Kenwood TS-950S Service Manual

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

TS-950S/SD12CIRCUITDESCRIPTIONThe main received signal passes through bufferamplifier Q12 (2SK520) and a low-pass filter and isthen mixed with the VCO signal in the first mixer O13to Q16 (2SK520). The output is converted into the firstIF signal of 73.05 MHz. This signal is applied to the !Funit (X48-3060-00) from the MIF termina! (CN6) and isseparated into two seperate channels. One of thechannels passes through the buffer amplifier Q23(2SC2714) and is combined with the HET signal (64.22MHz) in mixer Q24 (3SK131) to generate an 8.83-MHzwide-band signal. This signal is routed from the rear asIF OUT1, and is used as a signal for the panoramicdisplay section of the SM-230 station monitor. Theother signal passes through buffer amplifier Q44(2SK520). Undesireable signal components are elimi-nated from the signal when it passes through theMonolithic Crystal Filter (MCF) XF2 with a bandwidthof 15-kHz. The signal is then applied to the secondmixer Q15 and Q16 (2SK520), mixed with the HETsignal (64.22 MHz), and converted into the second IFsignal (8.83 MHz). This signal is also separated intotwo channels: one is supplied to the noise blanker onthe AF unit (X49-3020-00}, and the other is applied tothe second |F signal filter circuit via the noise blankergate composed of diodes D5 to D8 (RLS135).This filter circuit utlizes wide-band LC filters L28 andL29, a 6kHz MCE, and a 2.7-kHz MCF (XF3.) The filtercircuit permits the use of several optional filters (1.8-kHz and 500-Hz or 250-Hz). (The TS-950SD has thesefilters included as standard equipment.) These filterscan be selected from the front panel via IC8 (TC9174F)of the signal unit (X57-3380-00).Thereceivedsigna!fromthesecondIFfilter,isappliedtothethirdmixerQ19andQ20(8SK131)whereitismixedwith theHETsignal(9.285MHz}. There-sulting signalisthenconvertedtothethirdIFsignal(455 kHz)andisroutedtothesignalunitviatheTR455terminal(CN17).This455-kHzsignalisthenseparatedintotwochan-nels,FMandnon-FM.InFM,thesignalisamplifiedby Q1 (3SK131)andappliedtothethirdIFfiltercircuit.Thisfiltercircuit utilizes a6-kHzceramicfilter(CF1)and 2.7-kHzceramic(crystal fortheTS-950SD)filter(CF101}.Twooptionalfiltersareavailableforthiscircuit;a500-Hzanda250-Hz.(TheTheTS-950SDtype hasthesefiltersincludedasstandardequipment.)Thesefilters, likethefiltersforthesecondIF,maybeselected fromthefrontpane!underthe controlof IC8.FOR SERVICE MANUALSCONTACT:MAURITRON TECHNICAL SERVICESwww. mauritron.co.ukTEL: 01844 - 351694FAX: 01844 - 352554Filter 2nd iF filter 3rd IF filterMode 8.83-MHz 455-kHzNon-FM All filters (including LC filter) Excluding 12 kHzFM No display {LC filter) only 12 kHz or 6 kHzTable 5 Selection of filters by mode (option)Filter 8.83-MHz 455-kKHzModeSSB, CW, FSK 2.7-kHz 2.7-kHzAM 6-kHz 6-kHzFM - (LC filter) 12-kHzTable 6 Initial settingi Display S type SD type8.83 |- © ILC filter} Ole}MHz |6 KHz © (MCE :L71-0266-05) 10 le}2. TKHZ © (MCF :L71-0222-05) iOle}1.8 kHz A {Not sold now) [4 (el500 Hz* AS (Crystal : YK-88C-1) 0 (e}270 Hz* A {Not sold now) x455 |12 kHz (FM only) | © (Ceramic : 172-0315-05} |O (-}kHz | 6 kHz © (Ceramic : 172-0319-05} |O (<}2.7 kHz © (Ceramic : L72-0333-05} | © (Crystal : YG-455S-1)500 Hz A (Crystal : YG-455C-1] O {ee}250 Hz A {Crystal : TG-455CN-1} Ole}* : Only one of them is selectable. © : Standard4: OptionX : Not availableTabie 7 Filters by typeThe 455-kHzsignalfromthethirdIFfilterisampli-fiedbyQ2(3SK131), andismixedwiththeCARsignal(355 kHz}inthefourthreceivemixerQ3(3SK131).Thesignalisconvertedintothe fourthIFsignalof100 kHz,andpassesthroughthenotchfiltercircuit,andisthenappliedto4(3SK131}.Theamplified output fromO4becomestheAFsignalafterpassing throughtheSSB/CWdetector,andisappliedtotheSCAFterminal(CN7).TheoutputofQ2isappliedtoQ22(2SC2712),tobecomethesquelchsignalfornon-FMreceivemodesbycomparator!C2(NJM2903M).TheoutputofQ4isalsoappliedtoQ10(2SC2712)toproducetheAuto-matic Gain ControlAGCsignal.IntheFMmode,the455-kHzsigna!passes throughIFbuffer amplifierQ28(2SC2712),andisappliedtothethird IFcircuit.Eitherwide-bandfilterCF2,fora12-kHz bandwidth,ornarrow-bandfilterCF3,fora6-KHzbandwidth,maybe selected.The outputisamplifiedbylimiteramplifiers IC6andIC7(wPC577H),and thenFM-detectedby ceramicdiscriminator CF4.Thenoisecomponents,atapproximately40kHz,areeliminated fromtheFMdetectoroutput,andasquelchcircuitconsistingofnoise amplifierQ19andQ20(2$C2712) andcomparator|C2{b/2)producesanFMsquelchcontrolsignal.