Icom ic-f3062t Service Manual

Also see for IC-F3061S: Adjustment Servise manual Instruction manual Service manual Instruction manual

Contents

Icom ic-f3062t Service Manual Manual pdf 10 page image

Poweramp.ALCamp.Driveamp.+–HV“ISENS”• APC CIRCUITto the anntena“T2”“TMUT”from TX/RX switch(MAIN UNIT; D14, D15)T5VQ604, Q605Q602Pre-driveamp.Q603IC601Q601to the receive circuitsLPF LPFANTSWCurrentdetectorD604Power detecterD605Q606The output AF signals are then passed through the Digital/Analog switch (IC14, pins 12, 14) and applied to the AF mixer(IC9, pin 6) where the MIC signals and Tone signals are mixedwith (while CTCSS/DTCS are in use) via the PM/FM switch(IC13, pins 12, 14).The CTCSS and DTCS signals are generated by the CPU(IC18) and output from pins 89−91. The output signals arepassed through the 3 registers (R263–R265) to change its waveform. The wave form changed CTCSS/DTCS signals are passedthrough the LPF (IC17, pins 1, 3) and the D/A converter (IC4,pins 21, 22) for level adjustment. The level adjusted CTCSS/DTCS signals are then applied to the AF mixer (IC9, pin 6).2/5 tone and DTMF signals are generated by the CPU (IC18)and output from pin 43. The output signals are passed throughtwo LPF's (IC17, pins 8, 10 and pins 5, 7), then applied to the AFmixer (IC9, pin 6).The mixed AF signals are output from pin 7 of the AF mixer(IC9) and passed through the D/A converter (IC4, pins 3, 4)for level adjustment (=deviation adjustment), then applied tothe modulation circuit (D9) as the modulation signals. Themodulation signals are also applied to the reference frequencyoscillator (X1) via D/A converter (IC4, pins 11, 12) and AFamplifi er (IC21, pins 1, 4).5-2-2 MODULATION CIRCUIT (MAIN UNIT)The modulation signals from the microphone amplifier circuitsare applied to the D9, and modulate the VCO oscillatingsignal by changing the reactance of D9. The modulated VCOoutput signal is buffer-amplified by Q4 and Q6, then applied totransmit amplifiers as a transmit signal via the TX/RX switch(D14 is ON, D15 is OFF).5-2-3 TRANSMIT AMPLIFIERS (RF UNIT)The transmit signal from the TX/RX switch (MAIN UNIT; D14is ON, D15 is OFF) is amplified to the transmit output level bypre-driver (Q603), driver (Q602) and power (Q601) amplifi ers.The power-amplified transmit signal is passed through thetwo LPF’s (L607, L608, C620, C622−C624, C664 and L606,C615−617) to filter off the harmonic components in thetransmit signal. The filtered transmit signal is passed throughthe antenna switching circuit (D601 and D603 are ON), thenapplied to the antenna connector (CHASSIS; J1) via anotherLPF (L601−L603, C601, C602, C604−C606, C608, C609, C663).5-2-4 APC CIRCUIT (RF UNIT)The APC (Automatic Power Control) circuit stabilizes transmitoutput power to prevent the transition of the transmit outputpower level which is caused by load mismatching or heateffect, etc. The APC circuit also selects transmit output powerfrom high, middle and low power.A portion of the transmit signal is detected by the transmit powerdetector (D604, D605) to produce a DC voltage corresponding tothe transmit output power level. The detected voltage is appliedto the APC amplifier (IC601, pin 3). The transmit power settingvoltage “T2” from the D/A converter (MAIN UNIT; IC20, pin 2) isapplied to another input terminal (pin 1) as the reference voltage.The APC amplifier compares the detected voltage and referencevoltage, and the difference of the voltage is output from pin 4.The output voltage controls the bias of the drive (Q602) andpower (Q601) amplifiers to reduce/increase the gain of theseamplifiers for stable transmit output power.The change of transmit output power is carried out by thechange of reference voltage "T2," and the transmit powermuting is carried out by the TX mute switch (Q606), using the“TMUT” signal from the CPU (IC18, pin 13).5-2-4 OVER CURRENT DETECTION CIRCUIT (RF UNIT)The driving current of the drive (Q602) and power (Q601)amplifiers is detected at the current detector (Q604, Q605)by detecting the difference of voltage between both terminalsof R623. The detected voltage "ISENS" is applied to the CPU(IC18, pin 47).In case of the over current, the CPU outputs "TMUT" signalfrom pin 13 to TX mute switch (Q606) to stop the transmittingfor protection of transmit amplifi ers (Q601, Q602).5-3 PLL CIRCUITS5-3-1 VCO (Voltage Controlled Oscillator) CIRCUITS(MAIN UNIT)A VCO is a oscillator which its oscillating frequency iscontrolled by adding voltage (lock voltage).This transceiver has 3 VCO’s; RX VCO1 (Q1, D1−D4), RXVCO2 (Q2, D5−D8) and TX VCO (Q3, D10−D12). The RXVCO1 oscillates the 1st LO signals for 155 MHz and higher,and the RX VCO2 oscillates the 1st LO signals for 155 MHzand lower frequencies. And the TX VCO oscillates the transmitoutput signal.• RX VCO1 and RX VCO2The RX VCO1/RX VCO2 (Q1, D1−D4/Q2, D5−D8) oscillatesthe 1st LO signals. The output signals are amplified by thebuffer amplifi ers (Q4, Q6), and applied to the 1st mixer (Q37)via TX/RX switch (D14 is OFF, D15 is ON) and LPF (L38,L39, C161−C164, C383, C384), to be mixed with the receivedsignals to produce the 46.35 MHz 1st IF signal.• TX VCOThe TX VCO (Q3, D10−D12) oscillates the transmit signal.The output signal is applied to the transmit amplifiers via thebuffer amplifiers (Q4, Q6) and TX/RX switch (D14 is ON, D15is OFF).5 - 3