Kenwood TS-950S Service Manual

Also see for TS-950S Digital: Instruction manual Instruction manual Instruction manual Instruction manual Service manual

TS-950S/SDCIRCUITDESCRIPTION2) ICprotectionThefinaltransistor collectorcurrentIsdetectedviathevoltagedropacrossR38ofthefinalunit.Sincethedetectedvoltageisnegative,itisinvertedandampli-fiedby1C8(NJM4558M)onthecontrolunit.IC8turnsonQ3(2SC2712), reducesthevoltageontheALCtimeconstantcircuit,anddecreasesthedrivetolimitthefinaltransistorcurrent.Whenthefuseonthefinalunitblows,the50-VAVRisturnedoff,TXIisgroundedbyD7 (MC921),Q15(DTA124ES),andQ14(DTC124ES),anddisablingtrans-mission.+TemperatureprotectionIfthefinalheatsinktemperaturerisestoapproxi-mately50°C,thetemperatureswitch(S1)ofthefinalunitturnson.Currentthen flowstothefanmotorthroughR23and05(1S1555), andR36andD10(UPZ4.7B), andthefanmotorStartsrunningatalowspeed.D10isazener diodethatproducesthe currentnecessaryforstarting themotor.{fthefinalheatsinktemperaturerisestoapproxi-mately70°C,temperatureswitch$2turnson,andD10andR36areshorted.Thevoitageappliedtothemotorthenincreases andthefanmotorrunsathigherspeed.Ifthesinktemperaturereaches 90°C throughsomefailure,S3turnson,TX!isgrounded,andtransmissionisdisabled.!fthepowertransformertemperaturerisestoap-proximately80°C,temperaturedetectionswitchS1oftheAVRunitturns onandthepowerisloweredtoprotectthetransformer,+Safetydischargecoolingcircuit70to80Visappliedtotheelectrolyticcapacitorofthepowersupplywheneverthepowerswitchisturnedon.Thiscapacitorwillnotdischargeimmediatelywhenthepowerswitchisturnedoff.Sincethevoltageonthe15-Vpowersupply soonfallswhenthepowersupplyisturnedoff,thevoltageremainingonthis ca-pacitorwillbeconsumedbythefanmotor.Thefallinvoitageonthe 15-Vpowersupplylineisdetected by D4 (MTZ4.7JC)onthefinal unit.ifthevoltagedropstoapproximately10V,Q11(DTC124ES)turnsoff,the collectorvoltagerises,andQ12(DTC1437S)turnson.WhenQ12turnson,Q13turnsonallowingthevoltagetodischarge slowlythroughR27,Q13,R26,D6keepingthe fan on.* Monitor circuit1) Modes other than FMThemonitorcircuitusesthesubreceivertoreceiveandmonitorthe signalsafterconversiontothetrans-missionfrequencyunlikeconventional monitorcircuitsthatmonitortheiFsignals.Thismonitorcircuitpro-ducesthesameaudiosignalthatistransmittedandmonitoredby anotherreceiver.(IntheAMmode,thesignalpassesthroughtheSSBfilterforproductdetec-tion.)ThesignaltakenfromthebandpassfilteroutputbeforeQ33oftheRFunitisappliedtothefirstmixer{Q8toQi1)ofthesubreceiverviaD49. Sincethelevelmightbetoo high,itisattenuatedbyQ37whenthesignalisdeterminedtobetoolarge,andisfurtherattenuatedbyQ4intheIFunit.Theamountofattenu-ationintheIF unitcanbe adjusted‘byVR1,andthedegreeofAGCcan alsobechanged.ThesubreceiveroutputSAFpasses throughIC6(c/4)andIC10{(d/4)oftheAFunit,andisappliedtoIC8{a/2)viathemonitorcontrol.Itisamplifiedandroutedinthesame mannerasansignal.Tocutoffnoiseenter-ingIC8whentransmissionsarenotmonitored,analogswitchIC6(b/4)isshortedtogrounduntilthemonitorcircuitisagainturnedon.2) FM modeThesignaloutput(pin2},havingpassedthroughtheclipperandpreemphasiscircuitintheFMmicrophoneamplifiercircuit(X59-3000-03),isappliedtothedeem-phasiscircuit.Theresultingsignalpasses throughIC10{c/4),appliedtotheC10(d/4)input(pin10),andisamplifiedandroutedasfortheothermodes.FOR SERVICE MANUALSCONTACT:MAURITRON TECHNICAL SERVICESwww, mauritron.co.ukTEL: 01844 - 351694FAX: 01844 - 35255421