Basic mobile phone repair tutorial

Section phone repair knowledge
1, fault classification
1, caused the causes of cell phone
(1), the menu settings failure: failure is not, strictly speaking, if no calls are perhaps for the owner to set up call forwarding; play no phone is set up outbound throttling. The baffling problem, first with total reset.
(2), using failure: improper operation generally refers to the user, dislocation caused by adjustment. More common are the following categories:
1), mechanical damage. As the operation or method of application of excessive force is not correct, resulting in mobile devices rupture, deformation, and the module pin loose weld failures and other causes. In addition, flip off axis, the antenna was broken and thrown split casing, water, broken screen, also belong to this type of failure.

2) improper use. When using the phone's keypad keys with the nail tip will cause the keyboard touch bare ground or even fall off; with bad cell phone charger will damage the internal charging circuit; even cause the accident; on the phone menu for illegal operation of certain functionality is turned off, the phone is not working; error led to SIM card password locked, the blind try to create self-locking SIM card protection.
3) improper maintenance. Cell phones are very sophisticated high-tech electronic products, use should be noted that in the dry, the temperature suitable for the use and storage environment.
4), the quality of failure. Some parallel imports of mobile phones is through consolidation, converted, quality underground. Although some phones are digital phones, but does not meet the GSM standard, can not be used.
2, fault classification
(1) does not dismantle the phone only to see its appearance from the mobile phone failure, can be divided into three categories:
1) The first one is not working, including the power supply can not turn connected to the phone and press the power switch without any reaction;
2) The second is not completely boot, press the handset switch current can be detected, but no switch machine normal reminder: if key lighting, display lights all bright, display, character information display with ringer After the start tone adopted by such self-test;
3) The third is to boot, but the failure of some functions, such as the buttons do not show unusual, silent, do not send it.
(2) open the phone, from a few core terms of its failure, also can be divided into three categories:
1) The first part of the supply charge and power failures;
2) The second for the mobile phone software fault;
3) The third part of the fault for the mobile transceiver.
Between the three types of failure was inextricably linked,
For example: impact of mobile phone software, power supply systems, send and receive path phase-locked loop circuit, the transmit power level control, send and receive time-synchronous control channel, and send and receive access to reference crystal oscillator has to provide software for mobile phones running the clock signal.
(To be continued, following more useful!)
Assignment: In the daily maintenance, to understand what factors lead to damage to the role? To understand the damage factors, should we do?
Second, the failure characteristics of common electronic components
Whether the breakdown of natural wear and tear or damage arising from man-made failures, generally attributed to the circuit contacts open, damage to electronic components and software failures of three failures. Contacts open, if it is a broken wire, disconnect the plug aside, poor contact, etc., generally easier to repair them. Damage electronic components, (except obviously burned and fever), often difficult with observers found that in many cases, have to rely on instruments to detect judge, so the maintenance staff, the first essential to understand the various devices effectiveness of the characteristics of this circuit fault for the maintenance, increase maintenance efficiency is extremely important, the following give some common characteristics of effective electronic components.
1, IC
Generally localized damage, such as breakdown, open circuit, short circuit, power amplifier chip easily damaged, prone to software failure memory, and other chips sometimes occur Weld.
2, transistor
Breakdown, open, serious leakage, parameter change bad.
3, diode (rectifier, LED, voltage regulator, variable volume).
Easily be puncture, open to larger forward resistance, reverse resistance becomes smaller.
4, resistance
Under normal circumstances, the resistance of the real efficiency is relatively low. However, the role of resistance in the circuit very important in some circuits, the resistance will change in the static transistor operating point changes, causing the entire unit circuit not working properly. Effectiveness of resistance effects are: loose soldering, resistance becomes larger or smaller, the temperature characteristic variation.
5, capacitor
Divided into two polarized electrolytic capacitors with non-polarized electrolytic capacitors. Electrolytic capacitor's effectiveness features are: short-circuit breakdown, leakage current increases, the capacity is decreased or the circuit. The Promise of the effectiveness of capacitance characteristics are: short circuit or loose soldering breakdown, leakage effects serious or resistance.
6, inductor
Effectiveness characteristics are: break, loose weld.
Above that are all the major components, there are also external components such as quartz crystal FET can not be ignored in the maintenance of the particular vulnerability of the crystal by the vibration and high-power devices (amplifiers, power supply circuit, voltage-controlled oscillator ) problems, there will be no boot or after boot can not access, can not hear other sounds, linked suppliers and other faults.
1, the control of specific experience on the maintenance of books about integrated circuits, transistors, capacitors, resistors, inductors damage characteristics and failure caused by the phenomenon.
3. Troubleshooting steps
Mobile phone no matter what type of fault, must be asked, see, hear, touch, thought, the six stages of repair. But for different models, different faults, different maintenance methods for the six phases of time is different.
1, asked. , As doctor visits, as users must first understand some basic information, such as the cause of the failure process and the reasons for the use of cell phones, etc. age and the situation, such inquiries should be further face police attention and be thought to be clues.
2, see. Wide variety of mobile phones will inevitably encounter a number of their previous contact with the new model or models on the market less to see light of the specific models should be carried out, such as repair your phone, look at the green machine status indication LED lights are flashing, the call to allocate time information display, combined with the observed phenomena levy failure to provide ideas for further diagnosis.
3, listen. Can be repair mobile phone voice quality, volume situation, the sound is intermittent phenomena such as initial assessment levy failure.
4, touch. Mainly for power amplifiers, transistors, integrated circuits and certain components, hand touch can touch the surface temperature of the high and low, such as hot, may wonder whether current or overloading, you can roughly judge the experience base fault location.
5, thinking. The analysis of thinking. Root resist the previous observation, the data collected, used their service experience, combined with the specific principle of the circuit, using the necessary measurements, comprehensive analysis, thinking, and finally to maintenance programs.
6, revised. The components have been invalid for exchange, welding.
For the new phones because of defects in production process, fault movement in the case in many parts of the mechanical stress combined with near, and mostly poor welding parts, Weld and so caused. And fall, squeezing the damaged cell phones have in common fault, break something on the phone can be observed in the case the obvious mechanical damage, in the corresponding part of the movement is the key of the inspected part. The water and power supply caused by mobile phones have in common, water in the phone, if not in time, was oxidized over time, broken
Do not blindly carry out maintenance tests and be demolished power, wind welding components and circuit boards, it is easy to fault did not discharge the old results in new, can be simply restored to the original mobile phone becomes complicated.
1, memories you go in the maintenance of the roundabout, do you think these methods help you repair it?
2, in the maintenance, application of these methods? Please be combined with practical thinking.
Fourth, the general process of mobile phone repair
1, the maintenance process
When receiving the fault plane should be done in accordance with the following procedures:
(1), after first understand hands. Get a machine for repairs, the first not to rush into action, it must first ask fault phenomena, the time and what happened anomalies. Observe the appearance of cell phones, with or without obvious cracks, defects, if there is no flip, antenna folded, the keyboard bald, and can largely determine the machine's fault, other ask what the machine is not water, two mobile phones, have taken place in other No, life is about how much use. For an excellent maintenance technicians, in asking about the process of failure, can largely determine the scope and cough can fault failure of components, so as to efficiently and quickly lay the groundwork for repairs.
(2) After the prosperity of Simple, easy things first.
(3) after the first power machine. To replace the power supply regulated power supply, note the voltage regulated power supply voltage with a multimeter to file to the correction, the source of the output regulator and the battery should be transferred to the same value, 7. 2V, 6V, 4. 8V, 3. 6V or other value. Block with the alligator clip to find the positive and negative battery terminal, together with regulators source, the source of the power supply voltage regulator circuit in series with high-precision multimeter. Look in the boot before the power output is not 0MA, if not, then the cell phone circuit of leakage.
(4) common problem after the first special.
(5) after the first and last class before the class.
(This section to be continued)
Key words: first after the hands-on understanding. After the first simple complicated, easy things first. First power supply, common problem after the machine first, then special. First and last stage, after the former level.
1, memories you go in the maintenance of the roundabout, do you think these methods help you repair it?
6) record failure. Types of faults do not forget to boot, water, falls, no display, dropping more than ten species, but each failure mechanism may occur much difference. Record failure to repair in order to clear objectives, so that between users and maintenance personnel have a certain determination.
(7) records phone models to be repair, IMEI code, MSN code. Every phone IMEI code and the name of MSN codes like mobile phones, so that the error does not occur when the handover.
(8) control the operation method of mobile phone for repairs. Repair cell phones do not use the phone, as the same as repairing a car will not drive a car, and some maintenance personnel on the operation of mobile phones is very vague on change ringing, changing vibrations, automatic timing, the last ten phone numbers display, call forwarding, check IMEI code, telephone directory function, the machine's display and modification of years on very strange, do not even know the meaning of phone status indicators: traffic lights that flash alternately calls, the service area flashing red light, green light flash within the scope of services. Operation can be adjusted out of the menu functions, it is impossible from the hardware maintenance solutions.
(9) did not fully grasp, do not repair phones when the user's face. Observed up to only disassemble in order to prevent tension caused by operator error.
1, write a daily diary maintenance.
(10) carefully observe the circuit board. The failure observed with the eyes no longer detected by other means, such as integrated circuits work, should not result in a high temperature, if the hand does it feel hot, we can determine the initial internal short circuit phenomenon, word by direct observation, you can find some fault clues. However, direct determination, is built on the basis of past experience, not some maintenance experience, are not effective.
(11) plus electricity. In the above inspection, the boot power up to hit the amp output voltage regulator source file to see the power of the output is not the appropriate number of standby current, if not, then there must be trouble. Can check amplifier, leakage, software.
(12) to check the power path.
(13) check to receive access.
(14) to check input and output port, SIM card, ringing, keyboards, displays and other pathways.
(15) Charles emission pathway.
(16) points with a heat gun repair welding Weld.
(17) in the correct order of removal. Repairs, often to disassemble. In disassemble, should clarify its structure and location of components and accessories. Disassemble all the time clear screw fittings to connect position, when installed does not appear in the final dislocation.
(18) record maintenance log.
The daily maintenance log as is the doctor's case histories, what a day closing machinery, machinery for how long, check the phenomenon of what, how repair, whether repaired, have recorded. Do not repaired excited, think about how to solve the problem of taking those bends: no fix and do not be discouraged, analyze why there is no fix is found no cause of the malfunction? Can not be resolved or what? Later faced with this problem how do? This is a good way to improve self-learning.