Kenwood TK-860G Service Manual

Also see for TK-860G series: Instruction manual Instruction manual Service manual supplement Service manual Service manual

Contents

27TK-860G/862G APC CircuitThe automatic transmission power control (APC) circuitdetects part of a power module output with a diode (D35,D36) and applies a voltage to IC15. IC15 compares the APCcontrol voltage (PC) generated by the D/A converter (IC6)and DC amplifier (IC7) with the detection output voltage tocontrol Q31 and Q32, generates DB voltage from B voltage,and stabilizes transmission output.The APC circuit is configured to protect over current ofthe power module due to fluctuations of the load at the an-tenna end and to stabilize transmission output at voltageand temperature variations. Memory CircuitThe transceiver has a 2M-bit (256k x 8) flash ROM(IC501) and an 8k-bit EEPROM (IC505). The flash ROM con-tains firmware programs, data and user data which is pro-grammed with the FPU. The EEPROM contains adjustmentdata. The CPU (IC502) controls the flash ROM through anexternal address bus and an external data bus. The CPUcontrols the EEPROM through two serial data lines.Control CircuitThe CPU carries out the following tasks:1) Controls the shift register (IC9, IC510) AF MUTE, WIDE/NARROW, T/R KEY outputs.2) Adjusts the AF signal level of the audio processor (IC508)and turns the filter select compounder on or off.3) Controls the DTMF decoder (IC511).4) Controls the LCD assembly display data.5) Controls the PLL (IC3).6) Controls the D/A converter (IC6) and adjusts the volume,modulation and transmission power.Fig. 9 APC circuitFig. 10 Control circuit Display CircuitThe CPU (IC502) controls the shift register (IC510) anddisplay LEDs. When the LED1 line goes high when thetransceiver is busy, Q508 turns on and the green LED onD521 lights. In transmit mode, the LED0 line goes high,Q504 turns on and the red light lights. Backlighting LEDs forthe key operation unit (D509~D514) and LCD are provided.When the MBL line goes high, Q506 turns on, then Q505turns on, and the key illumination LED lights. A voltage isapplied to the MBL line to turn on the LCD backlight.Fig. 11 Memory circuitCIRCUIT DESCRIPTIONRFAMPQ22,25RFAMPQ27POWERAMPIC400APCDRIVERQ32DB+BQ31PRIDRIVERDCAMPIC7ANTSWD30LPFANTPOWERDETD35,36IC15APCCONTROLD16PCIC623pinQ33TEMPPROTECTIC6D/AconverterIC3PLLIC9ShiftregisterIC510ShiftregisterOELCDCSCNTCKCNTDTAFCLRAFMSKEAFSTBIC508AudioprocessorIC511DTMFDECO.IC502CPUTX-RX UNITLCD ASSYAFREG2AFREG1DTMDATDTMCLKDTMSTDDASTPLSTPLDTPLCKSCLSDAIC502CPUADDRESS BUSDATA BUSIC501FLASHROMIC505EEPROMQ506SWQ508SWQ504SWQ505SWMBLLED1LED0IC510ShiftregisterD521GRNREDD509~514MBLMBL Key Matrix CircuitThe TK-860G/862G front panel has function keys. Eachof them is connected to a cross point of a matrix of the KIN0to KOUT2 ports of the microprocessor. The KOUT0 toKOUT2 ports are always high, while the KIN0 to KIN2 portsare always low.The microprocessor monitors the status of the KIN0 toKOUT2 ports. If the state of one of the ports changes, themicroprocessor assumes that the key at the matrix pointcorresponding to that port has been pressed.IC502CPUKIN0KIN1KIN2KOUT0KOUT1KOUT2D/A GRPDNCHDNCHUPGRPUPAVOLDN VOLUPFig. 12 Display circuitFig. 13 Key matrix circuit