Kenwood TK-7302 Service Manual

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TK-7302/7302( V ) /7302H/7302H ( V )14■ High-speed data (2-tone)The demodulated signal from the FM IC (IC500) is am-plified by the baseband IC and passes through a high-passfilter to remove frequencies of 3kHz or more. The MCU digi-tizes this signal and decodes the signal after receiving thesignal at pin 87 (HSDI).■ MSK/ DTMFThe demodulated signal from the FM IC (IC500) willinput to the baseband IC(IC701), then the baseband IC willdecode and send the decoded information to the MCU bythe data line.The MCU then processes the decoded information.IC701Baseband ICDTMF/MSKdecode IC702MCUQT/DQTLSDIDTMF/MSKdecode dataREPLAY data2-TONEHSDOIC500FM ICFig. 15 Decode7. Power Supply CircuitWhen the power switch on the display unit is pressed,the power port on the display unit which is connected toport 17 (POWER), goes low, then port 52 (SBC) goes high,Q719 turns on, SB switch (Q720) turns on and power (SB) issupplied to the transceiver.When the DC power is supplied to the transceiver, thevoltage regulator IC (IC707, IC706) and supply into the MCUVDD and reset the voltage detect IC (IC709). IC709 willgenerate signal (RESET) into the reset terminal on the MCU(IC702) to carry out a power on reset. Also, MCU (IC702) ischecking on port 91 (BATT). If DC power is less than about8.5V, the transceiver is unable to power on.When the DC power voltage deceases from normal volt-age, the INT voltage detector IC (IC708) will set to high onMCU port 18 (INT). If B line becomes less than about 8.5V,MCU will send the backup data to EEPROM (IC703) and gointo STOP mode.This circuit has an overvoltage protection circuit. If a DCvoltage of 16V or higher is applied to the base of Q710, thisvoltage turns Q710 on and sets port 18 (INT) to low. As a re-sult port 78 (SBC) is low, and turns Q719 and Q720 (SB) off.Fig. 16 Power supply circuitQ707SWQ720SWQ719SWIC707AVRD715BIC709AVRIC706AVRSBCIGNR792R793R851R852INT5M3.3MBATTIC702MCUPOWERSWPOWERRESETIC708AVRQ710SWSBIGNCIRCUIT DESCRIPTION