Kenwood TK-280 Service Manual

Also see for TK-280: User manual Instruction manual Instruction manual Pricing and specification manual Service manual

Contents

TK-28025CIRCUIT DESCRIPTION8. Power Supply CircuitBattery +B is supplied via a 3A fuse from the battery terminalconnected to the TX-RX unit. After passing through the powerswitch, power supply (SB) is applied to the three AVRs. IC5supplies 5V (5M) to the control circuit, and IC9 supplies 5V(5C) to common circuits. IC6 supplies to the TX circuit, the RXcircuit and common circuits of needless save mode. Duringtransmission, 5TC becomes Low and Q3 is turned ON to supply5V (5T) to the TX circuit. During reception, 5RC becomes Lowand Q2 is turned ON to supply 5V (5R) to the RX Circuit.9. Optional Board TerminalTerminals for mounting the option board are provided atthe bottom edge of the TX-RX unit. The table below shows thecorrespondence between the board and terminals. R37, R69,R249, R258, R259, R304, R305 may have to be removeddepending on the type of option board being used.Name FunctionSB Battery (7.5V)GND GroundTXD Serial dataRXD Serial dataSQ Busy: highLOK Link acquired : low (TX mode)DI/ANI Modulation (ANI) inputDEO Detect outputTXAI/MUTE Modulation output from board or mic mute: lowTXAO Modulation input to boardRXAI Received signal input to boardRXAO Received signal output from boardD1 Binary 1D2 Binary 2OPT Scramble, Emergency:lowPTTIN PTT switch signal input to board (TX:low)5CNS Battery (5V)DI9 9600 bps data outputRXEMAO Received signal output from board (after de-emphasis)RXEMAI Received signal input to board (after de-emphasis)PTTOUT PTT switch signal output from board (TX:low)MONI Busy:lowLAMP Busy:lowAAC Audio Amp Control signal output from board(Busy:high)Audio Beep Beep signal output from board.AUX TXD Serial dataAUX RXD Serial data/Option switch port./EXT SWTable 1 Terminal name and functionFig. 15 Power supply circuitDisplay unitQ25RC5TC5R5T5CNSIC6IC9IC5Q3RF power amp (IC100)+BF1SBON/OFFVOL5M5C