Kenwood TS-950S Service Manual

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TS-950S/SDCIRCUIT DESCRIPTIONin 2-kHz steps. Division ratio data (N3) is provided bythe digital unit as data (29000 to 28001) which corre-sponds to 0.00 to 9.99 kHz. When the RIT and XIT areused, the division ratio changes so that the frequencyof oscillator VCO3 is shifted according to the setting ofthe RIT and XIT controls.The output from PLL3 is divided by 20 in IC3(M54459L), and is applied to pin 2 of IC4 (SN16813P)of MIX4. MIX4 combines the signal with the 10-MHzsignal. The resulting signal passes through the band-pass filter to obtain a signal of 12.9 to 12.8 MHz. It isthen applied to pin 2 of IC5 (SN16913P) of MIX3.PLL2 which is in the center of LO1: generates the49.5 to 44.6 MHz VCO2 signal. The 10-MHz referenceoscillator frequency (fREF) is applied to pin 5 of IC6(CX7925B)}, and is divided by 100 internally to producea 100-kHz comparison frequency. The output VCO2 isapplied to pin 5 of ICS of MIX3, where it is mixed withthe signal generated by PLL3. The resulting signalpasses through the bandpass filter to obtain a signal of36.6 to 31.7 MHz. This signal is then applied to ampli-fier Q3 (2$C2714), and then to pin 11 of IC6. Thissignal is divided by a value determined by N2, andcompared with the 100-kHz signal by the phase com-parator. The output frequency of MIX3 is locked in100-kHz steps. Divide ratio N2 is provided by thedigital unit as data (366 to 317) which corresponds to0.00 to 0.49 MHz and 0.50 to 0.99 MHz.The output from PLL2 is divided by 10 in IC7(MB467), and is applied to pin 2 of IC8 (SN16913P} ofMIX2. MIX2 combines the signal with the 40-MHzsignal. The resulting signal passes through the band-pass filter to generate a signal in the range of 35.05 to35.55 MHz. This signal is applied to buffer amplifierQ5 (25C2714), and is then routed to the AF unit.PLL1, which is upstream of LO1: generates the73.06 to 103.05 MHz VCO1 signal. It consists of fourVCOs, Q1 thru Q4 (2SK210x4). The 10-MHz referencefrequency (fREF) is applied to pin 5 of !1C11 (CXD1225M),and is divided by 20 internally to produce a 500-kHzcomparison frequency. The output from VCO1 isamplified by Q33 (2SC2714), and passes through thebandpass filter. One of the output signals is passedthrough buffer amplifier O37 (2SC2996) and directedto the RF unit. The other output is applied to pin § of{C12 (SN76514N) of MIX1. The signal is then mixedwith the signal generated by PLL2 and PLL3. Theresulting signal passes through the bandpass filter toproduce a signal in the range of 38 to 68 MHz. It thenpasses through buffer amplifiers Q34 and Q35(2SC2714x2) and is applied to pin 11 of IC114. Thissignal is divided by a value that is determined by N1internally, and compared with the 500-kHz signal bythe phase comparator. The output frequency fromMIX1 is locked in 500-kHz steps. Divide ratio N1 isprovided by the digital unit as data (76 to 136) whichcorresponds to 10 kHz to 30 MHz. One of the fourVCO1 signals is selected according to the VCO changedata supplied by the digital unit.The final output frequency of the main LO1 signal is73.06 to 103.05 MHz in 10-Hz steps, and depends onthe divide ratio data supplied by N1 to N3. This signalis supplied to the RF unit.+ Main LO2 (AF unit)In PLLO, Q1 (2SK508NV) of VCOO is used to gener-ate a signal of 64.22 MHz. The 10-MHz reference fre-quency (fREF) is applied to pin 5 of C13 (CXD1225M)},and is divided by 500 (2000 in FM mode) internally toproduce a 20-kHz (5-kKHz in FM mode) comparisonfrequency. The output from VCOO is applied to pin 11of 1C13, and is divided by 3211 (12844 in FM mode)internally. It is then compared with the 20-kHz (5-kHzin FM mode) reference signal by the phase comparatorto lock the VCOO frequency. Divide ratio data is sup-plied by the digital unit.The output from PLLO passes through buffer ampli-fier Q39 (25C2714) and a low-pass filter and is appliedto the IF unit as the main LO2 signal.¢ Main LO3 (CAR unit)n PLL6, VCO6 is used to generate a signal of ap-proximately 71.5 MHz. The 10-MHz reference fre-quency (fREF) is applied to pin 5 of 1C3 (CX7925B}, andis divided by 5000 internally to produce a 2-kHz com-parison frequency. The output from VCO6 is applied topin 11 of IC3, and is divided by a value determined byN6 internally, and compared to the 2-kHz referencesignal by the phase comparator in order to lock theVCO6 frequency. Divide ratio data N6 is provided bythe digital unit. The bandwidth is changed and thecarrier point is fine tuned by simultaneously changingthe division ratios (AN6 = A2N3) of PLL6 and PLL3 viamicroprocessor control.The output from PLL6 is divided by 100 internally in1C4 (M54459L) and applied to pin 2 of IC5 (SN16913P)of MIX7. in MIX7, it is combined with the 10-MHz ref-erence signal. The resulting signal passes through theceramic filter CF1 to obtain a signal of 9.285 MHz. Thesignal is further amplified by Q3 (2SC2714), and thenapplied to the IF unit as the main LO3 signal.+ Main LO4 (CAR unit)In PLL5, VCO5 generates a signal of approximately35.5 MHz. The 10-MHz reference frequency (fREF) isapplied to pin 5 of IC1 (CX7925B), and is divided by5000 internally to produce a 2-kHz comparison fre-quency. The output from VCOS is applied to pin 11 ofIC1, divided by a valued determined by N65 internally,and compared with the 2-kHz reference signal by thephase comparator to lock the VCO6 frequency. Divide-sion ratio data N5 is provided by the digital unit. The