Kenwood TK-7180 Service Manual

Also see for TK-7180: Modification Information Function reference Brochure & specs Specification Instruction manual

TK-7180161. OutlineThe TK-7180 is a VHF/FM transceiver designed to operatein the frequency range of 136 to 174MHz. Transmission out-put power is 30 watts. The maximum channel capacity is512.The unit consists of receiver, transmitter, phase-lockedloop (PLL) frequency synthesizer, and control circuits.2. Receiver CircuitThe receiver is double conversion superheterodyne, de-signed to operate in the frequency range of 136MHz to174MHz.The receiver circuit consists of the following : 2-1 front-end circuit, 2-2 first mixer, 2-3 IF amplifier circuit, 2-4 audioamplifier circuit, and 2-5 squelch circuit.2-1. Front-end CircuitThe front-end circuit consists of former BPF (D11), RF am-plifier Q103, and latter BPF (D103, D104, D105 and D106).The BPF covers frequency ranges 136 to 174MHz.The latter BPF (D103, D104, D105 and D106) attenuatesthe unwanted signals, and sends only the necessary signal tothe first mixer.2-2. First MixerThe signal from the BPF is heterodyned with the first localoscillator signal from the PLL frequency synthesizer circuit atthe first mixer DBM (IC171) to become a 44.85MHz first in-termediate frequency (IF) signal. The first IF signal is fedthrough a monolithic crystal filter (XF171) to further removespurious signals.2-3. IF AmplifierThe first IF signal is amplified by Q171 and Q172, and thenenters IC172 (FM system IC). The signal is heterodynedagain with a second local oscillator signal (44.395MHz) within IC172 to become a 455kHz second IF signal. The secondIF signal is fed through a 455kHz ceramic filters (CF172;Wide, CF171; Narrow) to further eliminate unwanted signal,and the quadrature detection circuit FM-detects the signal toproduce a base-band signal and output it from pin 9.2-4. Audio AmplifierThe demodulated audio signal from IC172 goes to IC415through the AF amplifier (IC412) and IC413. The audio signalgoes to an electronic volume (IC410) and is amplified to drivea loudspeaker by an audio power amplifier (IC417). The audiooutput can be provided to external 4Ω speaker through thespeaker jack output (J401) on the rear panel. Q419 is a muteswitch.IF AMPQ172IF AMPQ171SWCFSWCF171(Narrow)CF172(Wide)D171D172455kHzDETNOISE DETD173SWW/NQ178SWCFSW44.85MHz1st MIX DBMIC171BPFD103~D106RF AMPQ103 BPFD11NOISEAMPQ175QUDFM SYSTEM IC : IC172RSSIDETSQLX17144.395MHzQ306Buff AMPQ311Buff AMPQ313LPFfRX+44.85MHzRX VCOAMPIC412 (B/2)AQUA-LIC415CPUIC404IC407DEOMUTEQ419AFAMPIC417AFODACIC410SWIC413DACIC410ASQRSSIINT. SP136~174MHzRX ANTTX-RX UNIT (X57-698)MCF MCFXF171(2/2)XF171(1/2)180.85~218.85MHzCIRCUIT DESCRIPTIONFig. 1 Receiver circuit