Kenwood TK-7160 Service Manual

Also see for TK-7160: Instruction manual Service manual Specifications Brochure & specs Instruction manual

TK-716014■ Unlock CircuitDuring reception, the 8RC signal goes high, the 8TC signalgoes low, and Q44 turns on. Q43 turns on and a voltage isapplied to the collector (8R). During transmission, the 8RCsignal goes low, the 8TC signal goes high and Q46 turns on.Q45 turns on and a voltage is applied to 8T.The CPU in the control unit monitors the PLL (IC401) LDsignal directly. When the PLL is unlocked during transmis-sion, the PLL LD signal goes low. The CPU detects this sig-nal and makes the 8TC signal low. When the 8TC signal goeslow, no voltage is applied to 8T, and no signal is transmitted.Transmitter System■ OutlineThe transmitter circuit produces and amplifies the desiredfrequency directly. It FM-modulates the carrier signal bymeans of a varicap diode.■ Power Amplifier CircuitThe transmit output signal from the VCO passes throughthe transmission/reception selection diode (D448) and ampli-fied by Q501, Q502 and Q503. The amplified signal goes tothe final amplifier (Q504) through a low-pass filter. The low-pass filter removes unwanted high-frequency harmonic com-ponents, and the resulting signal is goes the antenna termi-nal.■ APC CircuitThe automatic transmission power control (APC) circuitdetects part of a final amplifier output with a diode (D606,D607 and D608) and applies a voltage to IC651. IC651 com-pares the APC control voltage (PC) generated by the D/A con-verter (IC201) and DC amplifier (IC214) with the detectionoutput voltage. IC651 generates the voltage to control Q502,Q503 and Q504 and stabilizes transmission output.The APC circuit is configured to protect over current ofQ502, Q503 and Q504 due to fluctuations of the load at theantenna end and to stabilize transmission output at voltageand temperature variations.Fig. 7 Unlock circuitIC101CPUQ44SWQ43SWIC401PLLQ46SWQ45SWLD8RC8C8R 8T8TCPLL lock: LD “H”Fig. 8 Transmitter systemFig. 9 APC circuitRFAMPQ501DRIVEAMPQ503FINALAMPQ504PREDRIVEAMPQ502DCAMPIC214ANTSWD602D603,D605LPFANTPOWERDETD606D607D608IC651 VR1APCCONTROLD448PCIC2013pinANTIC211MICMIC/IDCIC213SWIC101CPUQ444TXVCOQ446BUFFQ447RFAMPQ501RFAMPQ502PREDRIVEAMPQ503DRIVEAMPQ504FINALAMPIC4021/2DIVIDERPLLTCXO16.8MHzMIC KEYINPUTIC241AQUQICIC201IC201D/ACONV.D/ACONV.X401 IC401RFAMPQ431CIRCUIT DESCRIPTION