troubleshooting mobile phone faults part1

8/8/2019 Troubleshooting Mobile Phone Faults Part1

http://slidepdf.com/reader/full/troubleshooting-mobile-phone-faults-part1 1/5

Troubleshooting Mobile Phone Faults

Troubleshooting:

Methods of search of malfunctions. Repair includes the works connected with

replacement of components, repair of units, blocks, details, elimination of shortcircuits, restoration and adjustment of the device. Search of malfunctions ± themost labour-consuming operation of repair also demands good knowledge, skills

and skill.

The technology of repair develops of four stages: revealings of malfunction,

definition of its character, elimination of malfunction, check after repair. To findmalfunction ± means, to find the given up, failed element, unit, the module, the

block, the cascade. All can be divided malfunctions on mechanical and electric.

Ways of searching malfunctions:

1.External survey allows to reveal the majority of mechanical malfunctions,together with some electric. External survey it is possible to check up quality of assembly and installation. At quality check of assembly manually check mechanicalfastening separate units. External survey check also quality of electric installation:

reveal integrity of connecting conductors, absence ??????? solder which can lead toshort circuits between separate sites of the scheme, find out wires with the brokenisolation, check quality of soldering, and also presence of all elements according tothe scheme. External survey supervise conformity of face values of components,reveal defects of separate elements (breakage of conclusions, surfaces of resistors,mechanical damages of ceramic condensers, etc.). External survey make, as a rule,at the disconnected feed. Thus it is necessary to watch, that in installation casual

subjects which at inclusion of the device can cause short circuit have not got.External survey it is possible to reveal malfunction of variable resistors (onsmoothness of a course of an axis), tuning condensers, etc. In the includedcondition it is possible to define an overheat of transformers, ?????????????????condensers, cases of transistors and ??. Smells can testify To presence of malfunctions in the scheme of the device from an overheat of components, changeof tone of the sound fluctuations caused by work of units of the scheme which areabsolutely not audible during work or have characteristic tone of sounding.Sometimes during external survey there are doubts in serviceability of components.In that case it is necessary ??????? an element and to check up its serviceability

more carefully.

2. The way of intermediate measurements consists in consecutive check of passageof a signal from the block to the block (from the cascade to the cascade) beforedetection of a faulty site. The given way is applied, for example, in the amplifier,consisting of several cascades when on an output of the amplifier owing tomalfunction in any cascade there is no signal. For revealing this cascade on aninput of the amplifier from the generator submit a verifying signal and anoscillograph look through oscillograms on outputs of separate cascades. On an

output faulty the signal is absent.



3. The way of exception consists in consecutive exception of serviceable cascades,units and blocks during search of malfunctions. So, if in a radio receiver there is nosound signal on an output malfunction can be as in high-frequency, and low-frequency parts. If to submit on an input of the amplifier of sound frequency averifying signal and thus on an output the signal the amplifier is serviceable will beaudible, it can be excluded from the further troubleshooting and to pass to check of a high-frequency part of the receiver.

4. Way of replacement of separate faulty elements, units or blocks on serviceablewidely use at check and repair. For example, having replaced the block, the module

on obviously serviceable, it is possible to be convinced of malfunction replaced.

5. The way of comparison consists in comparison of parameters of the faulty devicewith parameters of serviceable same type or mark.

Troubleshooting carry out by the certain rule (algorithm) allowing as much as

possible to reduce time of search.

Element base 1

Resistors are the most widespread elements of the radio-electronic equipment.Constant resistors provide operating modes of intensifying devices, allow to

extinguish surplus of a feeding pressure, a part of smoothing filters, are used individers of a pressure and as equivalent loadings. Variable resistors use inregulators of various sizes, tuning apply to installation of operating modes of theequipment during adjustment and adjustment. It is possible to carry breakage of conclusions to malfunctions of resistors; change of resistance; an overheat ortransformation into coal a spending layer; breakdown of the resistor (infringement

of an isolating covering) at excess of an admissible pressure; infringement of smoothness of a course and contact (in variable resistors); bad fixing of value of resistance (in tuning resistors). Malfunctions of resistors can be revealed visually orby means of an ohmmeter. It is necessary to replace the faulty resistor. The specialattention should be given capacities of dispersion of resistors. It is supposed toestablish the resistor with greater capacity, but not on the contrary. At work in apulse mode average capacity should not exceed nominal since through the resistorperiodic impulses of a current which instant values can exceed considerably valuesin a continuous mode proceed.

Element base 2

Condensers are a part of oscillatory circuits, strip filters, are used as dividing andblocking, elements of communication, stores of electric charges, in smoothingfilters, for temperature indemnification, for suppression of a radio noise, etc. Toprincipal causes of failures of condensers of constant capacity it is possible to carrymechanical damages; breakage of conclusions; breakdown insulator; change of capacity; increase of losses; change of an insulance. Tuning and variablecondensers can have such failures: short circuit between facings; bad fixing of value of capacity at its installation; mechanical damages. Failures of condensers



can be revealed by visual inspection and probing devices. The elementary failuresdefine by means of an ohmmeter. Features of application of condensers: ± At workwith high-voltage condensers it is necessary to consider the phenomenon of absorption of electric charges in insulator, (from 3 up to 5 %) at the fast categoryof the condenser on loading ± it is dangerous energy causing incomplete kickbackto a life. ± at some mica and ceramic condensers ³blinking´ ± spontaneousspasmodic change of capacity can take place. ± at electrolyte condensers significantdrop of resistance of escape leads to infringement of a mode of behavior of transistors and microcircuits. Complexity of detection of the depressed resistance of escape consists that it can be shown energized at the working device. ± drop of capacity of condensers in smoothing filters leads to increase in pulsations of thestraightened pressure. ± at a choice electrolyte the condenser except for nominalcapacity, it is necessary to consider an operating voltage, the current of escapeshould not exceed 0.1 mA on 1 mF. Submission of a pressure of return polarity is

inadmissible.

Element base 3

Switching products are intended for necessary switchings in electric circuits of aradio set (switches, switches, the relay, plug sockets, pads, etc.). The reasons of failures of switching products can be mechanical damages of contact pieces,pollution of electric contacts, failure of mechanical devices (the springs, separatedetails), a voltage failure of an insulation substance of the switch, short circuitbetween contact groups, jamming of mechanical parts as a result of their

deterioration. To define failures it is possible visually or an ohmmeter.

Element base 4

Diodes apply to straightening alternate currents, detecting of the modulatedfluctuations, restriction of amplitudes of signals, maintenance of temperatureindemnification of position of a working point (mode of behavior) of transistors, foran outcome in logic circuits. Failures of semiconductor of diodes can be revealedvisually or by means of an ohmmeter. At check by an ohmmeter in direct inclusionresistance of transition should be less than tens Ohm, at return inclusion ± morethan hundred Ohm.

Element base 5

Stabilitrons are intended for stabilization of a pressure. As a matter of fact it is thesemiconductor diode, the pressure on which in the field of a voltage failure atreturn offset poorly depends on a current in the set range. The control of stabilitrons displaced in a forward direction is carried out by check of resistance, aswell as at diodes. At the control of stabilitrons without not dismantled the pressurebetween the anode and the cathode which should be equal to a pressure of stabilization of a stabilitron is measured. If the pressure is equal to zero thestabilitron short circuit (is punched) if the pressure is much more, than a pressure

of stabilization in a stabilitron there is a breakage.



Element base 6

Transistors are active (intensifying) devices. Detectings, generating,transformations of electric signals are used for strengthening, and also forrestriction of amplitudes and in schemes of switching, etc. the Reasons of failures of transistors can be breakages of conclusions; interelectrode short circuits; anoverheat and collapse of transitions; increase of a return current of transition;mechanical damages (cracking and deformation of the case). Failures define bymeans of probing devices ± testers or special devices for measurement of

parameters.

Element base 7

Integrated microcircuits are very widely used in cellular telephones. They representthe microelectronic devices containing diodes, transistors, resistors and carrying outthe certain function (for example, the booster of capacity of sound frequency). Atoperation of microcircuits it is necessary to observe strictly polarity of feeding

pressure. The reasons of their failure can be breakages of conclusions;interelectrode short circuits; an overheat and collapse of transitions; mechanicaldamages (cracking and deformation of the case, hit of a flux between conclusionsand the case of the integrated microcircuit, leading gradual refusals, etc.) . Atsearch of failure in the beginning supervise a mode of behavior of an integratedmicrocircuit on a direct current. The underestimated pressure on one of conclusionsof an integrated microcircuit can be because of presence of escape of the condenserconnected to this point which at check can be disconnected. Working capacity of anintegrated microcircuit can be checked up and in a dynamic mode, by means of anoscillograph, supervising passage of the signals generated and brought on itsinputs. At check of an integrated microcircuit it is necessary to be convinced, that

its output is not shunted by the subsequent cascade. For this purpose it is possibleto cut a printed path.

Common Faults In Mobile Phones:

First of all we will discuss how many main functions a mobile phone often has

irrespectively of mobile brands.

A typical mobile phone has various types of faults which can be distributed in two

main kinds of faults:

Hardware faultsSoftware faultsSetting Faults

Hardware Faults:

Hardware faults in mobile phones are related to mother boards of mobile phone,batteries and any physical fault will be amount to hardware faults. I have pointedout as much hardware faults as much i remeber this time but if you have a fault



which is not listed below you can tell me by clicking here I willo be glad to knowthat it would be a great help for me too.The list of common hardware faults is givenbelow.

* dead set condition* no charging* battery empty* auto charging* low signal* No signal* voice problem* vibrator problem* ringer problem* backlight problem* auto turn off * hanging problem* insert sim (no sim card inserted shows on the screen)

* keypad problem* display problem* Software faults* no signal* dead set* display* contact service (contact retailer, contact service provider)* Test mode* not charging

* Setting problem:* call divert

* sim lock* security code* country lock* cnfiguration of SMS* configuration of GPRS

* configuration of call

troubleshooting mobile phone faults part1

Documents