Kenwood TK-860G Service Manual
Also see for TK-860G series: Instruction manualInstruction manualService manual supplementService manualService manual
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28TK-860G/862G EncodeThe QT and DQT signals are output from TO of the CPU(IC502) and summed with the external pin DI line by thesumming amplifier (IC2) and the resulting signal goes to theD/A converter (IC6) of the TX-RX unit. The DTMF and 2-TONE signals are output from DTMF of the CPU and goes tothe audio processor (IC508). The signal is summed with aMIC signal by the audio processor (IC508), and the resultingsignal passes through an analog switch (IC509) and goes tothe TX-RX unit (MO).The D/A converter (IC6) adjusts the MO level and the bal-ance between the MO and TO levels. Part of a TO signal issummed with MO and the resulting signal goes to the MDpin of the VCO. This signal is applied to a varicap diode inthe VCO for direct FM modulation. D/A ConverterThe D/A converter (IC6) is used to adjust TONE and MOmodulation, AF volume, TV voltage, FC reference voltage,and PC POWER CONTROL voltage level.Adjustment values are sent from the CPU as serial data.The D/A converter has a resolution of 256 and the followingrelationship is valid:D/A output = (Vin – VDAref) / 256 x n + VDArefVin: Analog inputVDAref: D/A reference voltagen: Serial data value from the microprocessor (CPU)Power Supply CircuitWhen the POWER switch on the control unit is pressed,the PSW signal goes low. This signal is inverted by Q26 andsent to a flip-flop IC (IC14). This IC outputs a control signalwhen the PSW goes low. When the power turns on, pin 1of IC14 outputs a low signal and Q20 turns on. The base ofQ19 goes high, Q19 turns on, SB SW (Q23) turns on andpower (SB) is supplied to the set.This circuit has an overvoltage protection circuit. If a DCvoltage of 20 V or higher is applied to the power cable, D21turns on and a voltage is applied to the base of Q21. Thisvoltage turns Q21 on and turns Q19 and SBSW off. Decode• QT/DQT/DTMFThe signal (DEO) detected by the TX-RX unit passesthrough two low-pass filters of IC513, goes to TOI of theCPU (IC502) to decode QT, DQT. The DTMF signal is de-coded by a dedicated IC (IC511) and the resulting signal issent to the CPU (IC502) as serial data.• 2-toneThe detected signal passes through audio processor(IC508) RX OUT. Then it is filtered through IC504 2-stagelow-pass filtered to enter CPU (IC502) to decode 2-tone sig-nalling.CIRCUIT DESCRIPTIONFig. 14 EncodeFig. 15 DecodeX1VCXOIC6D/AA1VCOIC1SUMAMPIC509AnalogSWIC508AudioprocessorIC3PLLMBMDMOTOHTDIMICTX-RX UNITTODTMFIC502CPUIC502CPUIC513(2/2)LPFIC513(1/2)LPFTOIIC511DTMFDECO.IC508AudioprocessorSTDDEOIC514(2/2)LPFIC514(1/2)LPF2TN RXOUTQ23SWQ19SWQ20SWQ26INV.IC14F.F.Q21SWD21SWR135R134IGNSB +BPSWFig. 16 Power supply circuit |
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