Kenwood TM-D710A Service Manual

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Contents

TM-D710A/D710E53-5. TNC SectionThe reception data signal from the main unit is inputto the panel section through the PRI terminal (pin 8 of themodular jack of the panel section). This signal is the sameas the PR9 signal of the DATA terminal. So, the data signalenters the panel section through the same route for both1200bps and 9600bps.The reception data signal from the PRI terminal passesthe LPF (gain: 0, cutoff frequency: 4.8kHz) of IC22, adjuststhe output with the electric volume (IC20) and the datasignal enters the operational amplifier (IC10). The outputadjustment value of the electric volume is fixed. The datasignal of 1200bps and 9600bps is divided with the op-amp (IC10). Each data signal passes the buffer amp and isconverted to a logic signal by the comparator (IC17).The logic signal converted with the comparator entersto the TNC ASIC (IC12). The signal is demodulated with theTNC ASIC and is then processed with the TNC MPU (IC11).For packet mode, signals processed with the TNC MPUenter to the panel MPU. The digital signals are not changedin the panel MPU. The level of the signal is changed withthe RS-232C driver IC (IC7) and the signals are then outputfrom the COM terminal (J2).In APRS mode, the signal entering the panel MPU isprocessed and the status is displayed on the LCD.The TNC section uses the same 3-chip TNC as theTM-D700. The flash-type TNC MPU is used and thefirmware can be rewritten. The MPU clock operates atdouble frequency. TNC ASIC is an existing product. So, thefrequency of the clock signal is divided by half with the flip-fl op (IC16).T h e S - R A M ( I C 1 3 ) h a s a c a p a c i t y o f 4 M b i t s i norder to operate smoothly in the KISS mode of packetcommunication.CIRCUIT DESCRIPTION3-2. Key, Encoder, Volume Input CircuitThe panel section key corresponds to the panelMPU port, one-to-one. The POWER key is pulled up andconnected to the interrupt port of the panel MPU.Other keys are also pulled up outside because the panelMPU is an 8 bit data bus mode. The scanning process readsout the status of the keys. So, if a key is in the ”L” level, noother keys are accepted.The encoder is connected to the panel MPU and the portis pulled up.The volume (VOL/SQL) divides the 5V voltage, readswith the A/D port of the panel MPU and transfers the datato the main unit section MPU (IC918).3-3. Display CircuitThe LCD is a COF (Chip On Flexible printed circuitboard) type with the driver IC mounted on the FPC andcontrolled by the 8 bit data bus mode. The voltage ”V3”is approximately 12V for the LCD, but due to the voltagebooster function of this driver IC, it can operate with a singlepower of 5V.The contrast can change this ”V3” voltage by 16 steps,using the internal memory of the driver IC.3-4. Brightness CircuitThe illumination color can be set to either amber orgreen.The PWM signal output from the panel MPU passesthrough the LPF, is converted into DC voltage, and controlsthe current that flows to the LED with the transistor. Theduty of the PWM changes the LED brightness to one ofeight levels or OFF.AMBERGREENCurrentcontrolIC1PanelMPUQ5Q4SWLPFPWM 10VCurrentcontrolQ7Q6SWLPFPWM 10VFig. 2 Brightness circuit