Kenwood TK-7180H Service Manual

Also see for TK-7180(H): Brochure & specs Specification Instruction manual Brochure & specs Instruction manual

Contents

TK-7180H/7182H214. PLL Frequency SynthesizerThe frequency synthesizer consists of the TCXO (X301),VCO, PLL IC (IC301) and buffer amplifiers.The TCXO generates 16.8MHz. The frequency stability is2.5ppm within the temperature range of –30 to +60°C. Thefrequency tuning and modulation of the TCXO are done toapply a voltage to pin 1 of the TCXO. The output of the TCXOis applied to pin 8 of the PLL IC.The VCO consists of 2VCO and covers a dual range of180.85~218.85MHz and 136~174MHz. The VCO generates180.85~218.85MHz for providing to the first local signal inreceive. The operating frequency is generated by Q307 intransmit mode and Q306 in receive mode. The oscillator fre-quency is controlled by applying the VCO control voltage, ob-tained from the phase comparator (IC301) to the variable ca-pacitor diodes (D306, D308, D310 and D311 in transmitmode and D307, D309, D312 and D313 in receive mode).The T/R pin of IC404 goes “high” in receive mode causingQ307 and Q309 to turn off, and Q306, Q308 and Q310 turnon. The T/R pin goes “low” in transmit mode.The outputs from Q306 and Q307 are amplified by bufferamplifier (Q311) and doubled by Q301 and then sent to PLLIC.The PLL IC consists of a prescaler, reference divider,phase comparator, charge pump (The frequency step of thePLL circuit is 10, 12.5 or 15kHz). The input signal from thepins 8 and 5 of the PLL IC is divided down to the 10, 12.5 or15kHz and compared at phase comparator. The phase com-parator output signal is fed into a low-pass filter (Q302, Q303and Q304) before being applied to the VCO as a frequencycontrol voltage. This low-pass filter’s power is supplied bythe DC/DC converter (IC251 and Q251). The DC signal is ap-plied to the CV of the VCO and locked to keep the VCO fre-quency constant.PLL data is output from DT (pin 112), PCK (pin 82) and PLE(pin 81) of the microprocessor (IC404). The data are input tothe PLL IC when the channel is changed or when transmis-sion is changed to reception and vice versa. A PLL lock con-dition is always monitored by the pin 80 (UL) of the micropro-cessor. When the PLL is unlocked, the UL goes low.5. Control CircuitThe block diagram of the control circuit is shown in Fig-ure 5.The CPU (IC404) is a 16-bit microcomputer that contains a256k-byte Mask ROM and a 20k-byte RAM. This CPU is con-nected with an external 512k-byte Flash ROM (IC405) andoperates in memory expansion mode.The Firmware Program is stored in the Flash ROM and theuser data and adjustment data are stored in the EEPROM(IC401). The CPU and Flash ROM are connected with an 8 bitbus and the EEPROM and RTC IC : IC402 (TK-7180H only) areconnected with a I2C bus (*1). The RTC IC (TK-7180H only)has a clock function and is controlled by the CPU (IC404).Serial communication with a PC is performed through twopaths: through the 232C Level converter IC (IC416) andthrough the Display Unit Panel CPU (IC902). The 8 bit ShiftRegister (IC403) is used as an 8-port Extended Output Port.IC410 is an 8 bit-8ch D/A converter. The channels are set asfollows:Ch1 : Modulation balanceCh2 : Deviation FactorCh3 : Max Power LevelCh4 : Reception tuning circuitCh5 : Deviation FactorCh6 : Speaker volumeCh7 : VCXO control voltageCh8 : DEO output level*1: I2C bus is a registered trademark of PHILIPS of the Neth-erlands.LPFBPFBUFFVCOPLLCPU20155Doublerx2CVQ313BUFFQ311TCXOX301SWD316SW D315TodriveAMPQ301To mixer8FCBALIC408MBT/RT/R(TX : Low)IC301ULIC404DT,PCK,PLEQ302~Q304CIRCUIT DESCRIPTIONFig. 4 PLL block diagramIC405Flash ROMIC4038bit ShiftregisterIC410D/AconverterIC416232CLevelconverterIC902CPU(TK-7180H only)IC903 (TK-7180H)IC902 (TK-7182H)LCDdriverIC401EEPROMIC402RTC IC(TK-7180H only)Display unitIC415AQUA-LIC413MultiplexerSignal blockIC301PLL ICRF blockMaskROMIC404CPUFig. 5 Control circuit block diagram