Kenwood TK-2317 Service Manual

Also see for TK-2317: Service manual Specification Instruction manual Instruction manual

Contents

TK-2317232-5. Audio Amplifier CircuitThe demodulated signal from IC401 is sent to an audiopower amplifier (IC815) through baseband IC (IC812), whereit is amplifi ed and output to the speaker.2-6. Squelch CircuitPart of the AF signal from the IC401 enters the FM sys-tem IC (IC401) again, and the noise component is amplifiedand rectified by a filter and an amplifier to produce a DCvoltage corresponding to the noise level.The DC signal from the FM IC goes to the analog port ofthe MCU (IC820). IC820 determines whether or not to outputsounds from the speaker by checking if the input voltage ishigher or lower than the preset value.To output sounds from the speaker, IC820 sends a highsignal to the AF_CONT line and turns IC815 on throughQ813, Q814, Q818 and Q819.3. Transmitter System3-1. Microphone Amplifier CircuitThe signal from the microphone is limited by the AGCcircuit, which is composed of D807, D808, Q810, Q811 andthe mute switch (Q809). IC812 is composed of a high-passfi lter, low-pass fi lter and pre-emphasis/IDC circuit.The signal from the microphone and the low speed datafrom the MCU (IC820) enter the baseband IC (IC812) andpass through each path and are mixed inside the IC.The output signal from the baseband IC goes to the VCOmodulation input. The other output signal passes through theamplifi er (IC3) and goes to the TCXO modulation input.CIRCUIT DESCRIPTION / 电路说明3-2. Driver and Final Amplifier CircuitThe signal from the T/R switch (D18 is on) is amplified bythe RF AMP (Q201) and pre-drive amplifier (Q203) to 50mW.The output of the pre-drive amplifier is amplified by thedrive amplifier (Q204) and the RF final amplifier (Q205) to5.0W (1W when the power is low).The drive amplifier and the RF final amplifier consist oftwo MOS FET stages.The output of the RF final amplifier is then passedthrough the antenna switch (D201 and D202) and the har-monic fi lter (LPF), and is applied to the antenna terminal.AMPIC3AGCSWD807,808Q810,811MIC_MTX1TCXOVCOLSDOUTIC812Q809MICBasebandICFig. 4 Microphone amplifier circuit / 图 4 麦克风放大器电路2-5. 音频放大器电路来自于 IC401 的解调信号，并通过 IC815 送到 AF 放大器，在音频功率放大器 (IC815) 进行放大后输出到扬声器。2-6. 静噪电路FM IC(IC401) 输出的 AF 信号的一部分再进入 IC，噪声成份通过滤波器和放大器进行放大和修正，生成与噪声电平相应的 DC 电压。DC 信号通过 FM IC 被送到微处理器的模拟端口微处理器(IC820)。IC820 通过检测输入的电压是高于还是低于预设值来决定是否从扬声器输出声音。由扬声器输出声音时，IC820 发送高电平信号给 AF_CONT，通过 Q813、Q814、Q818 和 Q819 打开 IC815。3. 发射机系统3-1. 麦克风放大器电路麦克风的信号被并受由 D807,D808,Q810 和 Q811 组成的AGC 电路的限幅，然后通过静音开关 (Q809)。IC812 由高通滤波器、低通滤波器和预加重 /IDC 电路组成。麦克风的信号和从微处理器来的低速数据进入基带 IC 后这些信号在 IC 内部被混合。基带 IC 的输出信号送入 VCO 调制输入。基带 IC 的其他输出信号送入 TCXO 调制输入。3-2. 驱动器和终端放大器电路来自于 T/R 开关 (D18 ON) 的信号被预驱动放大器 (Q203)和驱动放大器 (Q204) 放大到 50mW。驱动放大器的输出被 RF 功率放大器 (Q205) 放大到 5.0W( 当低功率时为 1W)。RF 功率放大器由 2 个 MOS FET 构成。RF 功率放大器的输出通过谐波滤波器 (LPF) 和天线开关(D201 和 D202) 并且送到天线终端。