Kenwood R-2000 Service Manual

Also see for R-2000: Instruction manual Service manual Service manual Service manual Service manual

R-2000CIRCUIT DESCRIPTION4} Third local oscillator (L03}This circuit consists ofPLLIC2:MN6147Cwhich in-corprates a 5kHzPLLand mixer. OneVCO isprovid-ed; the frequency rangeis39.505,...,44.500MHzand the dividing ratio rangeis7901,..,8900.ThisPLLcircuit is composed ofVCOQ 11: 2SC 1923,PLLIC2:MN6147 C and a loop filter consisting of08,09and010:2SC 1775. TheVCOoutputisbuffered(012},divided1/100to395.05,..,455.00kHz byIC3: MN54459L, buffered(013)and mixed with the9 MHz reference signal by IC4:SN16913Pto obtainthe9.39505,..,9.445 MHz third local oscillator fre-quency. Thisisfiltered(CF1)and amplified(Q15},then sent to the Receiver unit.5) Unlock mutingThe output fromPLLIC2 pin 2 (unlock) becomesanunlock signal through IC21:TA7324Pand071.andisused to control the audio muting circuit on Switchunit "B'' to reduce or eliminate any pulse noise whichmaybegenerated when the frequencyischanged andthePLLmomentarily resets.2. Control unitEN1EN2IC9Q)IC9@IC9©IC9@1}Rotary encoder input circuitOn the Encoder unit, a50slit rotary disc and 2 pho-tointerruptors generate 2 clock signals having a 90°phase difference; which are input to the Control unitvia theEN1 and EN2 lines. These clock signalsarewaveform shaped by IC6, quadrupledbythe gate cir-cuit consisting of IC7 and 8 (the50pulse/rev signalischanged to a200pulse/rev signal), and appliedIC12,through Flip-Flop IC9 1/4to the microprocessor pinNo.39(T1port). At the same time, the encoder's rota-tional dirctionisdetected from the clock pulses by theFFcircuit IC91/4andisinput to microprocessor pin29(Port 37). The waveforms at each point are shownin Fig.1.Encoder rotates for Rotates for Down.-Upoperation-1--Operation -Encoder output 1E neederoutput2IC7.8Gate outputUP/DOWN signalMicrocomputerT1 inputFig. 1 Encoder output to micro-processorinput timing and waveforms2) Program scan circuitIC10on the Control circuitisanastable multivibratorcircuit controlled by thePG.SCANswitch. Both itsoutput, and the clock signalareapplied to the micro-processor T 1 port.During scan, the multivibrator oscillators output pulsetrain is accessed by!Cs9 1/4,101/4and111/2,while the oscillator stopsinthe HOLD mode and onlythe Encoder clock pulseisavailable.The oscillator frequencyisdetermined by C 17 3,C 174. R145andVR1.When the tuning speedisSLOW or MID, the oscillator frequencyisapproximate-ly10,..,18Hz.When itisFAST.034turns on andthe oscillator frequencyisapproximately 5,...,9Hz.3} Clock circuitA 1 kHz clock signalisoutput fromPLLIC2(pin6),waveform shapedbyIC17 1/4and applied to the mi-croprocessor INT port (pinNo.6) to count the time.When the HOUR and MINUTE switches are de-pressed simultaneously the time display shows00:00.InCLOCK 1 mode, the time display stopsflashing and the clock begins counting the seconds(which are not shown} when the switches are de-pressed. When the displayisflashing, the HOUR andMINUTE switches cannotbeused to set the time.When the Function switchisset to any position otherthan FREQUENCY, depressing theHOURswitch willincrement the HOUR digit by one. When the HOURswitchisheldON,the Hours digit increases contin-uously. The Minutes digit does not change duringHOURS set.Each time the MINUTE switchisdepressed. the Min-utes digit increases by one. When the switchisheldON,the Minutes digit advances. The Hours digit doesnot change during Minutes set.Toprogram the timer, set the timerONtime and placethe timer switchON.Receiver power remains off untilthe timer preset timeisreached, when the relayisactivated and the power is switchedon.When the timerOFFtimeisprogrammed, the poweristurned off at that preset time. When the timer switchis ON, the power switch is inoperative.Thetimer relayoutput is available at the Remote control terminals onthe rear panel.4) Microprocessor power supply circuitWhen the microprocessor IC12: μPD80C49C1sinoperation, 5V should be applied to Vee pinNo.40.When the microprocessoris in the back-up standbymode, 2V should be applied. When the power switchisturned off,035and036change the level of RES!:Tpin No. 4 to low to protect the RAM, the VDDpin No.26becomes low to stop the oscillator and the con-tents of the RAM are maintained by the low standbyvoltage(Vee).·When the poweristurned on, 5V is applied to the Veepin. the VDDpin becomes high while theRESETpin isheld low to activate the oscillator, then theRESETpinreturns to a logic high and the program is reset.Oscillator stop Oscillator starts::DET="q.~·-Stai)mzed oscillating-----penodFig. 2 Micro-processor power supply circuit5