Kenwood TS-950S Service Manual

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TS-950S/SD CIRCUIT DESCRIPTIONbandwidth is changed and the carrier point is finetuned by simultaneously changing the division ratios(AN5 = ~AN6) of PLL5 and PLL6 and (AN5 = A2N3) ofPLL5 and PLL3 via microprocessor control. The divi-sion ratios are shifted in CW mode as well.The output from PLLS5 is divided by 100 in 1C2(M54459L) to generate a 355-kHz signal. This signalpasses through buffer amplifier 01 (2SC2712), and isapplied to the signaling unit as the main LO4 signal.* Sub LO1 (PLL unit)in PLL8, downstream from LO1, VCO8 generates asignal from 109 to 107 MHz. The 10-MHz referencefrequency (fREF) is applied to pin 5 of IC10 (CX79258),and is divided by 5000 internally to produce a 2-kHzcomparison frequency. The output from VCO8 is ap-plied to pin 11 of C10, divided by a value determinedby N8 internally, and compared with the 2-kHz signalby the phase comparator locking the VCO8 frequencyin 2-kHz steps. Dividesion ratio data N3 is transmittedfrom the digital unit as data (54500 to 53501) whichcorresponds to 0.00 to 9.99 kHz. Since the sub re-ceiver section functions as a monitor circuit in thetransmit mode, the division ratio is changed so that theVCO8 oscillator frequency is shifted when XIT is used.The output from PLL8 is divided by 20 in IC11(M54459L), and is applied to pin 2 of IC12 (SN16913P)of MiX12. MIX12 combines the signal with the 20-MHz reference oscillator signal. The resulting signalpasses through a bandpass filter to obtain a signal of25.45 to 25.35 MHz. This signal! is divided by 10 in1C13 (MB467) and is applied to pin 2 of IC14 (SN16913P}of MIX11. MIX11 mixes the signal with the 10-MHzreference signal. The resulting signal passes througha bandpass filter to obtain a signal of 12.545 to 12.535MHz. This signal is applied to pin 2 of C15 (SN16913P)of MIX10. MIX10 mixes the signal with the 50. /5-MHzsignal from the sub LO2. The resulting signa! passesthrough a bandpass filter to obtain a signal of 38.205 to38.215 MHz. This signal is applied to pin 2 of IC16(SN16913P) of MIX9.In PLL7, which is upstream from LO1, VCO7 gener-ates a signal of from 40.065 to 70.055 MHz. It con-sists of four VCOs, Q1 thru O4 (2SK210x4). The 10-MHz reference frequency (fREF) is applied to pin 5 ofiC17 (CX7925B), and is divided by 1000 internally toproduce a 10-kHz comparison frequency. The outputfrom VCO7 is amplified by Q13 (28C2714), and passesthrough a bandpass filter. One of the outputs from thisfilter is applied to buffer amplifier Q14 (2SC2996) andis directed to the RF unit. The other output is appliedto pin 5 of IC16 of MIX9. Here the signal is mixed withthe signal generated by PLL8 and LO2 OSC2. Theresulting signal passes through a low-pass filter toproduce a signal of 1.86 to 31.85 MHz. It then passesthrough buffer amplifiers Q11 and Q12 (2S8C2712x2)and is applied to pin 13 of 1C17. This signal is dividedby a value determined by N7 internally, and is com-pared with the 10-kHz reference signal by the phasecomparator to lock the MIX9 output frequency in 10-kHz steps. Divide ratio data N7 is provided by thedigital unit as data (186 to 3185) corresponding to 10kHz to 30 MHz. The VCO change data of the fourVCO7 VCOQ’s is the same as that of VCO1. The A.LPFuses operational amplifier C18 (NJM4558SD) andswitches the loop constants A to D of VCO7.ThefinaloutputfrequencyofthesubLO1signalis40.065to70.005MHzin10-Hzsteps,anddependsonthedivideratiosN7andN8,andisappliedtotheRFunit.+ Sub LO2 (PLL unit)TheLO2localoscillatorsignalsaregeneratedbythe50.75-MHzcrystal oscillator(X1)andQ16{2SC2714).Onelocaloscillatorsigna!issenttothesubLO1 PLLloopandisappliedtopin5ofIC15ofMIX10.Theotherlocaloscillatorsignalpasses throughbufferam-plifierQ17(28C2714)andalow-passfilter,andisdi-rectedtotheIFunit asthesubLO2signal.LocaloscillatorsignalsgeneratedbythecrystaloscillatorcircuitareappliedtothePLLlooptocanceldrift.+ Main and sub CAR (CAR unit)inPLL4,VCO4generatesasignal ofapproximately69.5MHz.The10-MHzreferencefrequency(fREF)isappliedtopin5ofIC6(CX7925B),andisdividedby5000internallytoproducea2-kHzcomparisonfre-quency. TheoutputfromVCO4isappliedtopin11ofIC6,adividedbyavalueddeterminedbyN4internally,andcomparedwiththe2kHzsignalwithbyphasecomparatorlockingVCO4.DivideratiodataN4isprovided bythedigitalunit.Themodeofoperationischangedandthecarrierpointisfinetuned bysimulta-neouslychangingdivisionratios(AN4—S2N3)ofPLL4andPLL3anddivisionratios(AN4=A2N8)ofPLL4andPLL8withthemicroprocessor. Thedivisionratios arealso shiftedwhenthepitch controlischangedinCWmode.Oneoftheoutputs fromPLL4isdividedby100byIC7(M54459L)andappliedtopin2of IC8(SN16913P)ofMIX13.InMIX13,itiscombinedwiththe10-MHzreferencesignal.Theresulting signalpasses throughceramicfilterCF2togenerateasigna! of10.695MHzandthenpasses throughamplifierQ5(2SC2714),andisappliedtothe signalunit asthesubCAR.Theotheroutputisappliedtopin5ofC10(SN16913P)ofMIXSand usedas part ofthemainCAR.InPLL9,VCO9generatesasignal ofapproximately59.5MHz.The10-MHzreferencefrequency(fREF)isappliedtopin5of1C9(CX7925B), andisdividedby5000internallytoproducea2-kHzcomparisonfre-quency. The output fromVCO9isappliedtopin11ofIC9,dividedbyavaluedetermined byNg@ internally,andcomparedwith the2-kHzsignalinthephase com-