mm wide x 32mm long. The standard width is 2.1mm, while the Thin SD Memory Card has a width 1.4mm. 

SD Card Pinout

Pin	Pin Name	SD Signal Function SD Mode	SPI Signal Function SPI Mode
1	DAT3/CS	Data Line 3	Chip Select/Slave Select [SS]
2	CMD/DI	Command Line	Master Out/Slave In [MOSI]
3	VSS1	Ground	Ground
4	Vdd	Voltage Supply [2.7v or 3.6v]	Voltage Supply [2.7v or 3.6v]
5	Clock	Clock	Clock [SCK]
6	Vss2	Ground	Ground
7	DAT0/D0	Data Line 0	Master In Slave Out [MISO]
8	DAT1/IRQ	Data Line 1	Unused or IRQ
9	DAT2/NC	Data Line 2	Unused

MiniSD Card is a type of Removable NAND flash memory card format. 
miniSD cards have memory capacities ranging from 256MB to 4GB. However, some of the capacity may be used for formatting and other functions, and not available for data storage. A miniSD card will fit in an SD card slot with a miniSD Adapter, miniSD Adaptes makes miniSD memory cards compatible with all SD-based devices. 
There are 3 speed grades: Class 2, 2MB/s, Class 4, 4MB/s and class 6 card, 6MB/s.

The MiniSD Card measures 20mm x 21.5mm and 1.4mm thick.

miniSD Pinout Configuration

Pin #	Pin Name	SD Signal Function SD Mode	SPI Signal Function SPI Mode
1	CD/DAT3	Chip Detect/Data Line 3	Chip Select
2	CMD	Command Line	Data In [DI]
3	VSS1	Ground	Ground
4	Vdd	Voltage Supply [2.7v or 3.6v]	Voltage Supply [2.7v or 3.6v]
5	Clock	Clock	Clock [SCK]
6	Vss2	Ground	Ground
7	DAT0	Data Line 0	Data Out [DO]
8	DAT1	Data Line 1	Unused
9	DAT2	Data Line 2	Unused
10	NC	For future use	For future use
11	NC	For future use	For future use

microSD Card is also a type of Removable NAND-type small flash memory card format, and has a dimensions of 11mm x 15mm and 1mm thick. MicroSD is short hand for Micro-Secure Digital [Transflash].

microSD Pinout, SD Mode

Pin #	Pin Name	Signal Function
1	DAT2	Data Bit 2
2	CD/DAT3	Card Detect / Data Bit 3
3	CMD	Command Line
4	Vdd	Supply Voltage 2.7v / 3.6v
5	CLK	Clock
6	Vss	Ground
7	DAT0	Data Bit 0
8	DAT1	Data Bit 1

microSD Pinout, SPI Mode

Pin #	Pin Name	Signal Function
1	NC	No Connect
2	/CS	Chip Select
3	DI	Master Out/Slave In (MOSI)
4	Vdd	Supply Voltage 2.7v / 3.6v
5	CLK	Clock
6	Vss	Ground
7	DO	Master In/Slave Out (MISO)
8	RSV	Reserved

Mobile phones manufacturers used  SD mode and SPI mode Memory card Signal Function, it  only varies according on mobile phones designed.  You can easily determine which one is SD mode or SPI mode designed. Just figure out the MMC slot socket then count the corresponding pins on it. In SD mode all pins has a connections while in SPI mode some of the pins are reserved and not in used or have no connection in the circuit.

In continuation of this post by learning how the Removable Memory Card Circuit works on mobile phones, and How to troubleshoot and repair memory card problem issues, we can configure which particular mobile phone used the SD mode and SPI Mode signal functions.