Kenwood TK-860G Service Manual

Also see for TK-860G series: Instruction manual Instruction manual Service manual supplement Service manual Service manual

28TK-860G/(N)/862G/(N) 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-tone, 5-toneThe detected signal passes through audio processor(IC508) RX OUT. Then it is filtered through IC514 2-stagelow-pass filtered to enter CPU (IC502) to decode 2-tone and5-tone signalling. PA SwitchIf the optional KAP-1 is used (see the separate section fordetails), the PA (Public Address) function becomes avail-able. In this case, the signal flow changes as follows;• PA offFor TX, the switch which is between pins 10 and 11 ofIC509 closes. The audio signal from the microphone passesthrough IC509 and IC6 and modulates the VCO.For RX, the switch which is between pins 3 and 4 ofIC509 closes. The detected signal passes through IC509,IC508, IC507, IC6 and IC13 and is then output to thespeaker.• PA onSince the switch which is between pins 10 and 11 ofIC509 is open, the switch which is between pins 3 and 4 ofIC509 is open, and the switch which is between pins 1 and 2of IC509 is closed, the audio signal from the microphonepasses through IC508, IC507 and IC6, and then goes toIC13. The signal is output to the external PA systemthrough the PA relay in KAP-1. 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) Horn ControlThe horn switch, consisting of Q1, Q5, and Q6, controlsthe horn relay. It is supplied by the dealer to provide theexternal horn alert function.Q6 disables horn alert, turning on when its base is high,to inhibit the function. Normally, the output from IC9 is low,and Q5 is off; the base of Q1 is about 0V and Q1 is off.When horn alert is enabled, the output from IC9 goes highand Q5 turns on. The base current flows through R21 to Q1to turn Q1 on. Q1 can sink a maximum of 100mA. If theoptional KAP-1 is used, it can drive up to 2A.CIRCUIT DESCRIPTIONFig. 14 DecodeIC502CPUIC513(2/2)LPFIC513(1/2)LPFTOIIC511DTMFDECO.IC508AudioprocessorSTDDEOIC514(2/2)LPFIC514(1/2)LPF2TN RXOUTQ23SWQ19SWQ20SWQ26INV.IC14F.F.Q21SWD21SWR135R134IGNSB +BPSWFig. 17 Power supply circuit8C HORD2Q1Q5R21Q6R3R135+BIC9 HNCIGNPower 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.10241113DEOMBVCOMIC IC507 IC508 IC509IC6OP AMP Audioprocessor Analog SWD/Aconverter IC13Power AMPSP(INT/EXT)PAKAP-1(Option)Fig. 15 Horn control circuitFig. 16 PA switch