We are currently in the maintenance of mobile phone chipset MTK accounted for more than 70%, MTK chipset cheaper mobile phones, multi-functional, non-technical conditions are ripe, and so on, so that the bad cell phone is easy to repair, we are bringing the vitality, MTK chipset in the mobile phone We have a lot of maintenance is characterized by, first, with a high degree of integration, and the other is a small external components such as the characteristics of the MTK chipset to understand the principles, so that rivals and emerge victorious in every battle, the failure to determine quickly and decisively to deal with failure, Our maintenance staff over the course, I introduced the following I MTK chipset in the maintenance of maintenance experience and common principles and to learn and exchange experiences.
First, power
At present, there are two power MTK chips, the two chip MT6305 is a MT6318 is a function of their more or less the same as in our regular maintenance to see.
Power pin map
Power boot process
Press the button when the boot after the diode turn-on, control the keyboard to detect low-level output signal, power supply and integrated circuit opened the output voltage, power supply start-up circuit is to maintain the reset signal, power supply reduction after the beginning of the normal output voltage separate ways, entering Start software, completion of the boot.
1, equipped with batteries, battery-powered start. Press the start button, so that the IC power (MTK6305) 32 feet (MTK6318) of the K7 feet high into low post, CPU to be reset after power supply, 32.768KHZ vibration from the system clock, CPU work, CPU power to the (MT6305) of 24 feet (MT6318) of the foot F9 reset signal, power supply is to maintain continuous work.
Second,
MTK chipset does not boot repair
Phone start working conditions, continued normal phone to boot, take the following four conditions: First, the work of the normal power supply IC; Second, the normal work of the clock, and the third is the normal logic circuits, software is the work of the normal four.
1, the work of the normal power supply IC
(1) MTK normal power supply IC is that there is a voltage, that is, the battery voltage or external power supply;
(2) start trigger signal, MTK boot trigger signal is low, the boot trigger signal is sent to the IC power, press the start button in, the boot will have a trigger signal changes in the level of (change from the high Low).
(3) power supply IC integrated within the general group of more controlled or controlled regulator circuit, when the boot trigger signal when the IC power regulators should have multiple output voltage output.
Power 18 # (VMEM) = 2.8V, for the character.
Power 20 # (VDD) = 2.8V, for logic.
Power 22 # (VRTC) = 1.5V, for real-time clock circuit.
Power 24 # (RESET) = 2.8V, voltage reset
Power 25 # (VTCXO) = 2.8V, for crystal 13M # 4.
Power 27 # (AVDD) = 2.8V, for logic.
Power 30 # (VREF) = 1.3V, voltage reference.
Power 33 # (PWRBB) = 1.5V voltage to maintain the boot, the CPU through the C1 feet.
Power 48 # (VCORE) = 1.8V, for the CPU.
(4) to maintain the start signal from the CPU, power supply IC has been only start after the signal to maintain in order to maintain output voltage, or cell phones will not be able to continue to boot.
2, clock circuit
There are the normal system clock. CPU clock signal by the beat is the basis of data processing, mobile phone in the clock circuit, there are two: One is the clock VCO modules, including the oscillation circuit components and crystal. When the normal power supply connection, the self-oscillation, the formation of the output signal 26MHZ; and the other is the crystal frequency integrated circuits and components, the frequency IC to be an internal power supply after the crystal oscillator circuit for start-from-IF amplification module output. 26MHZ clock after a general capacitor, resistor or amplifier supply CPU, also the supply of radio-frequency phase-locked loop circuit as a basic clock signal.
3, logic and normal work
(1) there is the normal work of the power supply. Press the start button, power supply IC output stable power supply voltage logic supply, including the CPU, FLASH and the clock circuit.
(2) there is a normal reset signal when the CPU just for the power, its internal register in the random, not the normal operation procedure, CPU reset signal must be reset. Cell phones in the reduction of the CPU are generally low-end reduction, that is, to a certain period after the clock so that a variety of internal CPU registers cleared, and then here was another high voltage, so that the CPU run the program from scratch.
(3) the main logic circuits, including CPU, FLASH, CSP. When the CPU power available, the clock and reset the three conditions, the adoption of election-chip FLASH contact with the signal through the data bus and address bus to transmit data with each other.
(4) is a software phone CPU control of the boot and features a variety of procedures, the boot process and stored in FLASH set up within, MTK's early 6205,6217,6218,6219 such as CPU, such as FLASH data encryption does not, in the late 6223's, such as CPU , 6225,6226 BA, 6228,6230, and so are the FLASH data encryption, data is encrypted with the mobile phone models are not compatible. Therefore, if the wrong software or software may not cause the phone not to boot. Of course, the software may also be caused by abnormal network does not, does not indicate that dysfunction, death, and so many of the resumption of the boot failure.
4, power is not caused by the boot
Kin start by measuring whether the power supply voltage is 3.6V, output voltage in the power measurement is normal, there is no test reset signal output voltage 2.8V, is the maintenance of high voltage signal 2.8V.
(1) failure to maintain signal
When the boot by phone keys, control the keyboard to detect low-level output signal, power supply and integrated circuit opened the output voltage, power supply start-up circuit is to maintain the reset signal, if the CPU does not maintain the output signal can cause boot release button fault shutdown , This proved not to maintain the CPU to send the signal to reach the power supply can lead to the maintenance of normal working condition.
Approach
1, MT6305 power to check the first 33 feet, MT6318 first leg A9 have to maintain voltage, if there is proof voltage CPU has to maintain the voltage sent from the generally bad power failures, power-for troubleshooting.
2, check power MT6305 first 33 feet, MT6318 first leg A9 has no voltage if there is no CPU or worse caused by Xu Han, the first Canadian solder to the CPU or CPU processing or replacement for, such as CPU.
(2) based on current key start small
When the boot by building ammeter that only reflects the current 10MA, the CPU is obviously not working, check to the CPU power supply voltage (MT6305 first 48 feet and 18 feet) (MT6318 No. J10 feet and legs G1) voltage of 1.8V, 2.8 V is normal.
Approach
Caused by the start button is mainly due to the current small-26M clock circuit caused by work.
1, MT6305 power of 25 feet if there are voltage
2, MT6305 power of 25 feet to the power supply line if-26M
3, 26M crystal clock is bad
4, whether or not the normal work of the frequency or frequency caused by the bad.
4, the normal voltage does not boot (3.6V)
Battery does not start with the work of power supply voltage of 3.7V not boot, when the voltage of 4.5V to start a mobile phone.
Approach
(1) Check power supply voltage VBAT first MT6305 # 7, # 19, # 26, # 47 voltage is low voltage of 3V or so, check the MT6305 voltage VBAT feet + B to have a load resistance is aging, corrosion, caused by bad The failure, shorted resistance to the battery installed after the normal boot.
(2) of the power failure caused by bad in itself, for a troubleshooting.
(3) Check whether the phone plug end the phenomenon of corrosion caused by short circuit
5, rise to power in a few minutes after the start of the crash, restart
When the normal start or restart a while on death, the phone does not work.
(1) to the failure of such phenomena in general we are dealing with software maintenance, software is treated the same fault, I suspect that is not bad software, written in the next after the failure is still the same, I suspect that is not the CPU Xu Han-induced, I CPU and add character to carry out welding, or failure still, I began measuring the output voltage power supply, I found that MT6305 power supply voltage of only 48 feet voltage 1V, the normal voltage is 1.8V, I take Power put on a try, the boot is not normal and the resumption of the death.
Note: The phone does not start when we should pay attention to the maintenance of the power supply output voltage, output voltage power supply to our maintenance staff is a very important figure to be the normal power supply voltage, sufficient to prove the power of good or bad, so we Inspection failure to speed up the pace, not a waste of time.
Third, the keyboard light control circuit and maintenance
Boot normal mobile phone keypad, and other non-liang, the detection of light-emitting diodes found negative for the control voltage 2.8V, cathode voltage of 3.7V, control and the negative Yong Niezi to short-liang, such as a keyboard, light-emitting diode that is normal, a fault in the negative Control side, check the power of the MT6305 of 41 feet, 41 feet and control of light-emitting diode negative side of the load resistance between short-term, double-check by the board found that there are traces of corrosion extract, and found clear after the power supply board consists of a corrosion hole lost, With a copper wire from the power of the light-emitting diodes to fly 41 feet of negative resistance load control on the troubleshooting.
Description: In the cell phone repair, is also very important details, grasp the principles and details in the maintenance of improved speed to improve their technology.
Fourth, the background screen lights control circuit and maintenance
MT6318 background signal-controlled road map
Lights in the context of cell phone applications are two basic
(1) is a step-up control circuit is a series of light-emitting diodes
(2) Multi-level control is a control IC to complete the control IC can control the 4-way voltage 4 so that the light-emitting diode light at the same time can also control the two light emitting diodes, or 4-way control of voltage to make changes in the brightness light-emitting diodes Variable low.
(3) in the regular maintenance we met the background screen is not bright lights failure, the first point of failure detection, measurement screen whether there is a voltage lights, a lot of multi-class background of the screen to control the lights, multi-level control panel lights for the line with 3-5, or Pressure is controlled by two light-ray background of the screen, so that we can determine or control is a multi-stage step-up control of the background light of the screen.
(4) screen background light is not bright lights
1) the background screen measuring voltage lights are in working order, if we are in the normal general maintenance, ordinary reactionary screen background of the screen so that the lights off caused a lot of lines.
2) the background screen control IC bad light, can not find in the accessories, we can change the way to deal with the multi-level control of the K1, K2, K3, K4, such as linking to connect to VBAT (3.7V) voltage Side, A1 is a negative side control, separate from the keyboard light control negative side, the keyboard lights in general has a negative side to control the load resistance, from one foot to power it, this does not pass the background screens load resistance of the lights is the perfect .
3) step-up screen background light control, boost control circuit or a bad driver IC or step-up coil, such as bad, if not find a corresponding accessories, we can do the change of the solution to the background screen is not bright lights, we all know Screen background signal-controlled step-up circuit of the screen is a series of background light, he can be more than 12V voltage required to light up the 4 light-emitting diodes, we screen the background of the LED lights off, into a parallel, so that you can point voltage 3V It Liang, a positive VBAT (3.7V) voltage end of the cathode separate from the keyboard light control negative side, the keyboard lights in general has a negative side to control the load resistance, from one foot to power it, this does not load Resistance screen background lights of the perfect.
Fifth, the circuit card fault detection and repair
The basic principles of work
MTK chipset, CPU has to provide circuit card SIM card data and the start signal voltage, SINDATA data signals, SIMRST reset signal, SIMCLK clock signal, SIMVCC voltage control, respectively, to the power of (MT6305) 9 feet, 10 feet, 11 feet, 12 Feet, and so on, an integrated power conversion module SIM card switch, the CPU to control SIMVCC, when the 12-foot power supply voltage 2.8V, SIN card to open the power switch conversion module is (MT6305) Power of 8 feet to the beginning of SIM cards Power, 14 feet, 15 feet, 16 feet to start output signal SIM card, SIM card is working.
Repair process
First of all, check card connector, measuring card data sitting on the line to resistance, the resistance did not prove card connector and power connector or not caused by short-term, oscilloscope measurements in the boot of 2-3 seconds can be measured card signal waveform, If there is no proof of wave power is no signal output card, check the power supply, power measuring 12 feet to see whether provided by the CPU voltage waveform, a waveform prove bad for power supply, no waves caused by Xu Han check whether the CPU or the CPU and the power of Interruption caused by the line, if the disconnect between the CPU and power supply you can find on a 2.8V power supply voltage from 12 feet, the second 2-3 start in measuring the power of 8 feet, 14 feet, 15 feet, 16 feet Card connector or a normal wave.
1, does not recognize card
Immersion is a mobile phone, customer identification card used to say, I open the phone to see the Main Board, was found next to the card connector corrosion, with oscilloscope waveform measurement card connector, three signal lines are low voltage waveform of the leakage, Multimeter used to detect signals in the card-to-ground capacitance, capacitance-to-earth removed troubleshooting.
2, arising from the non-recognition software card
Boot normal phone also did not find any other anomalies that do not identify card, open the phone card connector on the measurement of resistance to normal, oscilloscope waveform measurements found no wave, was also considered to be caused by a bad power supply in the boot 2 -- 3 seconds measured 12 feet of power has not found 2.8V voltage power source in the 9 feet, 10 feet, 11 feet and no wave is not a bad CPU, CPU to try to add the following welding how to test failure Or do not recognize the same card, it is the CPU it does not work in our industry has a habit of maintenance, as appears to be a hardware failure to deal with the software that I was an on-line information was loaded into power after the card identification card boot A.
3, Power caused by the non-recognition card
Bad power supply caused by the non-recognition cards, not-for-power deal can not fault identification card, the principle is power, there are circuit switched data card, the card and control signals from the CPU, by the CPU to power the output power out there.
The following graphic
Power in the identification card is not bad, not-for-power can also get it in the power of 9 feet, 10 feet, 11 feet, and so on from the CPU card from the three signals were received on card connector, in taking on a 2.8V power supply Voltage in the power of 14 feet, 15 feet, 16 feet card output broken foot, boot test drive all the normal identification card, in the maintenance of two-phone card to be alone when they found the problem, not through the power card signal from the CPU card directly to the conversion on the circuit.
4, two-maintenance card non-circuit detection and identification card maintenance
Two-card to be double-or dual-card single question, and so on, in the maintenance and repair single-card mode, dual-CPU are two CPU at the same time, start-up in the main CPU when the first post-paid start in the CPU, through the power circuit card The output, dual-card to be double-or single-output power when there is a signal to the dual-card circuit card in the card connector from the CPU control, dual-CPU single-CPU and the difference is that the CPU's have a single card conversion circuit, so that Phone cards to achieve double-double to be double or single card to be a switch card or 2 cards work in our maintenance, especially in dual-CPU single card to be double-or single-card circuit to be the conversion module (MT6302) a lot of problems because he VBAT directly to a battery power supply is likely to result in high current, leakage, short circuit, and other damage.
5, double, single card is not to be identified cards 2
Customers use mobile phone customers by phone, said a fall below 2 does not recognize the card, check card to open the phone's 2-to-ground resistance is normal, with 2 card oscilloscope measurements found no power supply voltage waveform, a card in the power supply Card 2 feet from the boot test, 2 cards can work, as mobile phone system switch card and a card 2 also normal.
Sixth, testing and maintenance of radio frequency circuit
The straight drive often to see the built-in antenna, there are basically two kinds of built-in antenna.
Preface: mobile phone antenna must be selected frequency circuit board and the resistance, if not in strong signal when the normal communication in weak signal when the signal-to-call diving, no service call, such as intermittent failure in our maintenance in a lot of people do not Take note of this fact, often higher rates of mobile phone renovation.
1, the election-frequency antenna circuit
As we often say that maintenance is frequently the election circuit, according to the theory is that the antenna matching circuit, generally 75 or so in Europe, we have two common.
2, in order to better send and receive electromagnetic waves, the parallel resonant capacitor in the circuit boards of the two very open to inductance for the oscillator. Capacitive distribution to achieve compatibility, - the GSM-band EGSM (low-fat, higher 880 ~ 915 MHz and 925 ~ 960 MHz) plus DCS (issued 1 710 ~ 1 785 MHz, received 1805 ~ 1 885 MHz), total Antenna on the request for DualBand (880 ~ 960 MHz, 1 710 ~ 1 880 MHz). Therefore, there are two inductors for a sparse density of the coil to meet the two-frequency band to send to receive.
3, cell phone antenna matching, the radio frequency band signal circuits, as well as the band device duplex to the phone in a different band of radio frequency signals connected to the antenna. One of the radio frequency signal circuits, respectively, with corresponding matching circuit, making the radio-frequency signal circuit by the launch of the antenna, the antenna receiving the signal characteristics will not affect each other. See here, everyone should know that the antenna and antenna matching circuit principle, we often met in the maintenance of such a situation, MTK chipsets.
3, antenna switch to switch the role of the band, the separation of receiving, signals the launch, in many cases because we do not have time for the antenna switch will direct the short, but some models because the receiver, launching another signal interference can cause signal weak , When the signal-to-call diving in weak signal areas such as mobile phone service without fault.
4, note: R1 for the 100-200? resistor, Q1.Q2 the old antenna switch, is looking for two (fast diodes) can, working principle is the fast diode switches from the role, in order to receive control for low-end power Ping, the switch does not work, to receive signals transmitted directly to receive a filter, when fired high for the fast turn-on diodes, power amplifier output directly from the antenna to launch out to receive such a launch could signal an independent, non - Interference. Fast diode work with the general principle is the same as diodes, but ordinary diode switches in a state of the reverse recovery time is longer, about 4 ~ 5ms, can not meet the high-frequency switching circuits. Fast diode rectifier mainly used in high-frequency, high-frequency switching power supply, high-frequency RC snubber circuit, inverter circuits, and so on, the reverse recovery time of up to 10ns. Fast diode include fast recovery diode and Schottky diodes.
5, antenna and antenna switch, filters, and other common cause of failure
1, signals diving
2, weak signal
3, firing difficult
4, intermittent firing
5, no signal
6, firing off
7, found gateway machine
Trouble is, and so on and the antenna matching circuit caused about.
Seven, IF principle of supply and maintenance
1, MT6129 four-band transceiver channels, mainly in GSM850, E-GSM-900, DCS1800-PCS1900MHz its receiving circuit, including selective circuit, the circuit switch (antenna switching) filter circuits such as filtering, MT6129 chip integrated with the launch of the reception circuit And the frequency synthesizer circuit, to enlarge Clock circuit and so on, and there are MT6129 regulator modules radiofrequency, VBAT from 6129 to 3 feet and 15 feet to provide 3.8V voltage, CPU T1 by the output VCXOEN foot control signal to the 6129 14-foot control 6129 RF internal voltage regulator power supply circuit work, 4 feet by the output VCC-RF2.8V, 16-pin output VCC-SYN2.8V, power supply from 27 feet ADD2.8V power output of 6129 to 37 feet for the 6129 IQ module to provide power supply circuits.
2, MT6139 in the MT6129, based on the four-band transceiver channels, mainly in GSM850, E-GSM-900, DCS1800-PCS1900MHz its receiving circuit, including selective circuit, the circuit switch (antenna switching) filter circuits such as filtering, MT6139 chip With the launch of the reception circuit and frequency synthesizer circuit, AFC and the clock amplifier and so on, 26M crystal clock and the General MT6129, a different shock is not the same way, MT6129 is the power supply shocks after the production of 26M into the IF frequency, MT6139's 26M is a crystal clock circuit 26M have access to the frequency of the frequency, 26M crystal clock has no direct power supply to three feet of a grounding pin output, MT6139 RF power supply is a regulator and a separate module.
3, the experience of maintenance: no maintenance of the mobile phone signal, must be selective circuit, receiving circuit, firing circuit to keep clean, there is no other flux, as are the use of high-frequency radio frequency circuit original, this will result in no signal, weak signals, Signal diving, firing difficulties, such as network failure, mainly due to failures caused by the election of the inductor circuit frequency, high-frequency capacitance, and so on, or removed for cause and does not match the impedance of the antenna, then hit the difficulties caused by the main reason.
4, quickly determine fault, IF we receive a foot of a leave Inductor take on the antenna, IF output will then launch a false antenna and boot test machine to see whether there is a cell phone signal and launch, and so on, if there is evidence has-IF front-end Issues such as antenna switching, filter receiver, to receive high-frequency capacitance, power amplifier and so on. If there is no signal, we suspected IF, 26M, CPU, software, which is divided into two major pieces of failure to narrow the scope of the failures in maintenance-free radio frequency signals, such as failure to quickly determine the point of failure.
5, MT chipset RF circuit repair my own experience
MTK chipset, the RF part of the circuit's IC mainly IF two chips: MT6129; Second, the MT6139.
No quick to judge the signal, without firing, weak signals, such as failure to fight the emergency phone
First of all, we open the phone first look below to see some of the radio frequency.
1) to see whether the radio frequency part of the clean
2) to see there is no other maintenance personnel have been revised
3) to see there are no places Corrosion extract
4) view the mobile phone is not original or Shuaiguo out of a catch or not
5) Check more attention to further understand the scope of failure
6, Jin-free 288 phone signal
Reflected by the customer before January extract, is looking to open a mobile phone chipset MTK, the main version has traces of corrosion, oxidation spot some of the components or circuits, such as broken, first of all, after the board clean boot, the boot through the current reaction and There is no signal screen, we know that MTK is not installed in the phone cards as long as there is time to start signal will be displayed, by detecting frequency signal oscilloscope input waveform has received hopping signals that the fundamental frequency of normal, careful testing found that the filter And inductors are traces of corrosion, the filter inductance and scored from the boot after the welding display the signal to put on a network card can be called normal.
Experience: Immersion corrosion in the maintenance of the radio frequency circuit, in the absence of failure should not be found on the frequency, antenna switch, power amplifier to carry out additional raids like welding, which will lead to corrosion of the original off, disconnected lines, such as corrosion, Some components or a bad motherboard, you have to bring a long slow process of repair.
7, transit ZT886 dual-card-free cell phone signal
Customers are used to crash, the screen has been bad for the screen, the screen for no signal, no current search network, the radio frequency part of the inspection did not find any abnormality, by their own experience, the general crash is the big thing is that Easily broken or delayed, such as welding, I would let CPU plus welding, machine failure test remains the same, said customers in the absence of prior to the fall also can be used to fight a good answer the phone, I would like CPU is not a welding trailer to a CPU Cong Zhi-tin solder in the back after the test machine is not the same signal, this time I used the oscilloscope measurements to receive the signal frequency, intermediate frequency receiver in the foot after another antenna or no false signals in the frequency feet will then launch a false signal to the antenna or not, the blame It is not a bad frequency, for a first look, or the same frequency and the CPU is not a short-circuit or clock problem, 26M measuring voltage 2.8V, measured in the frequency 26M is also normal, think of all of a sudden on-line measurement never 26M This is not quasi-26.00000000M, previous online surveys are 25.900000000M-25.9999999999 about 26M to the frequency of such quasi-line test is not, except in the AFC can find out when disconnected, and then think of the AFC signal, 26M measurement 26M won the AFC on foot to prevent the infinite is that the CPU is no signal to the AFC on 26M, 26M fly CPU won control of the AFC feet, boot test machine had received a phone call signal normalized.
Experience
CPU output from the AFC automatic frequency control signals, to adjust the frequency of 26M to reach the intermediate frequency mixer circuit work needs to receive the signal frequency tracking and locking, follow-up phase with the lock, and so on, the frequency is in a stable, we 26M measurement when the AFC after the foot off the Quasi is a measurement.
8, there is no signal the launch
CECT-368 double-double to be mobile, use a folding machine to see the new machine Moyoudongguo, the cards are installed on two-out do not call the failure of the launch, both cards can access, CPU is the 6225A, is the frequency MT6139, is the power amplifier PF08155B, suspected amplifier is not broken or industrial problems in the first intermediate frequency on leave after another antenna, then try to call a normal machine, which has proved to be amplifier, first in the oscilloscope measurements found the net in the amplifier Industrial foot found weak voltage waveform is not caused by the CPU, find the cause of the problem is the industrial control signals are provided by the CPU, the CPU plus the following welding failure is still the same, it is a software problem, not many would like to format the following In that format after the failure is still the same, then the next in line to write data into a boot dual boot machine test cards can be a normal calls.
Experience: We have not launched to deal with the problem, first of all to watch whether the radio frequency part of the unusual circumstances, (refers to the abnormal situation, extract, corrosion, there are obvious components of the damage, etc.) If not, the following measuring frequency of firing pin and output Amplification of the Industrial feet to determine the scope of failure to gain a better understanding after the start in the repair, do not add to large areas of welding, which can cause unnecessary losses, a waste of time.
9, no signal
One customer used the T168 mobile phone, CPU is 6226BA, IF is MT6129C, power amplifier is the RF3146, to open a cell phone to see very much of the repair, said customers in the repair before the signal is also from time to time so that they do not repair the signal of At this time I board the radio frequency part of the cleansing of all the following, do not look at the filter is used to connect the line, when I boot test drive found the signal, the signal is the weakness of the test call was also normal, weak signal That is the filter problem, in other motherboard down on a filter 900M, welding machine on the test signal over the normal cells also fired, a happy heart, the capacity to pay the next day, said a customer came in the home did not signal a The signal to go out there, the antenna is not a good catch, open the phone antenna is detected, the antenna to receive a number of election-frequency circuit capacitors and inductors of the two did not, the problem is not caused by, so to get a large capacitors and inductors Welding up after the normal test drive, type the following for customers to go back, go back to the customer does not come, proved to be selected frequency antenna circuit does not match the rise in weak signal of the signal he did not, in strong signal when the signal is over The grid.
Experience: We repair to the attention of radio frequency part of some of the details, one antenna, the antenna is a selective circuit, is a three-antenna switch, is a four-filter attaches great importance to this, five radio frequency circuit to be clean.
Eight, MTK low power shutdown
1, low-voltage mobile phones will soon prompt start off, this time on his cell phone turned off, the phone is not turned on.
MTK in the cause of the CPU has two voltage detection pin is a high detection, is a low-level detection, when the CPU-D6 not detected when high, CPU as the initiative on low-voltage shutdown, MTK-CPU There MT6205, MT6217, MT6218 are generally 104 resistance, MT6219, the general CPU in the next two to do resistance testing voltage, MT6226, MT6225, MT6228-CPU power MT6305 in the use of the general resistance of the two has to do voltage detection, MT6226, MT6225, MT6228-CPU in 6318 the use of power, there is a direct power supply to provide the high voltage.
2, MTK low maintenance shutdown is about to experience:
1) General is about to shut down a lot of low-power CPU is caused by Xu Han. Canadian approach to welding Zhi Cong CPU or CPU.
2) The software also can cause bad low-power shutdown failure to deal with the following format or software, written from the heart, and other information.
3) Detection of exclusion (exclusion 104) caused by the bad low-power shutdown, for exclusion (General MT6205, MT6217, MT6218) with the more exclusive group.
4) MT6219, MT6225A, MT6226, MT6228, and other low-power shutdown is usually caused by bad testing resistance, resistance to replace.
5) MT6219, MT6225A, MT6226, MT6228, and other low-power shutdown resistance testing has not caused a lot of voltage, resistance is not bad, we can take on a 2.8V power supply voltage to give him the OK.
6) MT6219, MT6225A, MT6226, MT6228 use the power MTK6318 usually caused by a bad power supply, and some not-for-power can deal with failures, first of all, when we start to measure the power around and see that no large capacitor voltage, that is, MT6139 L4 the foot if they did not have a voltage when you are next to the measurement of capacitance voltage 2.8V if you can draw on his try-voltage, if we can rule out the possibility that failure to prove the feet, MTK6139 power output of a battery voltage detection In the next to the power supply filter capacitor, as long as it is to find the capacitor to a voltage of 2.8V can be resolved by a low-power shutdown fault.
Nine, microphone and earpiece circuit repair
1, the first measurement of whether the damage to the microphone, you can use digital multimeter 2K files, then transfer Hong Bi-positive, negative and total access, digital multimeter numerical display, and then his mouth, then Blow Digital Multimeter changes in the value of the show. Shows that normal microphone.
2, a lot of bad cell phone microphone main reason is that the extract caused by corrosion or broken.
3, microphone in the stand-by phone when there is no voltage, in a phone call can be measured when the microphone out of the cathode voltage of about 1.8V-2.8V voltage, if there is no measuring voltage or power supply may be disconnected resistance Caused by the bad.
4, in the phone call, the microphone cathode voltage is normal, then send or sent to the voice of small words such as failure, usually have a microphone circuit caused by the leakage, paying particular attention to the microphone circuit-to-ground capacitance, Capacitance-to-ground fault caused a lot of leakage.
5, send microphone, the normal voltage, through telephone touch method used to find the reasons for failure, in the open when the phone Yong Niezi iron or touch the original microphone circuit in the phone to hear whether or not you have a touch with the original voices reflect If there proved to be a transmitter circuit problem is the absence of audio processing system, MTK chipset is the integrated audio processor in the CPU in, CPU or bad, Xu Han, then send the rise.
6, then send the MTK chipset, is the largest number of failures, caused by the software, then send or send voice so small and so are a lot of failures, so we sent in maintenance, then failure to pay attention to a few points above it.
10, MTK receiver circuit
MTK receiver circuit is very simple, CPU integrates audio processing module, the handset has audio signal directly from the CPU out, we did not repair the handset in the voice of the first to use handset multimeter resistance measurement to determine whether good or bad handset, measuring in the main board of the handset A \ B resistance point to determine whether the motherboard caused by short-term, with 10,086 dial desk in the oscilloscope to measure when the handset on the motherboard A \ B point there is no sound waves to determine whether the CPU is the problem, CPU Zhi Cong and so on, or for Approach.
11, MTK chipset music IC enlarge
1, MTK chipset to enlarge the music has more than 10 kinds of IC, I, for example on a common double, a single-or two-channel music to enlarge IC maintenance mode, the amplification of music IC 8 feet to 9 feet, 9 feet of two hours is a central point is grounded, is a central point of access VBAT voltage, we often encounter problems in maintenance.
2, MTK chipset with integrated MP3 music processing module, CPU's T3 terminal control and A15, B15 two-channel output, output music to zoom zoom IC output out to see if it is simple to do with the very complex, the first music IC amplification is very small, pin-not grasp the direction, once the foot-fault caused by welding current, welding technology can not result in the following short-circuit, 9, called the amplification of music, there are two IC, you can board the IC measurement center Then the ground is still the power to determine what music you use the zoom IC, 9 feet of the center of IC and two feet or take over the earth, and other such power to tell a good direction. So if there is no music, first detected the following input in the amplification of music around the IC has resistors or capacitors in general is input, oscilloscope measurements there is no sound wave, there is evidence to enlarge IC bad music, such as the CPU has not requested additional welding and so on.
3, MTK chipset with integrated MP3 music processing module music noise distortion great failure to understand the principle point of amplifier, we know that in the amplifier input enter a weak signal, amplified by the amplifier output to the speakers that we can hear the Zhener Sound, if brought out the amplifier input, such as failure or leakage, there is the voice of the amplifier output or the exchange of voice, and so much noise, noise in general is not a big music amplification IC caused by the bad is to enlarge the input signal IC caused by the inspection found that music There are black corrosion input capacitance, capacitance to be replaced after the normal music.
4, musical sound glitch
Customers by phone before the show music sounds great, the next day when all of a sudden the voice of a small, as long as we maintain in the cloud is on the small voices, there is no music in general is a direct amplification of music-for-IC, I changed the music is still very small, is Music is not the IC input in question, I major in computer audio input line used to receive mobile phone music IC input, so that the mobile phone play music, but still small voice, touch Yong Niezi music of the IC input found Great voice, this proved not bad music IC, the fault lies with the input, MTK have a CPU chip output signal of the music is not a bad CPU, the first increase in the following welding that the increase after the welding boot normally play music music A.
Fault: small voices in music, music without fault in the first music of the IC input signal into a look at music is not-for-IC, if that is normal CPU failures.
5, software failures are not ringing music
The fault is obvious software fault, because there is ringing voice, play music is sound, first of all to deal with the following software format, or as the failure to find a later written into the information the OK.
Little experience maintain
Maintenance of our music to enlarge the IC, I used my side of the tool is a computer sound, the computer's audio input received phone music of the IC input Do not forget ground, so your mobile phone, play music, you have a computer Stereo sound on the come, so you can more easily determine the CPU is the music or the issue of the IC.
12, the keyboard circuit testing and maintenance experience
MTK chipset, the following points about the keyboard
1, main board-style keyboard
Main Board-keyboard, and is one of the main board, MTK chipsets used in cell phones, many are also many failures, the board-type keyboard, many shortcomings, we often use the keyboard, especially good people who send text messages, according to the hand in the keys Pressure on the board so that the deformation caused by malfunctioning keys, Xu Han components, do not start to operate when the lock button, and other failures, said the key MTK chipset is almost no protection circuit, there are only a few places on the capacitor, the button directly to the CPU-side control .
2, single-socket keyboard
Keyboard-Sockets alone, the fault often lies with the seat up and down, frequently used keys is likely to result in a failure of one or more key group of key failure of failure, the reasons for the frequent use of the keyboard so that the keyboard loose Block up and down link will appear after one or a combination of Failure of key failures.
3, single-cable connection
Single-cable connection of the few bad, that is caused, such as broken, extract, in the maintenance of regular activities, causing damage to the keyboard cable, etc.
4, welding alone cable -
Welding row a separate line and can easily block almost worse, because in the ordinary use of the keyboard, the keyboard up and down the activities of the growing gap, the keyboard cable in the welding on the Main Board of occlusion is scheduled to spend the tin so hard and soft row One line and exclusive line of the regular activities of the welding head so that row and resulted in disconnected phone lines between key one or a combination of buttons, such as failure of failure.
5, fault detection and maintenance of key
After many years of maintenance experience, I give you several ways to detect and repair.
6, all the key failure
We all know that all the key failure of the basic principles, that is, if you press a button fixed under the circumstances, CPU you receive the key signal has become a high after the low-level, CPU in the working conditions under the command button, so that all The keys can not be used, all the keys out of two is common, and extract key corrosion, two, caused by leakage.
Detection and repair
Immersion corrosion caused by the failure of all the keys.
1) Check whether there are key areas of corrosion
There are buttons found corrosion, to deal with the washing.
2) Check whether there are abnormal side buttons
Side buttons can be easily corrosion due to sweat easily into the hands of side buttons, side buttons is corrosion, clean-up and side buttons on the side buttons to capacitance.
3) Check the end of play there is no interface corrosion
In many MTK chipset interface plug on the end of every boot signals the end of play are also easy to damp, extract all the corrosion, to the end of play or to deal with cleaning out, and so on.
a) check whether the normal voltage measurement button
Voltage is a key to a 2.8V voltage 0V, if all the keys out, there is a set of keys or all of the normal voltage is not such a failure is the number of board leakage, one or more keys in the work of the state caused.
b) use the oscilloscope measurements is key leakage
Key leakage, to use the oscilloscope measurements, oscilloscope measurements show outside 2.8V-vpp in the test were found inside 1.6V-vpp voltage leakage, treatment, cleaning the Main Board, on the keyboard to removal of all the capacitor, such as
c) start testing the health 3.5V voltage is higher than the voltage
Boot health caused by the failure of all the keys, the power is on the boot or boot can not boot off, and other health problems by measuring voltage boot Kin 1 ------ 2.3V voltage, the boot is a health or leakage caused by short circuit , First of all, whether or not-for-normal power supply, clean interface plug the end of the phone, start looking for lines and so on.
d) failure caused by bad software
Software failures, telephone switching machine to normal when the caller is unable to show calls, all the keys out, the measurement of the normal voltage, there is no leakage, by the customer, said he had received the message after the shutdown, in the boot All the key failure to see that this is obviously the fault of software, software to deal with the normal start button.
e) CPU failure caused by bad
CPU caused by the failure of all the key fault, the voltage detection button, there is no leakage, both within and outside the circle button, but there are voltage, a 2.8V voltage inner ring, outer ring has a strange 2.6V voltage This is not a software problem, Failure to deal with the following software is still the same, the CPU to increase the welding Zhi Cong is also a good thing as failure is not a bad CPU, a CPU that really put the troubleshooting.
4, even from top to bottom approach Failure Block button
Block up and down keys out even the general cleaning is more than can be two under, a group of key failure in general is to fly a seat in the end-line approach has been my personal experience in handling such a high rate of the renovation, due to the extraordinary Button operation, the key up and down easily relaxed even block or bad, is your cleaning repaired, a few days, and other customers come back, buttons and a failure or other malfunction of the key group of customers was not pleased to say that you are not technical , The following in order to deal with all the fly line only clean, even the general up and down the block on the line with more than 10, if the fly line is up to half an hour to get, so that customers can use for a year or so, I found a lot of maintenance Such a phenomenon, there are other people in the repair of several customers after the repair to me, I saw on the board after I tell their clients that, you want to deal with a one-time cleaning or the following first, but if one-time deal with fly line is we Customers know the trouble you have a high level, you have a two birds with one stone.
13, cell phone charger circuit detection and repair
1, mobile phone charger did not fault the MTK chipset also many, charging IC is a charge of 3 feet to control the foot, when the IC charge of 3 feet to detect external power supply, the turn-on charge into the IC at the same time MT6305 power of 1 foot, charging IC No. 4 feet to control the charging ,7-8 feet and 4 feet of the power battery voltage detection, through the power of the 5-6 feet to the CPU, so that the CPU switch to state-of-charge on-screen display.
2, cell phones do not charge, the charge is more than bad IC or IC charge of the foot control did not receive any external power supply voltage caused by, or for IC rechargeable inspection to check the end of the phone plug, the charge of the IC is 3 feet and tail plug to connect to check power 2 feet high it is, in charge of checking power supply voltage of 4 feet, such as whether there is
3, the charger is connected charger failure has been removed for maintenance
Chargers have been in addition to the charger to connect, MT6305 power of the charge is 6 feet detect low-level output signal pin, CPU time as a low-level received in the state of charge, the charger is connected screen, the screen shows the battery charge, When the CPU when they received a low-level display charger has been removed, the screen showed the end of the charge.
See above you know the basic history of the fault, the charger is connected to remove the charger has the following can cause failure.
1) CPU caused by Xu Han
2) The power supply caused by Xu Han
3) charge caused by bad IC
4) Play the end of corrosion caused by
4, the charger is connected to remove the charger have been failures, first check to go to the end of the phone plug, charging IC, power supply, CPU and so on, you have to blindly increase welding CPU, I have been in the maintenance charger to connect the charger has been removed When found Xu Han CPU is not a lot of failures, once used as a mobile phone customers a day that the charger is connected to remove the charger has to occur once or twice been in charge at times, I thought might be caused by the CPU Xu Han , Opened on the phone to the CPU plus welding, after the end of the deal to customers, such as four or five days, said a customer came, or appeared in the same fault, I took the CPU to open his cell phone to see if the following CPU tin point Normal CPU to go back and start welding there is no charger is connected to remove the charger has a fault, then thought for a long time they get to know why no CPU below the spot did not find dead or Xuhan point, why the Chargers Has been to remove the charger to connect, why not add welding the CPU emerged, this time to return phone customers, ten days after the card unit is back, or failure, however, do not tell their clients that the last time Long, multi-frequency, let me make the following checks for him, I carefully opened the cell phone was found charging IC testing before the end of play and have some corrosion in particular, the end of the play is very serious corrosion inside, I gave him a thorough After cleaning, is Customer SAIC looks to me that you have the money to repair my bad back, I went to repair elsewhere, I'm still not say that all low-line customers away, two or On the customer does not, then I looked at the drawings to find a way to understand the principle of charging.
4, and different power MT6318
14, MTK touch-screen circuits and maintenance
1, MTK four-wire resistive touch screen theory
Touch-screen display attached to the surface, and monitors the use of line, if the measure could touch points on the screen coordinates of the location may be based on screen display coordinates corresponding to the content or icons Touch informed of the intention. Resistive touch screens which in embedded systems with the more. Resistance touch screen is a 4-story transparent screen film complex, the bottom is a glass or plexiglass composition of the grass-roots level, is the top layer of the outer surface after hardening in order to deal with smooth plastic coating layer, the middle is the two-conductive metal layer, At the grass-roots level and above the plastic layer on the surface, the two conductive layer between many of the small transparent separation point separating them. When the fingers touch screen, the two conductive layers in touch contact points. The touch screen of the two conductive metal layer is a touch-screen face two in each of the two ends of the face coated with a silver plastic, known as the face of a pair of electrodes, if a face on the last imposed on the electrode Voltage, then the work will be formed on the surface evenly in a row parallel to the voltage distribution. As shown in Figure 1, when the X in the direction of the electrode on the last imposed a determined voltage, and the Y direction of the electrode without voltage, in parallel to the X-voltage field, contact the Department voltage value in Y + (or Y -) Last Electrode reflected by measuring the Y + on the electrode voltage to the size of the contact will be aware of the X coordinates. By the same token, when the Y added to the electrode voltage to the electrodes X and not on the voltage, by measuring the X + voltage electrodes, the contacts will be aware of the Y coordinates.
2, four-wire resistance touch screen flaws:
Resistance touch screen to the B side is often touch, touch-screen four-resistance of the B side to adopt ITO, we know that, ITO is a thin metal oxide, used in the process, will soon have a small crack, and crack once, The original current flow through the line and forced around the crack, the uniform distribution of the resulting destruction of the voltage, there is a touch screen damage, cracks for the performance of the Department are not allowed to point. With the crack and the increased number of touch-screen will gradually expire, so life is not long four-wire touch screen resistance of the main issues.
3, domestic and imported touch-screen phone is the same as resistive touch screen is, we want to maintain a very easy substitution, as long as the same size touch screen can be a substitution, below the experience of several substitution.
Now many non-brand-name screen handwriting of a high failure rate, we also encountered a lot, and the following to share with you this experience in maintenance,
MTK touch-screen common arrangement
1) 4 line of touch-screen interface for the order of X + Y + X-Y -
2) touch-screen interface 4 line order for the X-Y-X + Y +
3) touch-screen interface 4 line for the order of X + X-Y + Y -
4) Line 4 touch-screen interface for the order of X + Y-X-Y +
5) touch-screen interface 4 line order for the Y + X-X + Y -
6) touch-screen interface 4 line order for the Y-X + X-Y +.
As we meet for regular maintenance of touch screen was a problem, in fact, very simple operating principle that he can be a horizontal Y +, Y-, is a vertical X +, X-in touch screen point of view, can not help but to trouble you The purchase of touch-screen, look at him the same, that is axial to the touch screen, so to connect OK.
4, software-induced failures are also a lot of touch-screen, we can determine how bad is the touch-screen software is bad, my own experience to tell you the following.
Software failures caused by the phenomenon of
Touch-screen software failures are many, there are several characteristics
1) according to the touch screen when the number of health by a 3, 4 by 6 by 7 by 9 or a 9 by 3 or 7, according to a 7 by 3 of 9 This is caused by axial reversed, tested in the touch-screen Inspection of limitations are not allowed to deal with software on OK.
2) The touch screen can not, we go to the four touch-screen measuring voltage, in the case of the net can be detected Y + and Y-voltage 2.8V or two X +, X-voltage, and so on, the touch-screen input and output axial Voltage line proved that touch-screen has not worse, if that is inconsistent with touch-screen does not work, we can deal with the software tested on the following OK.
3) caused by the software lock-axis, can only touch-screen horizontal or vertical can not live Eng vertical line, and so on, settle axial center, is the only touch-screen rather than pressing the center of the digital afterlife is pressed to 5 The other can not deal with software on OK.
5, touch-screen hardware failure caused by the phenomenon of
1) touch-screen is no obvious damage, there is no touch-screen click the reflect, touch-screen measuring voltage is only one of the voltage on the other yo yo 0:00 a few volts, and so on, are generally caused by the touch screen for.
2) touch-screen from time to time in writing or painting intermittent phenomenon occurs when short-term line, bending, alignment, and so on, can not use touch-screen or the lower part of the upper part could not be used, and so on, have a 1.40 touch screen angle can not be used or not, c. And so on with.
3) points in the touch-screen screen from time to time does not reflect the trend, that is not reflected in the menu and so on.
More than a few of my personal experience, so you can quickly determine it is a software failure caused by hardware failure or failures, our maintenance staff is first-line speed is money, speed is a technical difference.
Five-Year Plan, the headset mode detection and repair
1, headset models are basically in a headset interface, or the end of the phone plug failures, is a multi-extract, corrosion, the end of a bad play, bad blocks caused by the headset. We repair the failure of the headset mode, it is necessary to double-check interface circuit, with million will be used to measure voltage switch and headphone Block work, and some MTK chipset design of the conversion circuit and control circuit and so on, CPU Xu Han failure caused by bad or very The small, we often see in the maintenance of software failures, and so on.
2, headphone model is CPU-controlled, CPU-MT6226BA-V1 is the control of foot feet, CPU-V1 is a foot high ban on low-level control, repairs so that we found in the headset mode, the CPU in the foot V1 Voltage 2.8V to add it.
3, headset mode rapid approach
Sent by mobile phone customers that the calls can be silent is to screen a headset symbol on my heart to understand, to open a cell phone to see some amendments, I asked the customers over there, said the amendment did not fix I did not say if the second pick up the phone motherboard, look for one with fine copper wire, copper wire in the degree of tin, with Feng Qiang 6226BA-CPU to the heating, found in a 6226BA-CPU than the CPU to find the foot of the V1 The location of fine copper wire into the power supply to find a 2.8V voltage connect, try booting the machine OK.
Description: In the same maintenance over the phone, do not fix fault is not so good looking, so if you have experienced, then according to your own experience to deal with failure, this is also to save time, save the trouble of checking, it is necessary to quickly and Decisively deal with.
16, the same way memory card and maintenance
1, circuit card is simple, from 4 to send a data clock signal, the main storage is read, when we start the mobile phone in a state of memory card inserted (card control signal into a high-low) cell phone screen Show or SD card has been inserted, such as pull-out tips, we do not often find in the maintenance of identification cards, a lot of failures in the card connector, a variety of memory card blocks, the most closed-end cards is a bad seat.
2, does not recognize card
Customers use the phone that I do not put the MP3, the following can help me, I do not recognize a memory card, open the phone is closed check card Block, SD card in the deck, I also start to identify the cards I check the back seat was found the following card connector has a control switch card, MCINS switch to connect and, when inserted into the card to time, MCINS into a low-level mobile phones have been prompted to insert SD card, and so on, I MCINS Yong Niezai feet and Then the screen showed the SD card has been inserted in the phone when you start out, or insert SD card mobile phone screen is not prompted, insert the SD card when the SD card does not reset the phone system, there will be no SD card inserted, if the shutdown in the boot on the SD card Identified, we should not overlook the maintenance of the SD card switch.
3, does not recognize card
The same is used to open the phone, measuring multimeter card Block 8 of the line-to-ground resistance and found no abnormal, start to do the measurement card 8 voltage line 6 has 2.8V voltage, there is a Grounding, is a clock signal to start in 2-3 seconds when measuring the SD card so the clock has not found foot-voltage voltage, SD card clock in the foot or boot MCINS switch detects when there are SD cards, not detected SD card in the 2-3 seconds from low into high, the clock appeared to be caused by circuit problems! After checking on the Main Board found that while there is a row of resistors and capacitors are dirty black surface, cleaning the following are found in several other countries have corrosion resistance and capacitance, capacitance measurement is one end there are two ends of the earth, the capacitor in the boot removed after the test drive SD card The normal work.
17, circuit camera and maintenance
Camera principle
CPU integrated video camera and processing systems, such as drive, CPU and camera data signals are 8-10 months, the CPU is based on the model itself and the camera set, when the mobile phone into the system to take photographs or video, there is a power of 2.8 V voltage, CPU out of the reset signal so that the camera reset for data transmission at the same time to start working into the camera.
Camera fault maintenance
We often found in maintenance, installation is not ready to spend camera, camera Screen of Death, to take photographs when dark color display screen, photographed in the picture there is time to preserve the image, save pictures and no image is black, non-screen display, such as failure , To introduce the following my own experience in maintenance.
1, the camera itself bad failures
Device is not ready to spend camera, camera Screen of Death, to take photographs when dark color display screen, photographed in the picture there is time to preserve the image, save pictures and no image is a black camera, and so bad in itself caused by failure
2, the device is not ready
Bad software, CPU or bad virtual defend, the camera does not cause the power supply.
Device is not ready when we met a lot of maintenance, we write a new version of the information wrong, that is not camera data will also be installed in place not to drive caused by the camera, the software can also cause bad device is not ready, We usually deal with the case could be a multi-media format, CPU or bad virtual defend also caused many, CPU with 25 lines to the camera, there will be a line break caused by camera failure.
3, ZT288 cell phone, camera does not come out as the screen, the screen is black, but as the picture is normal, I saw very curious, this failure is rare, especially in our maintenance is rare in general do not fault Easily move the Main Board, the maintenance of our instinct, on first look at the following format, or failure, on-line under the months to write the information into the open the boot after the camera images on the screen already had it.
4, the two do not use peer-fault camera phone, I open the board to see all the action again, there is an extract phone, camera, said peers have replaced or failure, so that the camera itself is not the problem , Open the phone to start repair, extract the cell phone in the main board, ultrasound clear that the pre-Taiwan, to look at the camera had no problem connecting Block, to start in the camera when the power supply voltage measurement is also normal, surveying connectivity Block the line of resistance to two found no resistance, is not empty my feet on the main board of the camera block out the traces of corrosion were found on board the black spot is dead, after cleaning by welding back seat The camera installed boot test drive a normal camera. Taiwan has been fixed in the amendment that Taiwan, from ultrasound, drying out after the test cameras installed, this is also normal, not a repair.
Experience: In our maintenance, pay attention to details can not be ignored, he lost, in particular those details to save you time and take up the same phone they are not repair all the big move is basically over, You must do to gain the upper hand on the details of your maintenance to improve the speed, but also to improve your technique.
18, decryption software and processing software
6226BA just in the times listed, we do not have decryption technology, is no way to repair 6226BA phone chips, the beginning of a lot of online users to read out the information on the forum, you can not write the information exchange that is not written into the boot, Information is encrypted, and that many times on the phone to the same body lying there, not a very good way, and so there is only a tool to crack, this time in my dedicated researched the beginning of the decryption technology, did not engage in a few days out Understand that no matter is not filled or emptied into FF address above can not solve the problem of decryption, in a fortuitous opportunity to have a customer used a mobile phone that I often look at the crash was anything wrong, I can open a cell phone is 6226BA The CPU I have a silly, I really 6226BA the CPU is the encryption software can not write, I have to tell customers that your phone is a software problem to deal with software, customers deal with a unified software, I gave the customer-processing software, said there are risks Some cell phone encryption is to write the software will not boot, said that customers do not you write can not write, I ran several of the maintenance shop are saying that there is no way to deal with you on this can be, you write the At this time I said you have to deal with the information needs of mobile phone a few days, the reunification of the customer, so I feel pleased but not show, I can study the following 6226BA encryption issue, because I still have a few phone did not start the 6226BA is also a CPU and his The same, so let the customer on study of the following well here. Customers can use the phone boot, the boot after a crash on the night I put the phone customer information read out by 48 after a month in the online information is not written into the boot, a boot or not, information is really Encrypted so mysterious it, I used a tool to open source data did not look to see what the beginning of a problem discovered by a few to see all the information found in the Department F00000 node. F00000 after I cleared all the information in ten FF is a six-band in the sense of space, in the decimal metric system equal to F, 255, written after the filling into the phone after only a half-day boot, the boot can be
With the normal use of the death is not, this is a new discovery, filled with new information or not boot, is not the original data, there is no decryption code out to understand, just to rest, the operator will be able to fix one, A few days later I found an on-line information and I have not found information on phone model and CPU, the same font type, I put him down in the evening I write this new information has been lying in more than a month of cell phone , The phone did not expect the boot, 6226BA the start of the CPU, I am very surprised I had the original data and information on the following comparison 7M basically the same 7M after a lot of different, I do not like the pre-7M code coverage to the original data Years after the start or not, I also found the following on the Internet have been used to break free from the machine-readable information and I like that I wrote into the boot or not, when I found that I was under the information has been declassified information I previously tried under the new information and contrast the following information is in a section 7M ago and a few other characters do not like no other, I do not like the comparison over a period of the code to cover new information, Written on the cell phone after the boot screen Tang Liang does not reflect the following after the beginning of the ammeter and not the same as the previous 40MA about the current fixed there is some Jishi Miao ammeter to move the following 20MA to 40MA to boot, I have Carefully check the source code to narrow the scope, coverage to the new address information in paragraph 48 after written into the boot of the success of the test machine, start the mobile phone, equipped with card as soon as possible a normal test drive, I was excited, happy night did not break , And two mobile phones, I found a new on-line information, the beginning of the new information not found on this abandoned, and later data also found that the two get.
This is not a story to tell you, this is my cell phone access to decrypt the beginning of the study, since then, their research has been on the phone's data encryption issues to the present, their pay has also brought rich fruit.
Good deposit from SamOnline.
First, power
At present, there are two power MTK chips, the two chip MT6305 is a MT6318 is a function of their more or less the same as in our regular maintenance to see.
Power pin map
Power boot process
Press the button when the boot after the diode turn-on, control the keyboard to detect low-level output signal, power supply and integrated circuit opened the output voltage, power supply start-up circuit is to maintain the reset signal, power supply reduction after the beginning of the normal output voltage separate ways, entering Start software, completion of the boot.
1, equipped with batteries, battery-powered start. Press the start button, so that the IC power (MTK6305) 32 feet (MTK6318) of the K7 feet high into low post, CPU to be reset after power supply, 32.768KHZ vibration from the system clock, CPU work, CPU power to the (MT6305) of 24 feet (MT6318) of the foot F9 reset signal, power supply is to maintain continuous work.
Second,
MTK chipset does not boot repair
Phone start working conditions, continued normal phone to boot, take the following four conditions: First, the work of the normal power supply IC; Second, the normal work of the clock, and the third is the normal logic circuits, software is the work of the normal four.
1, the work of the normal power supply IC
(1) MTK normal power supply IC is that there is a voltage, that is, the battery voltage or external power supply;
(2) start trigger signal, MTK boot trigger signal is low, the boot trigger signal is sent to the IC power, press the start button in, the boot will have a trigger signal changes in the level of (change from the high Low).
(3) power supply IC integrated within the general group of more controlled or controlled regulator circuit, when the boot trigger signal when the IC power regulators should have multiple output voltage output.
Power 18 # (VMEM) = 2.8V, for the character.
Power 20 # (VDD) = 2.8V, for logic.
Power 22 # (VRTC) = 1.5V, for real-time clock circuit.
Power 24 # (RESET) = 2.8V, voltage reset
Power 25 # (VTCXO) = 2.8V, for crystal 13M # 4.
Power 27 # (AVDD) = 2.8V, for logic.
Power 30 # (VREF) = 1.3V, voltage reference.
Power 33 # (PWRBB) = 1.5V voltage to maintain the boot, the CPU through the C1 feet.
Power 48 # (VCORE) = 1.8V, for the CPU.
(4) to maintain the start signal from the CPU, power supply IC has been only start after the signal to maintain in order to maintain output voltage, or cell phones will not be able to continue to boot.
2, clock circuit
There are the normal system clock. CPU clock signal by the beat is the basis of data processing, mobile phone in the clock circuit, there are two: One is the clock VCO modules, including the oscillation circuit components and crystal. When the normal power supply connection, the self-oscillation, the formation of the output signal 26MHZ; and the other is the crystal frequency integrated circuits and components, the frequency IC to be an internal power supply after the crystal oscillator circuit for start-from-IF amplification module output. 26MHZ clock after a general capacitor, resistor or amplifier supply CPU, also the supply of radio-frequency phase-locked loop circuit as a basic clock signal.
3, logic and normal work
(1) there is the normal work of the power supply. Press the start button, power supply IC output stable power supply voltage logic supply, including the CPU, FLASH and the clock circuit.
(2) there is a normal reset signal when the CPU just for the power, its internal register in the random, not the normal operation procedure, CPU reset signal must be reset. Cell phones in the reduction of the CPU are generally low-end reduction, that is, to a certain period after the clock so that a variety of internal CPU registers cleared, and then here was another high voltage, so that the CPU run the program from scratch.
(3) the main logic circuits, including CPU, FLASH, CSP. When the CPU power available, the clock and reset the three conditions, the adoption of election-chip FLASH contact with the signal through the data bus and address bus to transmit data with each other.
(4) is a software phone CPU control of the boot and features a variety of procedures, the boot process and stored in FLASH set up within, MTK's early 6205,6217,6218,6219 such as CPU, such as FLASH data encryption does not, in the late 6223's, such as CPU , 6225,6226 BA, 6228,6230, and so are the FLASH data encryption, data is encrypted with the mobile phone models are not compatible. Therefore, if the wrong software or software may not cause the phone not to boot. Of course, the software may also be caused by abnormal network does not, does not indicate that dysfunction, death, and so many of the resumption of the boot failure.
4, power is not caused by the boot
Kin start by measuring whether the power supply voltage is 3.6V, output voltage in the power measurement is normal, there is no test reset signal output voltage 2.8V, is the maintenance of high voltage signal 2.8V.
(1) failure to maintain signal
When the boot by phone keys, control the keyboard to detect low-level output signal, power supply and integrated circuit opened the output voltage, power supply start-up circuit is to maintain the reset signal, if the CPU does not maintain the output signal can cause boot release button fault shutdown , This proved not to maintain the CPU to send the signal to reach the power supply can lead to the maintenance of normal working condition.
Approach
1, MT6305 power to check the first 33 feet, MT6318 first leg A9 have to maintain voltage, if there is proof voltage CPU has to maintain the voltage sent from the generally bad power failures, power-for troubleshooting.
2, check power MT6305 first 33 feet, MT6318 first leg A9 has no voltage if there is no CPU or worse caused by Xu Han, the first Canadian solder to the CPU or CPU processing or replacement for, such as CPU.
(2) based on current key start small
When the boot by building ammeter that only reflects the current 10MA, the CPU is obviously not working, check to the CPU power supply voltage (MT6305 first 48 feet and 18 feet) (MT6318 No. J10 feet and legs G1) voltage of 1.8V, 2.8 V is normal.
Approach
Caused by the start button is mainly due to the current small-26M clock circuit caused by work.
1, MT6305 power of 25 feet if there are voltage
2, MT6305 power of 25 feet to the power supply line if-26M
3, 26M crystal clock is bad
4, whether or not the normal work of the frequency or frequency caused by the bad.
4, the normal voltage does not boot (3.6V)
Battery does not start with the work of power supply voltage of 3.7V not boot, when the voltage of 4.5V to start a mobile phone.
Approach
(1) Check power supply voltage VBAT first MT6305 # 7, # 19, # 26, # 47 voltage is low voltage of 3V or so, check the MT6305 voltage VBAT feet + B to have a load resistance is aging, corrosion, caused by bad The failure, shorted resistance to the battery installed after the normal boot.
(2) of the power failure caused by bad in itself, for a troubleshooting.
(3) Check whether the phone plug end the phenomenon of corrosion caused by short circuit
5, rise to power in a few minutes after the start of the crash, restart
When the normal start or restart a while on death, the phone does not work.
(1) to the failure of such phenomena in general we are dealing with software maintenance, software is treated the same fault, I suspect that is not bad software, written in the next after the failure is still the same, I suspect that is not the CPU Xu Han-induced, I CPU and add character to carry out welding, or failure still, I began measuring the output voltage power supply, I found that MT6305 power supply voltage of only 48 feet voltage 1V, the normal voltage is 1.8V, I take Power put on a try, the boot is not normal and the resumption of the death.
Note: The phone does not start when we should pay attention to the maintenance of the power supply output voltage, output voltage power supply to our maintenance staff is a very important figure to be the normal power supply voltage, sufficient to prove the power of good or bad, so we Inspection failure to speed up the pace, not a waste of time.
Third, the keyboard light control circuit and maintenance
Boot normal mobile phone keypad, and other non-liang, the detection of light-emitting diodes found negative for the control voltage 2.8V, cathode voltage of 3.7V, control and the negative Yong Niezi to short-liang, such as a keyboard, light-emitting diode that is normal, a fault in the negative Control side, check the power of the MT6305 of 41 feet, 41 feet and control of light-emitting diode negative side of the load resistance between short-term, double-check by the board found that there are traces of corrosion extract, and found clear after the power supply board consists of a corrosion hole lost, With a copper wire from the power of the light-emitting diodes to fly 41 feet of negative resistance load control on the troubleshooting.
Description: In the cell phone repair, is also very important details, grasp the principles and details in the maintenance of improved speed to improve their technology.
Fourth, the background screen lights control circuit and maintenance
MT6318 background signal-controlled road map
Lights in the context of cell phone applications are two basic
(1) is a step-up control circuit is a series of light-emitting diodes
(2) Multi-level control is a control IC to complete the control IC can control the 4-way voltage 4 so that the light-emitting diode light at the same time can also control the two light emitting diodes, or 4-way control of voltage to make changes in the brightness light-emitting diodes Variable low.
(3) in the regular maintenance we met the background screen is not bright lights failure, the first point of failure detection, measurement screen whether there is a voltage lights, a lot of multi-class background of the screen to control the lights, multi-level control panel lights for the line with 3-5, or Pressure is controlled by two light-ray background of the screen, so that we can determine or control is a multi-stage step-up control of the background light of the screen.
(4) screen background light is not bright lights
1) the background screen measuring voltage lights are in working order, if we are in the normal general maintenance, ordinary reactionary screen background of the screen so that the lights off caused a lot of lines.
2) the background screen control IC bad light, can not find in the accessories, we can change the way to deal with the multi-level control of the K1, K2, K3, K4, such as linking to connect to VBAT (3.7V) voltage Side, A1 is a negative side control, separate from the keyboard light control negative side, the keyboard lights in general has a negative side to control the load resistance, from one foot to power it, this does not pass the background screens load resistance of the lights is the perfect .
3) step-up screen background light control, boost control circuit or a bad driver IC or step-up coil, such as bad, if not find a corresponding accessories, we can do the change of the solution to the background screen is not bright lights, we all know Screen background signal-controlled step-up circuit of the screen is a series of background light, he can be more than 12V voltage required to light up the 4 light-emitting diodes, we screen the background of the LED lights off, into a parallel, so that you can point voltage 3V It Liang, a positive VBAT (3.7V) voltage end of the cathode separate from the keyboard light control negative side, the keyboard lights in general has a negative side to control the load resistance, from one foot to power it, this does not load Resistance screen background lights of the perfect.
Fifth, the circuit card fault detection and repair
The basic principles of work
MTK chipset, CPU has to provide circuit card SIM card data and the start signal voltage, SINDATA data signals, SIMRST reset signal, SIMCLK clock signal, SIMVCC voltage control, respectively, to the power of (MT6305) 9 feet, 10 feet, 11 feet, 12 Feet, and so on, an integrated power conversion module SIM card switch, the CPU to control SIMVCC, when the 12-foot power supply voltage 2.8V, SIN card to open the power switch conversion module is (MT6305) Power of 8 feet to the beginning of SIM cards Power, 14 feet, 15 feet, 16 feet to start output signal SIM card, SIM card is working.
Repair process
First of all, check card connector, measuring card data sitting on the line to resistance, the resistance did not prove card connector and power connector or not caused by short-term, oscilloscope measurements in the boot of 2-3 seconds can be measured card signal waveform, If there is no proof of wave power is no signal output card, check the power supply, power measuring 12 feet to see whether provided by the CPU voltage waveform, a waveform prove bad for power supply, no waves caused by Xu Han check whether the CPU or the CPU and the power of Interruption caused by the line, if the disconnect between the CPU and power supply you can find on a 2.8V power supply voltage from 12 feet, the second 2-3 start in measuring the power of 8 feet, 14 feet, 15 feet, 16 feet Card connector or a normal wave.
1, does not recognize card
Immersion is a mobile phone, customer identification card used to say, I open the phone to see the Main Board, was found next to the card connector corrosion, with oscilloscope waveform measurement card connector, three signal lines are low voltage waveform of the leakage, Multimeter used to detect signals in the card-to-ground capacitance, capacitance-to-earth removed troubleshooting.
2, arising from the non-recognition software card
Boot normal phone also did not find any other anomalies that do not identify card, open the phone card connector on the measurement of resistance to normal, oscilloscope waveform measurements found no wave, was also considered to be caused by a bad power supply in the boot 2 -- 3 seconds measured 12 feet of power has not found 2.8V voltage power source in the 9 feet, 10 feet, 11 feet and no wave is not a bad CPU, CPU to try to add the following welding how to test failure Or do not recognize the same card, it is the CPU it does not work in our industry has a habit of maintenance, as appears to be a hardware failure to deal with the software that I was an on-line information was loaded into power after the card identification card boot A.
3, Power caused by the non-recognition card
Bad power supply caused by the non-recognition cards, not-for-power deal can not fault identification card, the principle is power, there are circuit switched data card, the card and control signals from the CPU, by the CPU to power the output power out there.
The following graphic
Power in the identification card is not bad, not-for-power can also get it in the power of 9 feet, 10 feet, 11 feet, and so on from the CPU card from the three signals were received on card connector, in taking on a 2.8V power supply Voltage in the power of 14 feet, 15 feet, 16 feet card output broken foot, boot test drive all the normal identification card, in the maintenance of two-phone card to be alone when they found the problem, not through the power card signal from the CPU card directly to the conversion on the circuit.
4, two-maintenance card non-circuit detection and identification card maintenance
Two-card to be double-or dual-card single question, and so on, in the maintenance and repair single-card mode, dual-CPU are two CPU at the same time, start-up in the main CPU when the first post-paid start in the CPU, through the power circuit card The output, dual-card to be double-or single-output power when there is a signal to the dual-card circuit card in the card connector from the CPU control, dual-CPU single-CPU and the difference is that the CPU's have a single card conversion circuit, so that Phone cards to achieve double-double to be double or single card to be a switch card or 2 cards work in our maintenance, especially in dual-CPU single card to be double-or single-card circuit to be the conversion module (MT6302) a lot of problems because he VBAT directly to a battery power supply is likely to result in high current, leakage, short circuit, and other damage.
5, double, single card is not to be identified cards 2
Customers use mobile phone customers by phone, said a fall below 2 does not recognize the card, check card to open the phone's 2-to-ground resistance is normal, with 2 card oscilloscope measurements found no power supply voltage waveform, a card in the power supply Card 2 feet from the boot test, 2 cards can work, as mobile phone system switch card and a card 2 also normal.
Sixth, testing and maintenance of radio frequency circuit
The straight drive often to see the built-in antenna, there are basically two kinds of built-in antenna.
Preface: mobile phone antenna must be selected frequency circuit board and the resistance, if not in strong signal when the normal communication in weak signal when the signal-to-call diving, no service call, such as intermittent failure in our maintenance in a lot of people do not Take note of this fact, often higher rates of mobile phone renovation.
1, the election-frequency antenna circuit
As we often say that maintenance is frequently the election circuit, according to the theory is that the antenna matching circuit, generally 75 or so in Europe, we have two common.
2, in order to better send and receive electromagnetic waves, the parallel resonant capacitor in the circuit boards of the two very open to inductance for the oscillator. Capacitive distribution to achieve compatibility, - the GSM-band EGSM (low-fat, higher 880 ~ 915 MHz and 925 ~ 960 MHz) plus DCS (issued 1 710 ~ 1 785 MHz, received 1805 ~ 1 885 MHz), total Antenna on the request for DualBand (880 ~ 960 MHz, 1 710 ~ 1 880 MHz). Therefore, there are two inductors for a sparse density of the coil to meet the two-frequency band to send to receive.
3, cell phone antenna matching, the radio frequency band signal circuits, as well as the band device duplex to the phone in a different band of radio frequency signals connected to the antenna. One of the radio frequency signal circuits, respectively, with corresponding matching circuit, making the radio-frequency signal circuit by the launch of the antenna, the antenna receiving the signal characteristics will not affect each other. See here, everyone should know that the antenna and antenna matching circuit principle, we often met in the maintenance of such a situation, MTK chipsets.
3, antenna switch to switch the role of the band, the separation of receiving, signals the launch, in many cases because we do not have time for the antenna switch will direct the short, but some models because the receiver, launching another signal interference can cause signal weak , When the signal-to-call diving in weak signal areas such as mobile phone service without fault.
4, note: R1 for the 100-200? resistor, Q1.Q2 the old antenna switch, is looking for two (fast diodes) can, working principle is the fast diode switches from the role, in order to receive control for low-end power Ping, the switch does not work, to receive signals transmitted directly to receive a filter, when fired high for the fast turn-on diodes, power amplifier output directly from the antenna to launch out to receive such a launch could signal an independent, non - Interference. Fast diode work with the general principle is the same as diodes, but ordinary diode switches in a state of the reverse recovery time is longer, about 4 ~ 5ms, can not meet the high-frequency switching circuits. Fast diode rectifier mainly used in high-frequency, high-frequency switching power supply, high-frequency RC snubber circuit, inverter circuits, and so on, the reverse recovery time of up to 10ns. Fast diode include fast recovery diode and Schottky diodes.
5, antenna and antenna switch, filters, and other common cause of failure
1, signals diving
2, weak signal
3, firing difficult
4, intermittent firing
5, no signal
6, firing off
7, found gateway machine
Trouble is, and so on and the antenna matching circuit caused about.
Seven, IF principle of supply and maintenance
1, MT6129 four-band transceiver channels, mainly in GSM850, E-GSM-900, DCS1800-PCS1900MHz its receiving circuit, including selective circuit, the circuit switch (antenna switching) filter circuits such as filtering, MT6129 chip integrated with the launch of the reception circuit And the frequency synthesizer circuit, to enlarge Clock circuit and so on, and there are MT6129 regulator modules radiofrequency, VBAT from 6129 to 3 feet and 15 feet to provide 3.8V voltage, CPU T1 by the output VCXOEN foot control signal to the 6129 14-foot control 6129 RF internal voltage regulator power supply circuit work, 4 feet by the output VCC-RF2.8V, 16-pin output VCC-SYN2.8V, power supply from 27 feet ADD2.8V power output of 6129 to 37 feet for the 6129 IQ module to provide power supply circuits.
2, MT6139 in the MT6129, based on the four-band transceiver channels, mainly in GSM850, E-GSM-900, DCS1800-PCS1900MHz its receiving circuit, including selective circuit, the circuit switch (antenna switching) filter circuits such as filtering, MT6139 chip With the launch of the reception circuit and frequency synthesizer circuit, AFC and the clock amplifier and so on, 26M crystal clock and the General MT6129, a different shock is not the same way, MT6129 is the power supply shocks after the production of 26M into the IF frequency, MT6139's 26M is a crystal clock circuit 26M have access to the frequency of the frequency, 26M crystal clock has no direct power supply to three feet of a grounding pin output, MT6139 RF power supply is a regulator and a separate module.
3, the experience of maintenance: no maintenance of the mobile phone signal, must be selective circuit, receiving circuit, firing circuit to keep clean, there is no other flux, as are the use of high-frequency radio frequency circuit original, this will result in no signal, weak signals, Signal diving, firing difficulties, such as network failure, mainly due to failures caused by the election of the inductor circuit frequency, high-frequency capacitance, and so on, or removed for cause and does not match the impedance of the antenna, then hit the difficulties caused by the main reason.
4, quickly determine fault, IF we receive a foot of a leave Inductor take on the antenna, IF output will then launch a false antenna and boot test machine to see whether there is a cell phone signal and launch, and so on, if there is evidence has-IF front-end Issues such as antenna switching, filter receiver, to receive high-frequency capacitance, power amplifier and so on. If there is no signal, we suspected IF, 26M, CPU, software, which is divided into two major pieces of failure to narrow the scope of the failures in maintenance-free radio frequency signals, such as failure to quickly determine the point of failure.
5, MT chipset RF circuit repair my own experience
MTK chipset, the RF part of the circuit's IC mainly IF two chips: MT6129; Second, the MT6139.
No quick to judge the signal, without firing, weak signals, such as failure to fight the emergency phone
First of all, we open the phone first look below to see some of the radio frequency.
1) to see whether the radio frequency part of the clean
2) to see there is no other maintenance personnel have been revised
3) to see there are no places Corrosion extract
4) view the mobile phone is not original or Shuaiguo out of a catch or not
5) Check more attention to further understand the scope of failure
6, Jin-free 288 phone signal
Reflected by the customer before January extract, is looking to open a mobile phone chipset MTK, the main version has traces of corrosion, oxidation spot some of the components or circuits, such as broken, first of all, after the board clean boot, the boot through the current reaction and There is no signal screen, we know that MTK is not installed in the phone cards as long as there is time to start signal will be displayed, by detecting frequency signal oscilloscope input waveform has received hopping signals that the fundamental frequency of normal, careful testing found that the filter And inductors are traces of corrosion, the filter inductance and scored from the boot after the welding display the signal to put on a network card can be called normal.
Experience: Immersion corrosion in the maintenance of the radio frequency circuit, in the absence of failure should not be found on the frequency, antenna switch, power amplifier to carry out additional raids like welding, which will lead to corrosion of the original off, disconnected lines, such as corrosion, Some components or a bad motherboard, you have to bring a long slow process of repair.
7, transit ZT886 dual-card-free cell phone signal
Customers are used to crash, the screen has been bad for the screen, the screen for no signal, no current search network, the radio frequency part of the inspection did not find any abnormality, by their own experience, the general crash is the big thing is that Easily broken or delayed, such as welding, I would let CPU plus welding, machine failure test remains the same, said customers in the absence of prior to the fall also can be used to fight a good answer the phone, I would like CPU is not a welding trailer to a CPU Cong Zhi-tin solder in the back after the test machine is not the same signal, this time I used the oscilloscope measurements to receive the signal frequency, intermediate frequency receiver in the foot after another antenna or no false signals in the frequency feet will then launch a false signal to the antenna or not, the blame It is not a bad frequency, for a first look, or the same frequency and the CPU is not a short-circuit or clock problem, 26M measuring voltage 2.8V, measured in the frequency 26M is also normal, think of all of a sudden on-line measurement never 26M This is not quasi-26.00000000M, previous online surveys are 25.900000000M-25.9999999999 about 26M to the frequency of such quasi-line test is not, except in the AFC can find out when disconnected, and then think of the AFC signal, 26M measurement 26M won the AFC on foot to prevent the infinite is that the CPU is no signal to the AFC on 26M, 26M fly CPU won control of the AFC feet, boot test machine had received a phone call signal normalized.
Experience
CPU output from the AFC automatic frequency control signals, to adjust the frequency of 26M to reach the intermediate frequency mixer circuit work needs to receive the signal frequency tracking and locking, follow-up phase with the lock, and so on, the frequency is in a stable, we 26M measurement when the AFC after the foot off the Quasi is a measurement.
8, there is no signal the launch
CECT-368 double-double to be mobile, use a folding machine to see the new machine Moyoudongguo, the cards are installed on two-out do not call the failure of the launch, both cards can access, CPU is the 6225A, is the frequency MT6139, is the power amplifier PF08155B, suspected amplifier is not broken or industrial problems in the first intermediate frequency on leave after another antenna, then try to call a normal machine, which has proved to be amplifier, first in the oscilloscope measurements found the net in the amplifier Industrial foot found weak voltage waveform is not caused by the CPU, find the cause of the problem is the industrial control signals are provided by the CPU, the CPU plus the following welding failure is still the same, it is a software problem, not many would like to format the following In that format after the failure is still the same, then the next in line to write data into a boot dual boot machine test cards can be a normal calls.
Experience: We have not launched to deal with the problem, first of all to watch whether the radio frequency part of the unusual circumstances, (refers to the abnormal situation, extract, corrosion, there are obvious components of the damage, etc.) If not, the following measuring frequency of firing pin and output Amplification of the Industrial feet to determine the scope of failure to gain a better understanding after the start in the repair, do not add to large areas of welding, which can cause unnecessary losses, a waste of time.
9, no signal
One customer used the T168 mobile phone, CPU is 6226BA, IF is MT6129C, power amplifier is the RF3146, to open a cell phone to see very much of the repair, said customers in the repair before the signal is also from time to time so that they do not repair the signal of At this time I board the radio frequency part of the cleansing of all the following, do not look at the filter is used to connect the line, when I boot test drive found the signal, the signal is the weakness of the test call was also normal, weak signal That is the filter problem, in other motherboard down on a filter 900M, welding machine on the test signal over the normal cells also fired, a happy heart, the capacity to pay the next day, said a customer came in the home did not signal a The signal to go out there, the antenna is not a good catch, open the phone antenna is detected, the antenna to receive a number of election-frequency circuit capacitors and inductors of the two did not, the problem is not caused by, so to get a large capacitors and inductors Welding up after the normal test drive, type the following for customers to go back, go back to the customer does not come, proved to be selected frequency antenna circuit does not match the rise in weak signal of the signal he did not, in strong signal when the signal is over The grid.
Experience: We repair to the attention of radio frequency part of some of the details, one antenna, the antenna is a selective circuit, is a three-antenna switch, is a four-filter attaches great importance to this, five radio frequency circuit to be clean.
Eight, MTK low power shutdown
1, low-voltage mobile phones will soon prompt start off, this time on his cell phone turned off, the phone is not turned on.
MTK in the cause of the CPU has two voltage detection pin is a high detection, is a low-level detection, when the CPU-D6 not detected when high, CPU as the initiative on low-voltage shutdown, MTK-CPU There MT6205, MT6217, MT6218 are generally 104 resistance, MT6219, the general CPU in the next two to do resistance testing voltage, MT6226, MT6225, MT6228-CPU power MT6305 in the use of the general resistance of the two has to do voltage detection, MT6226, MT6225, MT6228-CPU in 6318 the use of power, there is a direct power supply to provide the high voltage.
2, MTK low maintenance shutdown is about to experience:
1) General is about to shut down a lot of low-power CPU is caused by Xu Han. Canadian approach to welding Zhi Cong CPU or CPU.
2) The software also can cause bad low-power shutdown failure to deal with the following format or software, written from the heart, and other information.
3) Detection of exclusion (exclusion 104) caused by the bad low-power shutdown, for exclusion (General MT6205, MT6217, MT6218) with the more exclusive group.
4) MT6219, MT6225A, MT6226, MT6228, and other low-power shutdown is usually caused by bad testing resistance, resistance to replace.
5) MT6219, MT6225A, MT6226, MT6228, and other low-power shutdown resistance testing has not caused a lot of voltage, resistance is not bad, we can take on a 2.8V power supply voltage to give him the OK.
6) MT6219, MT6225A, MT6226, MT6228 use the power MTK6318 usually caused by a bad power supply, and some not-for-power can deal with failures, first of all, when we start to measure the power around and see that no large capacitor voltage, that is, MT6139 L4 the foot if they did not have a voltage when you are next to the measurement of capacitance voltage 2.8V if you can draw on his try-voltage, if we can rule out the possibility that failure to prove the feet, MTK6139 power output of a battery voltage detection In the next to the power supply filter capacitor, as long as it is to find the capacitor to a voltage of 2.8V can be resolved by a low-power shutdown fault.
Nine, microphone and earpiece circuit repair
1, the first measurement of whether the damage to the microphone, you can use digital multimeter 2K files, then transfer Hong Bi-positive, negative and total access, digital multimeter numerical display, and then his mouth, then Blow Digital Multimeter changes in the value of the show. Shows that normal microphone.
2, a lot of bad cell phone microphone main reason is that the extract caused by corrosion or broken.
3, microphone in the stand-by phone when there is no voltage, in a phone call can be measured when the microphone out of the cathode voltage of about 1.8V-2.8V voltage, if there is no measuring voltage or power supply may be disconnected resistance Caused by the bad.
4, in the phone call, the microphone cathode voltage is normal, then send or sent to the voice of small words such as failure, usually have a microphone circuit caused by the leakage, paying particular attention to the microphone circuit-to-ground capacitance, Capacitance-to-ground fault caused a lot of leakage.
5, send microphone, the normal voltage, through telephone touch method used to find the reasons for failure, in the open when the phone Yong Niezi iron or touch the original microphone circuit in the phone to hear whether or not you have a touch with the original voices reflect If there proved to be a transmitter circuit problem is the absence of audio processing system, MTK chipset is the integrated audio processor in the CPU in, CPU or bad, Xu Han, then send the rise.
6, then send the MTK chipset, is the largest number of failures, caused by the software, then send or send voice so small and so are a lot of failures, so we sent in maintenance, then failure to pay attention to a few points above it.
10, MTK receiver circuit
MTK receiver circuit is very simple, CPU integrates audio processing module, the handset has audio signal directly from the CPU out, we did not repair the handset in the voice of the first to use handset multimeter resistance measurement to determine whether good or bad handset, measuring in the main board of the handset A \ B resistance point to determine whether the motherboard caused by short-term, with 10,086 dial desk in the oscilloscope to measure when the handset on the motherboard A \ B point there is no sound waves to determine whether the CPU is the problem, CPU Zhi Cong and so on, or for Approach.
11, MTK chipset music IC enlarge
1, MTK chipset to enlarge the music has more than 10 kinds of IC, I, for example on a common double, a single-or two-channel music to enlarge IC maintenance mode, the amplification of music IC 8 feet to 9 feet, 9 feet of two hours is a central point is grounded, is a central point of access VBAT voltage, we often encounter problems in maintenance.
2, MTK chipset with integrated MP3 music processing module, CPU's T3 terminal control and A15, B15 two-channel output, output music to zoom zoom IC output out to see if it is simple to do with the very complex, the first music IC amplification is very small, pin-not grasp the direction, once the foot-fault caused by welding current, welding technology can not result in the following short-circuit, 9, called the amplification of music, there are two IC, you can board the IC measurement center Then the ground is still the power to determine what music you use the zoom IC, 9 feet of the center of IC and two feet or take over the earth, and other such power to tell a good direction. So if there is no music, first detected the following input in the amplification of music around the IC has resistors or capacitors in general is input, oscilloscope measurements there is no sound wave, there is evidence to enlarge IC bad music, such as the CPU has not requested additional welding and so on.
3, MTK chipset with integrated MP3 music processing module music noise distortion great failure to understand the principle point of amplifier, we know that in the amplifier input enter a weak signal, amplified by the amplifier output to the speakers that we can hear the Zhener Sound, if brought out the amplifier input, such as failure or leakage, there is the voice of the amplifier output or the exchange of voice, and so much noise, noise in general is not a big music amplification IC caused by the bad is to enlarge the input signal IC caused by the inspection found that music There are black corrosion input capacitance, capacitance to be replaced after the normal music.
4, musical sound glitch
Customers by phone before the show music sounds great, the next day when all of a sudden the voice of a small, as long as we maintain in the cloud is on the small voices, there is no music in general is a direct amplification of music-for-IC, I changed the music is still very small, is Music is not the IC input in question, I major in computer audio input line used to receive mobile phone music IC input, so that the mobile phone play music, but still small voice, touch Yong Niezi music of the IC input found Great voice, this proved not bad music IC, the fault lies with the input, MTK have a CPU chip output signal of the music is not a bad CPU, the first increase in the following welding that the increase after the welding boot normally play music music A.
Fault: small voices in music, music without fault in the first music of the IC input signal into a look at music is not-for-IC, if that is normal CPU failures.
5, software failures are not ringing music
The fault is obvious software fault, because there is ringing voice, play music is sound, first of all to deal with the following software format, or as the failure to find a later written into the information the OK.
Little experience maintain
Maintenance of our music to enlarge the IC, I used my side of the tool is a computer sound, the computer's audio input received phone music of the IC input Do not forget ground, so your mobile phone, play music, you have a computer Stereo sound on the come, so you can more easily determine the CPU is the music or the issue of the IC.
12, the keyboard circuit testing and maintenance experience
MTK chipset, the following points about the keyboard
1, main board-style keyboard
Main Board-keyboard, and is one of the main board, MTK chipsets used in cell phones, many are also many failures, the board-type keyboard, many shortcomings, we often use the keyboard, especially good people who send text messages, according to the hand in the keys Pressure on the board so that the deformation caused by malfunctioning keys, Xu Han components, do not start to operate when the lock button, and other failures, said the key MTK chipset is almost no protection circuit, there are only a few places on the capacitor, the button directly to the CPU-side control .
2, single-socket keyboard
Keyboard-Sockets alone, the fault often lies with the seat up and down, frequently used keys is likely to result in a failure of one or more key group of key failure of failure, the reasons for the frequent use of the keyboard so that the keyboard loose Block up and down link will appear after one or a combination of Failure of key failures.
3, single-cable connection
Single-cable connection of the few bad, that is caused, such as broken, extract, in the maintenance of regular activities, causing damage to the keyboard cable, etc.
4, welding alone cable -
Welding row a separate line and can easily block almost worse, because in the ordinary use of the keyboard, the keyboard up and down the activities of the growing gap, the keyboard cable in the welding on the Main Board of occlusion is scheduled to spend the tin so hard and soft row One line and exclusive line of the regular activities of the welding head so that row and resulted in disconnected phone lines between key one or a combination of buttons, such as failure of failure.
5, fault detection and maintenance of key
After many years of maintenance experience, I give you several ways to detect and repair.
6, all the key failure
We all know that all the key failure of the basic principles, that is, if you press a button fixed under the circumstances, CPU you receive the key signal has become a high after the low-level, CPU in the working conditions under the command button, so that all The keys can not be used, all the keys out of two is common, and extract key corrosion, two, caused by leakage.
Detection and repair
Immersion corrosion caused by the failure of all the keys.
1) Check whether there are key areas of corrosion
There are buttons found corrosion, to deal with the washing.
2) Check whether there are abnormal side buttons
Side buttons can be easily corrosion due to sweat easily into the hands of side buttons, side buttons is corrosion, clean-up and side buttons on the side buttons to capacitance.
3) Check the end of play there is no interface corrosion
In many MTK chipset interface plug on the end of every boot signals the end of play are also easy to damp, extract all the corrosion, to the end of play or to deal with cleaning out, and so on.
a) check whether the normal voltage measurement button
Voltage is a key to a 2.8V voltage 0V, if all the keys out, there is a set of keys or all of the normal voltage is not such a failure is the number of board leakage, one or more keys in the work of the state caused.
b) use the oscilloscope measurements is key leakage
Key leakage, to use the oscilloscope measurements, oscilloscope measurements show outside 2.8V-vpp in the test were found inside 1.6V-vpp voltage leakage, treatment, cleaning the Main Board, on the keyboard to removal of all the capacitor, such as
c) start testing the health 3.5V voltage is higher than the voltage
Boot health caused by the failure of all the keys, the power is on the boot or boot can not boot off, and other health problems by measuring voltage boot Kin 1 ------ 2.3V voltage, the boot is a health or leakage caused by short circuit , First of all, whether or not-for-normal power supply, clean interface plug the end of the phone, start looking for lines and so on.
d) failure caused by bad software
Software failures, telephone switching machine to normal when the caller is unable to show calls, all the keys out, the measurement of the normal voltage, there is no leakage, by the customer, said he had received the message after the shutdown, in the boot All the key failure to see that this is obviously the fault of software, software to deal with the normal start button.
e) CPU failure caused by bad
CPU caused by the failure of all the key fault, the voltage detection button, there is no leakage, both within and outside the circle button, but there are voltage, a 2.8V voltage inner ring, outer ring has a strange 2.6V voltage This is not a software problem, Failure to deal with the following software is still the same, the CPU to increase the welding Zhi Cong is also a good thing as failure is not a bad CPU, a CPU that really put the troubleshooting.
4, even from top to bottom approach Failure Block button
Block up and down keys out even the general cleaning is more than can be two under, a group of key failure in general is to fly a seat in the end-line approach has been my personal experience in handling such a high rate of the renovation, due to the extraordinary Button operation, the key up and down easily relaxed even block or bad, is your cleaning repaired, a few days, and other customers come back, buttons and a failure or other malfunction of the key group of customers was not pleased to say that you are not technical , The following in order to deal with all the fly line only clean, even the general up and down the block on the line with more than 10, if the fly line is up to half an hour to get, so that customers can use for a year or so, I found a lot of maintenance Such a phenomenon, there are other people in the repair of several customers after the repair to me, I saw on the board after I tell their clients that, you want to deal with a one-time cleaning or the following first, but if one-time deal with fly line is we Customers know the trouble you have a high level, you have a two birds with one stone.
13, cell phone charger circuit detection and repair
1, mobile phone charger did not fault the MTK chipset also many, charging IC is a charge of 3 feet to control the foot, when the IC charge of 3 feet to detect external power supply, the turn-on charge into the IC at the same time MT6305 power of 1 foot, charging IC No. 4 feet to control the charging ,7-8 feet and 4 feet of the power battery voltage detection, through the power of the 5-6 feet to the CPU, so that the CPU switch to state-of-charge on-screen display.
2, cell phones do not charge, the charge is more than bad IC or IC charge of the foot control did not receive any external power supply voltage caused by, or for IC rechargeable inspection to check the end of the phone plug, the charge of the IC is 3 feet and tail plug to connect to check power 2 feet high it is, in charge of checking power supply voltage of 4 feet, such as whether there is
3, the charger is connected charger failure has been removed for maintenance
Chargers have been in addition to the charger to connect, MT6305 power of the charge is 6 feet detect low-level output signal pin, CPU time as a low-level received in the state of charge, the charger is connected screen, the screen shows the battery charge, When the CPU when they received a low-level display charger has been removed, the screen showed the end of the charge.
See above you know the basic history of the fault, the charger is connected to remove the charger has the following can cause failure.
1) CPU caused by Xu Han
2) The power supply caused by Xu Han
3) charge caused by bad IC
4) Play the end of corrosion caused by
4, the charger is connected to remove the charger have been failures, first check to go to the end of the phone plug, charging IC, power supply, CPU and so on, you have to blindly increase welding CPU, I have been in the maintenance charger to connect the charger has been removed When found Xu Han CPU is not a lot of failures, once used as a mobile phone customers a day that the charger is connected to remove the charger has to occur once or twice been in charge at times, I thought might be caused by the CPU Xu Han , Opened on the phone to the CPU plus welding, after the end of the deal to customers, such as four or five days, said a customer came, or appeared in the same fault, I took the CPU to open his cell phone to see if the following CPU tin point Normal CPU to go back and start welding there is no charger is connected to remove the charger has a fault, then thought for a long time they get to know why no CPU below the spot did not find dead or Xuhan point, why the Chargers Has been to remove the charger to connect, why not add welding the CPU emerged, this time to return phone customers, ten days after the card unit is back, or failure, however, do not tell their clients that the last time Long, multi-frequency, let me make the following checks for him, I carefully opened the cell phone was found charging IC testing before the end of play and have some corrosion in particular, the end of the play is very serious corrosion inside, I gave him a thorough After cleaning, is Customer SAIC looks to me that you have the money to repair my bad back, I went to repair elsewhere, I'm still not say that all low-line customers away, two or On the customer does not, then I looked at the drawings to find a way to understand the principle of charging.
4, and different power MT6318
14, MTK touch-screen circuits and maintenance
1, MTK four-wire resistive touch screen theory
Touch-screen display attached to the surface, and monitors the use of line, if the measure could touch points on the screen coordinates of the location may be based on screen display coordinates corresponding to the content or icons Touch informed of the intention. Resistive touch screens which in embedded systems with the more. Resistance touch screen is a 4-story transparent screen film complex, the bottom is a glass or plexiglass composition of the grass-roots level, is the top layer of the outer surface after hardening in order to deal with smooth plastic coating layer, the middle is the two-conductive metal layer, At the grass-roots level and above the plastic layer on the surface, the two conductive layer between many of the small transparent separation point separating them. When the fingers touch screen, the two conductive layers in touch contact points. The touch screen of the two conductive metal layer is a touch-screen face two in each of the two ends of the face coated with a silver plastic, known as the face of a pair of electrodes, if a face on the last imposed on the electrode Voltage, then the work will be formed on the surface evenly in a row parallel to the voltage distribution. As shown in Figure 1, when the X in the direction of the electrode on the last imposed a determined voltage, and the Y direction of the electrode without voltage, in parallel to the X-voltage field, contact the Department voltage value in Y + (or Y -) Last Electrode reflected by measuring the Y + on the electrode voltage to the size of the contact will be aware of the X coordinates. By the same token, when the Y added to the electrode voltage to the electrodes X and not on the voltage, by measuring the X + voltage electrodes, the contacts will be aware of the Y coordinates.
2, four-wire resistance touch screen flaws:
Resistance touch screen to the B side is often touch, touch-screen four-resistance of the B side to adopt ITO, we know that, ITO is a thin metal oxide, used in the process, will soon have a small crack, and crack once, The original current flow through the line and forced around the crack, the uniform distribution of the resulting destruction of the voltage, there is a touch screen damage, cracks for the performance of the Department are not allowed to point. With the crack and the increased number of touch-screen will gradually expire, so life is not long four-wire touch screen resistance of the main issues.
3, domestic and imported touch-screen phone is the same as resistive touch screen is, we want to maintain a very easy substitution, as long as the same size touch screen can be a substitution, below the experience of several substitution.
Now many non-brand-name screen handwriting of a high failure rate, we also encountered a lot, and the following to share with you this experience in maintenance,
MTK touch-screen common arrangement
1) 4 line of touch-screen interface for the order of X + Y + X-Y -
2) touch-screen interface 4 line order for the X-Y-X + Y +
3) touch-screen interface 4 line for the order of X + X-Y + Y -
4) Line 4 touch-screen interface for the order of X + Y-X-Y +
5) touch-screen interface 4 line order for the Y + X-X + Y -
6) touch-screen interface 4 line order for the Y-X + X-Y +.
As we meet for regular maintenance of touch screen was a problem, in fact, very simple operating principle that he can be a horizontal Y +, Y-, is a vertical X +, X-in touch screen point of view, can not help but to trouble you The purchase of touch-screen, look at him the same, that is axial to the touch screen, so to connect OK.
4, software-induced failures are also a lot of touch-screen, we can determine how bad is the touch-screen software is bad, my own experience to tell you the following.
Software failures caused by the phenomenon of
Touch-screen software failures are many, there are several characteristics
1) according to the touch screen when the number of health by a 3, 4 by 6 by 7 by 9 or a 9 by 3 or 7, according to a 7 by 3 of 9 This is caused by axial reversed, tested in the touch-screen Inspection of limitations are not allowed to deal with software on OK.
2) The touch screen can not, we go to the four touch-screen measuring voltage, in the case of the net can be detected Y + and Y-voltage 2.8V or two X +, X-voltage, and so on, the touch-screen input and output axial Voltage line proved that touch-screen has not worse, if that is inconsistent with touch-screen does not work, we can deal with the software tested on the following OK.
3) caused by the software lock-axis, can only touch-screen horizontal or vertical can not live Eng vertical line, and so on, settle axial center, is the only touch-screen rather than pressing the center of the digital afterlife is pressed to 5 The other can not deal with software on OK.
5, touch-screen hardware failure caused by the phenomenon of
1) touch-screen is no obvious damage, there is no touch-screen click the reflect, touch-screen measuring voltage is only one of the voltage on the other yo yo 0:00 a few volts, and so on, are generally caused by the touch screen for.
2) touch-screen from time to time in writing or painting intermittent phenomenon occurs when short-term line, bending, alignment, and so on, can not use touch-screen or the lower part of the upper part could not be used, and so on, have a 1.40 touch screen angle can not be used or not, c. And so on with.
3) points in the touch-screen screen from time to time does not reflect the trend, that is not reflected in the menu and so on.
More than a few of my personal experience, so you can quickly determine it is a software failure caused by hardware failure or failures, our maintenance staff is first-line speed is money, speed is a technical difference.
Five-Year Plan, the headset mode detection and repair
1, headset models are basically in a headset interface, or the end of the phone plug failures, is a multi-extract, corrosion, the end of a bad play, bad blocks caused by the headset. We repair the failure of the headset mode, it is necessary to double-check interface circuit, with million will be used to measure voltage switch and headphone Block work, and some MTK chipset design of the conversion circuit and control circuit and so on, CPU Xu Han failure caused by bad or very The small, we often see in the maintenance of software failures, and so on.
2, headphone model is CPU-controlled, CPU-MT6226BA-V1 is the control of foot feet, CPU-V1 is a foot high ban on low-level control, repairs so that we found in the headset mode, the CPU in the foot V1 Voltage 2.8V to add it.
3, headset mode rapid approach
Sent by mobile phone customers that the calls can be silent is to screen a headset symbol on my heart to understand, to open a cell phone to see some amendments, I asked the customers over there, said the amendment did not fix I did not say if the second pick up the phone motherboard, look for one with fine copper wire, copper wire in the degree of tin, with Feng Qiang 6226BA-CPU to the heating, found in a 6226BA-CPU than the CPU to find the foot of the V1 The location of fine copper wire into the power supply to find a 2.8V voltage connect, try booting the machine OK.
Description: In the same maintenance over the phone, do not fix fault is not so good looking, so if you have experienced, then according to your own experience to deal with failure, this is also to save time, save the trouble of checking, it is necessary to quickly and Decisively deal with.
16, the same way memory card and maintenance
1, circuit card is simple, from 4 to send a data clock signal, the main storage is read, when we start the mobile phone in a state of memory card inserted (card control signal into a high-low) cell phone screen Show or SD card has been inserted, such as pull-out tips, we do not often find in the maintenance of identification cards, a lot of failures in the card connector, a variety of memory card blocks, the most closed-end cards is a bad seat.
2, does not recognize card
Customers use the phone that I do not put the MP3, the following can help me, I do not recognize a memory card, open the phone is closed check card Block, SD card in the deck, I also start to identify the cards I check the back seat was found the following card connector has a control switch card, MCINS switch to connect and, when inserted into the card to time, MCINS into a low-level mobile phones have been prompted to insert SD card, and so on, I MCINS Yong Niezai feet and Then the screen showed the SD card has been inserted in the phone when you start out, or insert SD card mobile phone screen is not prompted, insert the SD card when the SD card does not reset the phone system, there will be no SD card inserted, if the shutdown in the boot on the SD card Identified, we should not overlook the maintenance of the SD card switch.
3, does not recognize card
The same is used to open the phone, measuring multimeter card Block 8 of the line-to-ground resistance and found no abnormal, start to do the measurement card 8 voltage line 6 has 2.8V voltage, there is a Grounding, is a clock signal to start in 2-3 seconds when measuring the SD card so the clock has not found foot-voltage voltage, SD card clock in the foot or boot MCINS switch detects when there are SD cards, not detected SD card in the 2-3 seconds from low into high, the clock appeared to be caused by circuit problems! After checking on the Main Board found that while there is a row of resistors and capacitors are dirty black surface, cleaning the following are found in several other countries have corrosion resistance and capacitance, capacitance measurement is one end there are two ends of the earth, the capacitor in the boot removed after the test drive SD card The normal work.
17, circuit camera and maintenance
Camera principle
CPU integrated video camera and processing systems, such as drive, CPU and camera data signals are 8-10 months, the CPU is based on the model itself and the camera set, when the mobile phone into the system to take photographs or video, there is a power of 2.8 V voltage, CPU out of the reset signal so that the camera reset for data transmission at the same time to start working into the camera.
Camera fault maintenance
We often found in maintenance, installation is not ready to spend camera, camera Screen of Death, to take photographs when dark color display screen, photographed in the picture there is time to preserve the image, save pictures and no image is black, non-screen display, such as failure , To introduce the following my own experience in maintenance.
1, the camera itself bad failures
Device is not ready to spend camera, camera Screen of Death, to take photographs when dark color display screen, photographed in the picture there is time to preserve the image, save pictures and no image is a black camera, and so bad in itself caused by failure
2, the device is not ready
Bad software, CPU or bad virtual defend, the camera does not cause the power supply.
Device is not ready when we met a lot of maintenance, we write a new version of the information wrong, that is not camera data will also be installed in place not to drive caused by the camera, the software can also cause bad device is not ready, We usually deal with the case could be a multi-media format, CPU or bad virtual defend also caused many, CPU with 25 lines to the camera, there will be a line break caused by camera failure.
3, ZT288 cell phone, camera does not come out as the screen, the screen is black, but as the picture is normal, I saw very curious, this failure is rare, especially in our maintenance is rare in general do not fault Easily move the Main Board, the maintenance of our instinct, on first look at the following format, or failure, on-line under the months to write the information into the open the boot after the camera images on the screen already had it.
4, the two do not use peer-fault camera phone, I open the board to see all the action again, there is an extract phone, camera, said peers have replaced or failure, so that the camera itself is not the problem , Open the phone to start repair, extract the cell phone in the main board, ultrasound clear that the pre-Taiwan, to look at the camera had no problem connecting Block, to start in the camera when the power supply voltage measurement is also normal, surveying connectivity Block the line of resistance to two found no resistance, is not empty my feet on the main board of the camera block out the traces of corrosion were found on board the black spot is dead, after cleaning by welding back seat The camera installed boot test drive a normal camera. Taiwan has been fixed in the amendment that Taiwan, from ultrasound, drying out after the test cameras installed, this is also normal, not a repair.
Experience: In our maintenance, pay attention to details can not be ignored, he lost, in particular those details to save you time and take up the same phone they are not repair all the big move is basically over, You must do to gain the upper hand on the details of your maintenance to improve the speed, but also to improve your technique.
18, decryption software and processing software
6226BA just in the times listed, we do not have decryption technology, is no way to repair 6226BA phone chips, the beginning of a lot of online users to read out the information on the forum, you can not write the information exchange that is not written into the boot, Information is encrypted, and that many times on the phone to the same body lying there, not a very good way, and so there is only a tool to crack, this time in my dedicated researched the beginning of the decryption technology, did not engage in a few days out Understand that no matter is not filled or emptied into FF address above can not solve the problem of decryption, in a fortuitous opportunity to have a customer used a mobile phone that I often look at the crash was anything wrong, I can open a cell phone is 6226BA The CPU I have a silly, I really 6226BA the CPU is the encryption software can not write, I have to tell customers that your phone is a software problem to deal with software, customers deal with a unified software, I gave the customer-processing software, said there are risks Some cell phone encryption is to write the software will not boot, said that customers do not you write can not write, I ran several of the maintenance shop are saying that there is no way to deal with you on this can be, you write the At this time I said you have to deal with the information needs of mobile phone a few days, the reunification of the customer, so I feel pleased but not show, I can study the following 6226BA encryption issue, because I still have a few phone did not start the 6226BA is also a CPU and his The same, so let the customer on study of the following well here. Customers can use the phone boot, the boot after a crash on the night I put the phone customer information read out by 48 after a month in the online information is not written into the boot, a boot or not, information is really Encrypted so mysterious it, I used a tool to open source data did not look to see what the beginning of a problem discovered by a few to see all the information found in the Department F00000 node. F00000 after I cleared all the information in ten FF is a six-band in the sense of space, in the decimal metric system equal to F, 255, written after the filling into the phone after only a half-day boot, the boot can be
With the normal use of the death is not, this is a new discovery, filled with new information or not boot, is not the original data, there is no decryption code out to understand, just to rest, the operator will be able to fix one, A few days later I found an on-line information and I have not found information on phone model and CPU, the same font type, I put him down in the evening I write this new information has been lying in more than a month of cell phone , The phone did not expect the boot, 6226BA the start of the CPU, I am very surprised I had the original data and information on the following comparison 7M basically the same 7M after a lot of different, I do not like the pre-7M code coverage to the original data Years after the start or not, I also found the following on the Internet have been used to break free from the machine-readable information and I like that I wrote into the boot or not, when I found that I was under the information has been declassified information I previously tried under the new information and contrast the following information is in a section 7M ago and a few other characters do not like no other, I do not like the comparison over a period of the code to cover new information, Written on the cell phone after the boot screen Tang Liang does not reflect the following after the beginning of the ammeter and not the same as the previous 40MA about the current fixed there is some Jishi Miao ammeter to move the following 20MA to 40MA to boot, I have Carefully check the source code to narrow the scope, coverage to the new address information in paragraph 48 after written into the boot of the success of the test machine, start the mobile phone, equipped with card as soon as possible a normal test drive, I was excited, happy night did not break , And two mobile phones, I found a new on-line information, the beginning of the new information not found on this abandoned, and later data also found that the two get.
This is not a story to tell you, this is my cell phone access to decrypt the beginning of the study, since then, their research has been on the phone's data encryption issues to the present, their pay has also brought rich fruit.
Good deposit from SamOnline.
