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GSM mobile phone belongs to a class of communication appliances , it is conceivable that it 's maintenance practices in many ways with other household appliances have common characteristics, but because of the complexity and the use of SMT ( Surface placement process ) the particularity of mobile phone software also makes mobile phone repair has its own characteristics. In the mobile phone repair There are several methods used .Btjservice manual download site
First, the welding method
Compared with other household appliances, mobile phones circuit solder joint area is much smaller , and therefore , able to withstand the mechanical stress is very small , very prone to failure Weld , and as such , many mobile phone repair personnel are relying on a hot air gun " conquer the world " and started , showing the significance welding method in the mobile phone repair . The so-called welding method, which is possible in the unit , and then by using the principle of analysis to determine fault in a large area of the unit , " welding and cleaning. That is relevant to the welding points are questionable welding again. Welding tools available anti-static hot air gun and soldering iron tip .
Second, the voltage method
When we repair household appliances, are aware of the importance of voltage method , repair phone is no exception, after power voltage test circuit through several key points , you can quickly determine the scope of the fault and the fault point . This method is simple , convenient , just a multimeter can. Voltage tests include the following aspects:
1 power supply output voltage is normal. Phones generally use a dedicated power supply voltage generated by the chip machine , including the portion of the radio part , logical / audio portion , the two groups supply circuit redistribution . If the Motorola V998 mobile phone, power chip (U900) to work properly, the voltage will produce the following groups : from U900 G9 end of the internal reference voltage stabilization device (VREFREG) VREF output voltage of 2.75V , the voltage sent to the IF module U913 ensure IF module operates in a steady state ; from U900 B5 end of the internal voltage regulator V3 (V3REG) output voltage of 1.8V , to the central processor U700; internal U900 from J5 end of the V2 voltage regulator (V2 REG ) V2 output voltage of 2.75V to all logic modules provide a CMOS operating voltage of 2.75V ; A6 from the end of the internal U900 V1 voltage regulator (V1 REG) 5V output voltage Vl to the digital signal control circuit , the negative pressure IF circuits and power supply module ; from U900 C6 end of the internal SIM regulator (VSIM-REG) output VSIMl 3V or 5V supply voltage of . If the voltage is not normal more than a few will make the corresponding circuit is not working properly , can also cause serious turn .
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