Samsung SCH-2000 Service Manual

Also see for SCH-2000: User guide

Circuit Description4-6 Samsung Electronics4-4 Hands-Free KitHands-free board is largely composed of caradapter circuit and Hands-free circuit.4-4-1 Car Adapter CircuitPOWER SUPPLYInput power switching circuit : This circuit (Q902,Q903) is power switching control circuit. It supplypower for hands-free kit.8V regulator (U806) : This circuit supplied powerfor audio amplifier (+8V).Vcc regulator (U807) : This circuit regulate Vcc(+5V).CHARGER CIRCUITThis circuit charges battery pack by detecting thetemperature of battery, the slope of temperature,the slope of the voltage of battery, charging time,etc.During charging time turns on red LED. Chargingis completed, turn on green LED.Voltage detection circuit : Charging circuit isdesigned to stop charging when the chargingcircuit is decrease.The voltage of battery is entered to A/D converterlocated in U701 #4. (B/VTG)Temperature detection circuit : The temperatureof battery is measured by missing NTC thermistor.NTC thermistor has a characteristics of Log-scale.It can obtain a linear characteristics by the parallelconnection of resistors.4-4-2 Hands-free CircuitPOWER SUPPLY (U808)U808 regulated -5V.TX PATHThe audio signal from external Mic(J701) flowsinto U802 #11. U802 include amplifier and Controlcircuit for hands-free operating. U801A amplifiedinput signal. Output signal transmit to HHP.RX PATHInput audio signal canceled noise by differenceamplifier (U801c). U802 process hands-free action.The RX audio signal is input (U805). The speakerdrive amp (U804) amplify the Rx audio signal andthe output of U804 is go out of speaker.Battery Type Capacity Charge Time Charge CurrentStandard 1000mAH about 3h °æ30M OA ~ 900mAExtended 1600mAH about 5h °æ30M OA ~ 900mA