Kenwood TK-8302 Service Manual

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Contents

TK-8302/8302H135-1. Memory CircuitThe transceiver has a 256k-bit EEPROM (IC703). The EE-PROM contains adjustment data. The MCU (IC702) controlsthe EEPROM through three serial data lines.EEPCKIC702MCUIC703EEPROMEEPDIEEPWPFig. 11 Memory circuit5-2. Display CircuitThe MCU (IC702) controls the 7-segment LED Displayand LEDs.When power is on, the MCU will use the MBL line tocontrol the key backlight LEDs.When the transceiver is busy, the GLED line goes high,Q1 turns on and the green LED (D23) lights after Q7 turnson. In transmit mode, the RLED line goes high, Q2and Q8turn on and the red LED (D23) lights.BLED will be set high when the function select (FPU set-ting) is on, Q6 turns on and the blue LED (D22) lights.The dimmer function is controlled by the switch (Q5).The LED driver (IC1) controls the functions of the 7-segmentLED through the LEDI, LECE, LECL, LELH lines from theMCU.Q3SWQ4SWQ5SWD1~D5Key backlightDisplay7-segmentIC702MCUIC1LEDdriverLEDILEDMLECELECLLELHMBLQ1SWQ7SWD23GLEDQ2SWQ8SWRLEDQ6SWD22BLEDFig. 12 Display circuit5-3. Key Matrix CircuitThe TK-8302 front panel has function keys. Each of themis connected to a cross point of a matrix of the KMI1 toKMO3 ports of the MCU. The KMO1 to KMO3 ports are al-ways high, while the KMI1 to KMI3 ports are always low.The MCU monitors the status of the KMI1 to KMO3ports. If the state of one of the ports changes, the MCU as-sumes that the key at the matrix point corresponding to thatport has been pressed.IC702MCUKMO1KMO2KMO3KMI3KMI2KMI1BCH UPVOL DNArVOL UPSCCH DNFig. 13 Key matrix circuit6. Signaling Circuit6-1. Encode■ Low-speed data (QT, DQT)Low -speed data is output from pin 1 (LSDO) of the MCU(IC702). The signal passes through a low-pass CR filter. Thesignal is mixed with the audio signal and goes to the VCOand TCXO (X1) modulation input after signal processing inthe baseband IC (IC701).■ High-speed data (2-tone)High-speed data (HSD) is output from pin 2 (HSDO) ofthe MCU.The signal passes through a low-pass CR filter. TX devia-tion making an adjustment by MCU is applied to the base-band IC (IC701). The signal is mixed with the audio signaland goes to the VCO and TCXO.The RX tone is audio output of the baseband IC (IC701)at the same time to audio power amplifier and then to thespeaker.X1TCXOVCOIC701Baseband ICDTMF/MSKIC1PLLTCXOMODVCOMODQT/DQTLSDO2-TONEHSDOIC702MCUFig. 14 Encode■ MSK / DTMFMSK and DTMF signal is self generated by the basebandIC (IC701).The TX deviation adjustment is done by the output gainof the baseband IC (IC701), and is routed to the VCO. Whenencoding MSK/DTMF, the microphone-input signal is muted.6-2. Decode■ Low-speed data (QT, DQT)The demodulated signal from the FM IC (IC500) will inputto the baseband IC (IC701) to remove frequencies of 300Hzor more.The signal is input to pin 88 (LSDI) of the MCU. TheMCU digitizes this signal, performs processing such as DCrestoration, and decodes the signal.CIRCUIT DESCRIPTION