Check the antenna connector and antenna components, make sure the well connected. Especially if your phone is a phone with internal antenna, associated with the PCB mainboard via a pointer or two elastic contact, if both pointers this contact has a bad contact, a problem that arises is the lack of a network (no network) and a bad signal reception even missing signal (no signal). Especially with the engine knocking or falling into the water, the contact is bad and of oxidation will occur at the contact pointer. The antenna switch is the only way to rnenerima and send a signal, if damaged or soldering the pins are wrong, no problems will arise or the transmission network
Next we tried to find the network on the phone with manual methods, if this method fails in this manual to find the network, so that we can be sure there is a problem in RF IC (HAGAR), change the RF IC (HAGAR), then the problem will be completed
Network can be searched by manual methods but sometimes fail, can not even connect to the network. This phenomenon is caused by problems with RF IC (HAGAR), AUDIO IC (COBBA). If the module COBBA revealed the presence of errors, possibly caused by his unit and BGA soldering around the poor, or lack of flow, whereas most of the problems caused HAGAR bad units
If looking for a network with the manual method we only get one phone (one) operator / mobile service providers only, then there is a problem with IC VCO, replace the VCO IC was then the problem will be completed
If there is no problem with the manual method, check the flow path from the battery to PA IC, if there is no problem with the next point we check whether the IC component of the PA to function properly. We can use to test the IC multitester PA, PA IC, if it does not work properly, we replace the problem will be completed IC PA
After testing and we do repairs on hardware but still no signal / lost, then we moved on software. We flash your phone in accordance with the type of phone and software versions or previous mobile phone with a newer software version (upgrade)
