Kenwood 144MHz FM TRANSCEIVER K2E Service Manual

TH-K2AT/K2E/K2ET10Power Supply Circuit■ Charging CircuitWhen an external power supply is connected to the DC INterminal, the constant-current circuit consisting of Q33 andD31 provides a constant current of approx. 110 mA to the Ni-MH battery.If no external power supply is connected to the DC INterminal, the constant-current circuit does not function.■ Power Supply Switching CircuitThe voltage supplied through the battery terminal or DC INterminal is branched in the power supply switching circuit asshown in Fig.10 and then supplied to the required components.■ Battery Type Recognition CircuitWhen the battery pack is attached to the transceiver, thebattery type is recognized with the T terminal on thetransceiver. This battery type recognition activates chargingfor the Ni-MH battery pack and displaying the battery meter.+-TBJ2RN2701XC6202PB52FRQ41D32D805T SWQ37, Q382SK18305MCHARGESWRB051L-40IC6D48,49D42,43,46D47,44BATTCHARGE5R SWTK11250CUCB5.0VTK11250CMAVR5C SWPROTECTCPH33172SJ347Q35CHARGEBTDETQ34Q57 D33IC12AVR2SB1184(Q,R)2SC4617(R)IC45MS SWQ555MV SWQ36RB521S-30DC-INDETRN2105AF AMP2SB1184(Q,R)PROTECT5.0V11.5VAF/LAMPAVRRN2105Q53PROTECTTHERMDET2SK1830BRB051L-40Q33AVRIC9BPROTECTD36RB521S-30D35PROTECTRB521S-30PROTECTD30RB521S-30IC8MPUD31DA221CONSTANTCURRENTBTEMPDCDETBATT TERMINAL7.5V Norminal(6.0 - 9.0V)DC IN13.8V Norminal(12.0 - 16.0V)IC1TCXOQ4,5,6D40,415R5TVR1ENC5CQ9,10,13D8,10TH1IC16Q475MVIC3,17D9,14Q16,17Q22,23,24Q59IC5Q305MSFig. 10 Charging and Power supply switching circuitControl System■ Reset and Backup CircuitWhen power is supplied to the transceiver, the 5M voltagegoes “H” as C303 is charged.A rising edge of the 5M voltage is detected by the voltagedetection IC (IC11) and when its output (RESET) goes “H”,the reset status of the MPU is released.D35 R244 5M5CC307R243L63BATT 5VAVRIC9IC8MPUIC15EEPROMTiming chartPowerON5V5M0PowerOFFIN OUTC303+IC11IN OUTRESETIC10IN OUT INT5VRESET05VINT0If the supplied voltage to the transceiver is reduced andthe 5M voltage falls below the detection voltage of the voltagedetection IC (IC10), the MPU detects it by an interruptprocessing, backs up data in EEPROM (IC15) and turns thepower off.Fig. 11 Reset and Backup circuitCIRCUIT DESCRIPTION