Kenwood NXR-710 Service Manual

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

NXR-710164-6. Power supply voltage monitoring circuitThe X53-449 circuit consists of IC307, IC308, D303 andQ301.IC308 is a voltage detect IC and is used to generate the“/RST” signal for the MCU (IC20).This “/RST” signal is connected to the hardware resetpin of MCU (IC20).IC307 is a voltage detect IC and is used to generate the“/BINT” signal for the MCU (IC20).This “/BINT” signal is connected to the hardware inter-rupt pin of MCU (IC20). The software of the MCU (IC20)runs to the sleep-mode to use the “/BINT” signal.D303 and Q301 are used to generate the “OVRB” signalfor the MCU (IC20). The software of the MCU (IC20) runs tothe sleep-mode to use the “OVRB” signal.SWSWCN301DC-DCIC301RESETIC308AVRIC302AVRIC30360DC33MAVRIC30516MAVRIC30415M/BINTIC307/BINT/OVRBQ301ORQ401/OVRBAVRIC30633A50M/RSTQ303 33BUQ402AMP_BAMP_SWBSBFig. 15 Power supply circuit4-7. 18.432MHz clock circuitThe 18.432MHz clock is provided to the MCU (IC20),DSP(IC6), and DAC (IC14) of the Squelch circuit.4-8. Audio circuit■ Audio amplifier circuitThe audio amplifier circuit is located in the control sec-tion of the Control unit (X53-449). The 4W output audiopower is available from the pin 15 TEST/SPKR connector“SPO”, “SPG” on the rear panel to the external speaker inthe case of a power supply voltage of 13.6V and a 4Ω load.■ Microphone circuitThe signal from the microphone is passed through theAGC circuit located in the Display unit (X54-358 A/2) so thatit may not saturate. This circuit consists of IC501, D501,D502 Q501, and Q502. The AGC controls the amplifier gainsusing the detected audio signal depending on the positiveand negative peaks of the signal amplitude. The audio sig-nal goes to the control section of the Control unit (X53-449)from the Display unit (X54-358 A/2).■ Modulation circuit (Analog/Digital signal processing)In the case of the Analog Signal Processing mode, thetransmitting audio signal is amplified by IC405 (C/4), input tothe MICADCO terminal of the MCU (IC20), and audio pro-cessed by DSP (IC6). The processed audio signal from theMODDAC terminal of IC20 is passed through an anti-aliasingfilter at IC404 (A/2), and is then amplified to a sufficient levelby IC404 (B/2), and amplified by the summing (TD) amplifier.The Digital Signal Processing mode is the same as the Ana-log Signal Processing mode.4-9. Other circuit■ Real-time clockThe clock function is based on a real-time clock IC (IC17).When the power supply is off, it is backed up by an internalsecondary lithium battery.CIRCUIT DESCRIPTION