Kenwood TK-940 service manual LCD Assembly, Cpu, Power switch circuit, Tone generator

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CIRCUIT DESCRIPTION

1)'7.LCD Assembly

The LCD assembiy consists of CPU, LCD, power switch circuit, and tone generator.

7-1. CPU

The CPU (IC2) carrres out the f o l o w l n g main operatlons:

It sends onloff data serially to the control unit from the AF volume control, LIPIDOWN key, system UP/ DOWN key, group UPIDOWN key, SCAlV key, and AUX key. It receives serial data from the control unit and displays it on the LCD.

The LCD can indicate alphanumeric characters (13 segments, 8 d~gits),TX, BUSY, CALL, SCAN, Talk- around, Option, AUX, TEL, and Delete.

7-2.Power switch circuit

Each time the power key IS pressed, a pulse IS sent t o the TX-RX unlt to turn the transceiver on or off.

7-3. Tone generator

The beeps and alert tones are generated by combining square wave signals of about 700Hz, 900Hz, and 1500Hz generated by the CPU These signals are output from pins 46, 47, and 48 of the CPU (IC2).The signals are rectified by a CR network and fed to the TX-RX unit LCD assembly and the de-emphasis circuit of IC9 (212).

Fig. 10 Tone generator circuit

Image 33

Contents FX-R%~?ONIT1x57-4590-XXI BIZ $@$, ~\, !? .- $LU~CO .i@&4170-XXGeneral TestingInstallation Planning Control Stations 5-1. Antenna system DC Power and wiringAntenna RadioSystem SET-UP Operating Features Scan indicator Front Panel Displays and Indicators System displayDelete 1 indicator Busy indicatorDetails of Features TEL ID Codes TEL Mode Time-Out TimerSystemIGroup Revert Last call revertSystem Search Free System RingbackTranspond Preferred System RevertAuto TEL Delay toneAudible User Feedback Tones Proceed toneCall indicator, alert tone Transmit disable receive-only channelsConventional System Operation Talk-aroundNon-continuous Horn AlertContinuous System Scan Type Fix system scanTransceiver Programming Data Program ModeIr 4-1.lntroduction KPG-4 Description Optional PC programming interface cableDealer mode Clone Mode FigureDescription of Each Modes System keyVolume key Panel Tuning ModeGroup key Scan keyKDD-4assembly Installing the Signaling Unit KDD-4 Dtmf OptionInstalling the KDD-4 in the transceiver InstallationJumper setup charts Accessory Connection Cable KCT-19 OptionMonireset ON-HOOK OFF-HOOK JU2 JU3 JUJ Mute UrimuteGND Terminal functionR5 and R6 setup chart Connecting the KCT-18 to the transceiverIgnition Sense Cable KCT-18 Option Modifying the transceiverExternal Speaker Connection procedureKES-3 Option KES-4 OptionFitting the Control Panel Upside Down Page Page Page Page If unit RF unitMCF ANT AMP If System -AMPSP PLL MIC AMPAudio amplifier unit Squelch circuit Microphone amplifier Buff IRF AMP PLL Vcxo DET InvswControl unit Power supply circuit PLL data outputHorn control Power switch circuit LCD AssemblyCPU Tone generatorTerminal connection diagram Block diagramEeprom AT24C02NlOS12.7 TX-RX Unit IC201 Terminal connection diagram Terminal functionTest DEC DINMicroprocessor 78312AGF3563BE TX-RX Unit IC209 Microprocessor 75308BGK740BE9 LCD Assy IC2 CLK Output aTEST2 TEST1 Eeprom NJM78L05UADTA114EU--DC DTA114YULCD Assy B38-0731-05 Rating wattage Cc4riqKusa TK-940/941Insulating Tube ANT Cable Speaker 16 QHM 1W Micrqphqnb Tapttte Screw A T Head T a P T T I E Sciiewpannel Screw SETY4U Icpqwer Modulej .. Drive TX-RXW w w W W 1 W l Uuupi I P C X E D CU U P F U P FR c Hesbnatuh ES $j Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Pattern Page Foil side IC20E Dtci 14EU DTCI44EU Page Page Component side PC Board View ~ o h ~ o n esident Page TX-RX Unit TX-RX Section X57 4590 XX A/2 11 TK A1 PLL O w m o d +4- aLIE- - aIz23z= Page Ccrl--------ASSYDISPLAY S~ECTION838 Eqqzj