Kenwood NXR-710 Service Manual

Also see for NEXEDGE NXR-710: Instruction manual Instruction manual Instruction manual Instruction manual Instruction manual

NXR-710143-2. CM coupler circuitThe CM coupler circuit is a line for detecting forwardwave and reflected wave. Forward wave is detected by D3,and is converted into DC voltage. If an abnormal antennaload is connected, reflected wave is detected by D4 andconverted into DC voltage.3-3. Filter circuitThis circuit removes harmonics from the transmitter out-put and sends filtered signals to the antenna.3-4. APC circuitThe automatic transmission power control (APC) circuitstabilizers the transmitter output power at a pre-determinedlevel. DC voltage from the CM coupler circuit is amplified bythe DC amplifier IC202 (1/2). IC202 (2/2) compares the APCcontrol voltage (RAMP) generated by the MCU (X53-449)and the DC amplifier IC201 (1/2, 2/2) with the output voltagefrom IC202 (1/2) to control the gate voltage for amplifier Q3and fi nal amplifier Q4.3-5. High temperature detector circuitTo prevent thermal destruction of amplifier Q3 and finalamplifier Q4, this circuit reduces the APC control voltage(RAMP) when the temperature of amplifier Q3 and fi nal am-plifier Q4 rises. The MCU detects the temperature with thethermistor (TH201) and controls the APC voltage (RAMP).3-6. FAN action control circuitThe FAN action control circuit consists of the FAN andswitching transistor Q207. It is controlled by the MCU (X53-449). If the FAN action is set to “Temperature”, the coolingfan is turned ON or OFF according to temperature. If theFAN action is set to “Continuous”, the cooling fan operatescontinuously, but Q207 stays ON.3-7. AVR circuitThe 13.6V power source (+B) is provided through con-nector CN201 to the Final unit (X45-392 A/3). +B is con-nected to CN203 to supply the 13.6V power source for theTX-RX unit (X57-794). +B is a power source for the “finalamplifier”, “drive amplifier” and fan. IC203 regulates the +Bvoltage to 8V. This 8V power source is connected to the FETswitches Q203, Q204, Q205, and Q206. Q204 and Q206are controlled by the “8TC” signal from the I/O expander ICwhich is in the TX-RX unit (X57-794). If “8TC” logic is high,Q204 and Q206 turn on and supply the 8V power sourceto the APC circuit and pre drive amplifiers. Q203 and Q205are controlled by the “ASWC” signal from the I/O expanderIC which is in the TX-RX unit (X57-794). If “ASWC” logicis high, Q203 and Q205 turn on and supply the 8V powersource to the antenna switch circuit.Drive AMPSW8TCQ204,Q206SWASWCQ203,Q205CN201+Bfrom Final unit(X45-392 B/3)+Bto TX-RX unit(X57-794)Final AMPFAB8V AVRIC20380T80SWCN203Fig. 13 AVR circuit4. Control unitThe Control unit (X53-4490-10) consists of the followingcircuits:(1) MCU circuit(2) Memory circuit(3) DSP circuit(4) Squelch circuit(5) Power supply circuit(6) Power Supply Voltage Monitoring Circuit(7) 18.432MHz clock circuit(8) Audio circuit(9) Other circuit4-1. MCU circuitThe MCU (IC20) is a 32bit RISC processor, equipped witha peripheral function and ADC/DAC.This MCU operates at a 18.432MHz clock and 3.3V/1.5VDC.It controls the flash memory, SRAM, DSP, receive circuit,transmitter circuit, and control circuit.CIRCUIT DESCRIPTION