Kenwood TK-5210 Service Manual

Also see for TK-5210: Specifications Instruction manual Specifications Instruction manual Instruction manual

Contents

TK-521014CIRCUIT DESCRIPTION3-5. Audio Amplifier Circuit• AF signalThe AF signal from CODEC (IC406) is amplified by IC407and goes through IC408.The AF signal goes through a DAC (IC411), an AF amplifier(IC603), and an AF switch (IC604), and is routed to audiopower amplifier (IC601), where the signal is amplified andoutput to the internal speaker.• Audio circuitCODEC (IC406) extracts the audio signal from the receivesignal in the detection circuit in FM mode. The signal is thendeemphasized and output as a decoded audio signal in APCOmode.LPF (IC407) removes quantization noise from the audiosignal output of the CODEC.The switch (IC408) stops the audio signal of the CODEC toprevent the mixing of BEEP, voice announcement and audiosignal when the BEEP or voice announcement is output fromthe CPU. If an optional scrambler board is installed, the audiopath is adjusted so that the audio signal goes through thescrambler board.DAC (IC411) controls the voltage amplitude level of theaudio signal according to the volume position of thetransceiver. This determines the volume level output fromthe speaker.The amplifier (IC603) amplifies the audio signal so that theaudio signal level at the final stage amplifier is appropriate.The volume levels of the 8Ω internal speaker and 16Ωexternal speaker are matched using the EXT AFC.The switch (IC604) adjusts the signal path so that theaudio signal is output to the audio amplifier (IC602) forexternal speakers when optional external speakers areconnected. If no external speakers are connected, the audiosignal is output to the audio amplifier (IC601) for the internalspeaker.IC601 and IC602 output is BTL (Bridge Tied Load).• AF controlSpeaker switching is performed by the CPU (IC5) usingINT AFC or EXT AFC. First, the logic level at the speakersswitching terminal (SSW) on the universal connector is fed tothe CPU. The CPU then outputs data based on this input.When there is no SP-MIC installed, this logic levelbecomes high. When the INT AFC is high, the EXT AFC goeslow, so the AF signal is only fed to the amplifier for theinternal speaker (INT SP) of IC601.However, when a SP-MIC has been connected, this logiclevel becomes low, so the INT AFC goes low and the EXTAFC goes high. In this case, the AF signal is fed only toamplifier for the external speaker (EXT SP) of IC602.3-6. Squelch CircuitIt amplifies the demodulated noise signal from FM IC(IC204) after filtering through BPF circuit. Then, the amplifiedsignal is converted to DC signal by the detection circuit. Theconverted signal is fed to the CPU (IC5).4. Transmitter System4-1. Audio Band CircuitThe audio band circuit of the transmitter system consistsof the following:• Microphone (Main)• Microphone (Sub)• N/C amplifier (Noise canceling mic amplifier) (IC603)• Switch (Int/ext) (Q410)• Switch (Mic mute) (Q406)• AGC (IC405, D402, D403)• Switch (Scrambler board) (Q407)This transceiver has two types of microphones: main andsub. The main microphone is located at the front of thecabinet and the sub microphone is located at the rear of thecabinet. The audio signal input from these microphones issynthesized by the N/C amplifier (IC603). The audio signalfrom the main microphone is synthesized in normal phaseand the audio signal from the sub microphone is synthesizedin opposite phase. So if the same audio signal is applied in thesame phase to the main and sub microphones, it is cancelledby the N/C amplifier. If audio signal is input to only the main orsub microphone, it is not cancelled, but output from the N/Camplifier.This prevents ambient noise from entering the audio bandcircuit at the next or subsequent stages.When an optional external speaker microphone isinstalled, the Int/ext switch (Q410) cuts off the audio signalfrom the main and sub microphones and sends only the audiosignal from the external microphone to the next stage.The microphone mute switch (Q406) cuts off audiosignals from the main, sub and external microphones.AGC (IC405, D402, D403) is an amplifier that reduces gainautomatically by greatly increasing the attenuation when theaudio signal of a certain level or higher is present. It controlsthe gain so that the audio signal input to the CODEC (IC406)is not clipped.If an optional scrambler board is installed, the switchFig. 4 Audio circuit diagramFig. 5 Squelch circuitIC403LPF AMPQ412Noise AMPD404DETIC5CPUBEEPS/SCSWTX-RX (X57-682 A/5) CONTROL (X57-682 B/5)BEEP/voice announce EXT AFC EXT AFCINT SPIC406CODECIC407LPFIC411DACIC603AMPIC604SWuniversal connectorEXT SPScrambler boardIC8DSPINT AFCIC601AMPIC602AMPIC408SW