Kenwood TH-D72A Service Manual

Also see for TH-D72A: Instruction manual User manual Instruction manual Instruction manual Instruction manual

Contents

TH-D72A/D72E118. Control System8-1. RESET, BACKUP circuitWhen the supplied +B voltage falls, and the 33M voltageis detected to be lower than the threshold voltage of theRESET IC (IC726), the connected Main MCU (IC737) detectsthis with the interrupt terminal (/RST), backs up the data tothe EEPROM ICs (IC730,IC731), and turns off the power.8-2. LCD, LED, KEY circuitThe LCD Display is controlled by the driver built into theMain MCU (IC737). The contrast is adjusted by the regulatorIC (IC701), similarly controlled by the LCDCNT signal fromthe Main MCU (IC737).On the other hand, the LEDs (D710~715, D718~724) forthe LCD and 16 KEY backlight are lit by the LAMP B powersupply through the DC switches (Q721, Q722). The port ofthe Main MCU (IC737) corresponding to the 16 KEY is com-posed of a 5x5 matrix and detects a pressed KEY by scan-ning in the software.8-3. INT-GPS controlThe GPS unit installed in the equipment communicatesdirectly with the Main MCU (IC737) and is controlled. The in-ternal GPS power supply changes with the DC switch (Q701)controlled by the Main MCU (IC737).8-4. RTC functionThe RTC IC (IC717) that operates with the lithium batteryhas a clock function.8-5. PC portIt corresponds to the connection to the external instru-ment (PC) through the USB connector.8-6. COM portTo correspond to the connection with the external GPSequipment, it communicates by switching ICs (IC708,IC709) by the Main MCU (IC737) / TNC MCU (IC727) andthe RS232C driver IC (IC702).Figure 7 Control circuitIC702RS232CdriverJ702 TXDRXDCOMportSW ICIC709USBdriverIC710V contIC701IC703RESETICIC726RTC ICIC717 X701EEPROMIC730,IC731RegulatorICVbusSWSW ICIC708232B_SSKY_SWRXD_COMTXD_COMTXD_EGPSRXD_EGPSDCSW DCSWQ70433CJ703PCportIC736Vbus_USBLAMPLCDLCDDCSWDCSWQ722Q721LAMP BBacklightLED/RSTRXD_IGPSTXD_IGPSGP_ONGP_PSVGPS Q70133CINT_GPS33MIC737MainMCUTNCMCUIC727CIRCUIT DESCRIPTION