3 . Careful observation battery and battery contacts between the spring contacts are loose , spring contacts are dirty, these phenomena could easily lead to phone does not boot, sometimes power outages and other malfunctions.

4 Carefully observe the information on the phone screen , watching the signal strength values ​​are normal , the battery is sufficient , if the display is intact. Understand the entire phone receiver, transmitter , performance logic and other parts .

5 No phone screen indicates the signal strength display inspection card failure , to use a good mobile phone SIM card inserted , if the phone can work normally , indicating a malfunction caused by bad SIM card , if the phone 's fault can not be ruled out , there is a fault on the phone circuits.

6 required to connect test instruments, test instruments , and open the correct settings , determine the initial phone fault type and fault coverage . Printed circuit board inside the phone , are inlaid with different skill levels and grades of CMOS chips , as well as the new components , and therefore do not carry out maintenance operations in the strong magnetic field of high voltage , high current order against impact damage. Maintenance operations , the need to work in an anti-static bench , instrumentation and maintenance personnel , the table should be well grounded electrostatic shield to prevent static electricity.

7 workbench to keep rooms clean, sanitary , full maintenance tools , and handy . Maintenance operations , according to a certain order before and after handling, pick and place chips, components must discharge certain order , so as not to confuse . Clean the board, independent of the operation , to prevent all of the solder , solder balls , wire material, conductive material falling into the circuit board to avoid failures in other areas .

8 different manufacturers , different models , different styles, its version number is different , the use of qualified normal version of the same chip , components, avoiding the replacement of different versions of the chip . Refrain from using substandard , piracy, smuggling chips , components, so as to avoid more complex faults. In this case, the correct analysis of the circuit , correct an error of judgment . Failure to find the right parts is important to avoid false positives.

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