Repairing For Signal Problem

Repairing For Signal Problem

We are going to discuss here some techniques and steps to repair no signal condition in mobile phones irrespective of brands

Here we are doing some critical study of the components which are mostly responsible in mobile phone no signal or low signal fault. first of all I am going to advise you about some steps to be taken while cheking and repairing no signal condition in mobil phones.

-always remove phone covers slightly because some phones like sonyericson k500i has sticker type antenna and could be damaged while removing phone cover or disassembling mobile phone .

-avoid touching antenna and antenna pad with hands or dirty tweezers if it is done so you can clean these contacts with CTC (corbon tetra cloride)

-do not over heat components near antenna section.

How to repair Signal problem?

Here we are discussing the techniques to repair signal faults in mobile phone first of all we are discussing about no signal condition

Common reasons of No signal:

-antenna is not connected to phone either contacts or tracks are open

-antenna switch is not switching for rf signals

-some mutual copler may be damaged

-rf filters may be damaged

-rf signal processor is not working

-rf signal generator (VCO) is not working

-software problem

steps to be taken:

1.check if antenna is properly conected to antenna pad if not then you can clean it and adjust it with pad if it is not possible then some technicians use jumper to connect antenna with antenna pad. in condition of open track between antenna switch or diplexer and antenna you can check continuty between antenna and antenna pin of antenna swicth, if track is broken you can make a jumper at this place to fix this problem.

2.most often you may come to know that in signal problems there are lot of sets which have faulty antenna switch. so you can check it by removing antenna swith and makeing a jumper between rx tx and antenna pin see example below.

1.it is very rare that you may come to know that the phone you are repairing hase damaged mutual coupler you can just check mutual by checking continuty betwee four pins in one side and ofour pins in the other side but it is very rare tofind a damaged mutual coupler but the chances still exist.

2.rf filters a also very rare to find in no signal problem in mobil phones but you can't ignore this because in nokia 8210 there were mostly found damaged filters in signal faults.

3.Rf signal processor is the main component which controls the whole Rf section if the above steps fail to power on signals in mobile phones then you can consider Rf signal processor reponsible for that fault, first you shoult know that in nokia sonyericsonyou can find rf signal processros in the form of BGA IC (which has terminals below its body) but in samsung it is mostly in the form of SMT IC ( which has its terminals at the four sides of its body) remeber some time BGA ICs are suffered of dry soldering so if you find you rf signal processor in BGA form you can first check it by making rehot it and if the problem exists you can replace this IC. note ICs and IC type components has no verified checking methode. so you can take a chance to replace this IC if you found problem after taking the steps mentioned above.

4.In some mobile phones rf signal generators is used to produce a signal which is often mixed with rx recieved from antenna and then there is some processing on the mixed form of rf signal so if rf signal generators which are mostly known as VCO (voltage controlled ocilator) is corrupt no signal faults may occure.

5.In the final I am going to tell you about the software function used in mobile phones your mobile phone uses its software to connect to the network and to set frequencies in mobile phones and there are some instructions found about controlling the hardware rf section by CPU with the help of software, so if the software of your mobile phone is corrupted then you may have signal faults in your mobile phone. you can see the example of all nokia DCT3 models if there is no "set faid" option is checked while flashing mobile phone the phone after flashing does not show signals so dont ignore software problems in no signal.

When signal comes and then disappears.

if you find a problem in some mobile phones that when mobile phone is turned on it shows signals for a while and then signal disappears after some seconds you can consider your Rf power amplifire is faulty or unsoldered or dry soldered.

explanation

when we turn on the phone it shows the signal strenght bars because it is recieving signals from the base station and then our phone tries to send its information about its seriel number and SIM identification number to the base station and you can think that whenver phone tries to send signals to the other device it uses Rf Power amplifire (PA) and if the PA is not supporting the phone to send the informations to the base station then our phone disconnects its half way link to base station and stops displaying signals.

how to repair this problem?

1.first check the supply connection with your PA if supply is broken then you can make a jumper at this point

2.check Tx signal tracks comming to the PA from rf signal processor if broken then jumper it

3.check Tx signal tracks going from PA to antenna switch if broken then jumper it.

3.rehot your PA.

4.remove PA and then place two jumpers in rf in and out points at the

5.place of PA

6.replace PA it will be 100% right in working now.