The antenna type of phone is high gain omnidirectional antenna

The antenna type of phone is high gain omnidirectional antenna. 
The quality of mobile phone batteries on the market today is very different when the symptom is related with the battery (such as: working hours or standby time was significantly shorter), the Act can be used to determine the point of failure is a part of the battery in the circuit . The specific method is: first battery is fully charged, then the batteries on a false load power supply current is controlled at about 300mA, time for about 5 minutes. If the battery is normal, then the terminal voltage should not drop. More rigorous methods to measure the capacity of the battery, but more time-consuming. Note: According to the nominal voltage of the battery, the dummy load is available 3V, 4.5V, 6V bulb or external series resistance of a power. Measurement line connected to the battery reed only by mechanical crimping and not welded, so as not to damage the battery or accident. phone should be installed in the proper way.
The law is a kind of emergency in the home appliance repair. Its precondition is not a major impact on the whole electrical indicators, and not endanger the safety of equipment (such as: switching power supply jumpers maintenance). For the maintenance of mobile phones, available thin high strength enameled wire (Φ0.1) jumper 0Ω resistor or a unit, with the 100pF capacitor connected across RF or IFSAW filter. Most GSM mobile phone with a certain degree of self-test and fault diagnosis function, which is helpful for rapid fault location to a particular unit. In using the law to require that the phone starts up normally, but the maintenance must also know how to enter the diagnostic mode. The latter requirement requires maintenance at hand detailed maintenance information related to mobile phone. phone should be protected well. 
(No signal) for the mobile phone is not network failures can be divided into no reception and no emission either situation. Receive: (to see whether the search current general search current jumping back and forth between 5 ~ 20mA signal for about one second swing time). Search current network: failure in the receiver front-end circuit (such as antenna switch, receive filters, and one, the second IF filter), the general components Weld or damage. Search current and the current 100-150mA constant beating, such a failure occurred in the VCO is not normal and 13 trillion AFC is not normal, should focus on examination of these two parts and with whom connected circuit. The good phone company has the complete testing equipment of good quality.
No search current network: failure in the logic part, typically CPU-free output of the RX-ON signal, the RX-audio IC I / Q output of the chip, the CPU soldered or not of the software, data, power supply IC (power supply pipe ) to the receiver circuitry. Search current is too large (more than 200mA); failure usually occurs in the intermediate frequency IC and connected components, check the IF IC whether the Weld or damage.