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1、打印机主板维修（Printermotherboardmaintenance）First,thebootlineisnotnormal,causedbynotbootUndernormalcircumstances,pressthepowerbutton,thepowerbuttontriggervoltageshouldbechanged,ifnochangeisgenerallythepowerbuttonisbadorbootlinebroken,weld,damagedcomponents.Mai
2、ntenance,withexternalpowersupply,observethechangesintheammeter,iftheammeterdoesnotrespond,usuallythebootlinebrokenorthebootkeyisnotgood.Two,batterypowersupplycircuitcausedbybadbootFormostmobilephones,themobilephoneplusbatteriesorexternalpowersupply,thesu
3、pplyvoltagedirectlytothepowerworkerC,ifthesupplyvoltageisnotaddedtothepowerIC,thephonecannotboot.ForMotorolaphones(otherthanMotorolaT2688),powersuppliesvary.BatterypoweredandexternalpowersuppliesareswitchedviaelectronicswitchestopowerIC.Thatistosay,there
4、aretwopathstothepowersupplyofthemobilephone,oneisbatterypowered,andtheotheristheexternalinterfacepowersupply.Whentwochannelsofpowersupplyatthesametime,theexternalinterfacepowersupplypriority.Theswitchingofthetwopowersuppliesiscontrolledbyanelectronicswit
5、chtube,andtheutilitymodelmainlyachievestheprotectionofthecurrentofthewholemachine,andpreventstheintegratedcircuitofthemobilephonefrombeingdamagedbecauseofshortcircuitorleakage.However,iftheelectronicswitchisdamaged,thesourcemodulemaynotgetthebatterypower
6、supplyvoltage,causingthephonetonotboot.Forthistypeofmobilephonepoweredbyanelectronicswitch,itcanbepoweredbyanexternalpowerinterfaceaswellasbyanexternalpowersourceviaabatterycontact.Thepowersupplycanbesuppliedbydifferentpowersupplyduringmaintenancesoastod
7、istinguishthefaultrangeanddeterminewhethertheelectronicswitchisnormalornot.Ingeneral,ifthepowersupplycircuitisbad,pressthebootbutton,theammeterwillnotrespond,andthisisverysimilartothepoorbootline.Three,powerICcausedbyabnormalbootThemobilephoneshouldworkn
8、ormally,andthepowercircuitshouldoutputthenormalvoltagetotheloadcircuit.Inapowersupplycircuit,powersupplycircuitICisitscore,differentvarietiesandtypesofmobilephone,powersupplymodeisalsodifferent,somepowersupplypowersupplyci
