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Not boot failure is a common fault of the phone, it can be seen from the above analysis , causing no boot variety of reasons, such as power line circuit , power supply IC Weld, damaged, no 13MHz clock , the logic circuit is not working properly , software failures and so on. General repair method is: use an external power supply to the phone , press the power button or using veneer boot method ( for Motorola phones powered tailstock can be directly plugged to socket ) , observe the ammeter for change , if the change ammeter pointer to determine the scope of failure , combined with maintenance points described previously excluded. Here a few minutes to analyze several situations .
1 meter pointer does not move
Press the power button ammeter pointer does not move, the phone can not boot. This phenomenon is mainly caused by power supply IC does not work . Focus overhaul overhaul following:
( 1) The supply voltage is normal ;
( 2 ) to the positive power supply circuit work if there is the phenomenon of C ;
(3) whether the power IC soldered or damaged ;
( 4 ) whether the power line circuit breaker .
(2) 20 - Current 50mA or so , then back to zero
Press the power button 20 - Current 50mA or so , then back to zero , the phone can not boot. There are about 20 ~ 50mA current , the power part of the normal. You can find the following aspects overhaul .
( 1 ) Power IC with output, but the leakage or Weld, resulting in not working properly ;
(2) 13MHz clock circuit failure ;
(3) CPUT as not normal ;
( 4 ) version of the register is not working properly .
In actual maintenance to power IC, CPU, version , register Weld , 13MHz ( or 26MHz, 19.5M ~) crystal, VCO no working power in the majority.
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