Kenwood TS-990S Service Manual

Also see for SP-990: Instruction manual

Contents

TS-990S29CIRCUIT DESCRIPTIONFig. 30 From the IF input stage to the SCIF (3rd IF)SC08M ATT: 0dBSC11SSC73SPLLDDSSCREFATT: -10dBATT: -20dBATT: -30dBATTATTATTATTPLLDDSMCFDDSSFIC6-4. From the IF Amplifier (SCIF2_AMP) to the 3rdMixer (SCMIX3) OutputIn the 3rd mixer (SCMIX3), the signal is down convertedby the SCLO3, and converted to the 3rd IF (SCIF3: 24kHz).6-5. From the 3rd Mixer (SCMIX3) to the SCIFThe 3rd IF (SCIF3: 24kHz) is amplified by the OP ampli-fi er (IC9) and sent to the control unit (X53-452) as SCIF.6-6. SCREFThe scope unit has equipped two PLL and three DDS,and it receives a 40MHz reference signal as SCREF fromthe PLL (MAIN) unit (X50-322) in order to distribute approxi-mately 8.4MHz reference signal to PLL (IC4, IC6) throughDDS (IC1, IC2).After this 40MHz reference signal passes buffer amplifier,it is distributed to three DDS as master clock.Approximately 8.4MHz reference signal generatedby DDS is inputted into each PLL of SCLO1 and SCLO2through a ceramic filter. The signal for SCLO3 use is con-ver ted into 10.676MHz by the DDS and becomes theSCLO3 signal via the amplifi er and fi lter.6-7. PLL to SCLO1/SCLO2■ SCLO1The VCO consists of components including the induc-tor (L60) and variable capacitance diode (D15). The PLL(IC4) is in control of this VCO for the SCLO1 use. The VCOoutputs different oscillation frequencies (64.847MHz and61.721MHz) for main signal reception and sub signal recep-tion.■ SCLO2The VCO consists of components including the inductor(L85) and variable capacitance diode (D23). The PLL (IC6)is in control of this VCO for the SCLO2 use. This oscillationfrequency (83.795MHz) is changed by ±250kHz to performscope sweeping. It is performed every 10kHz by dividing thebandwidth.Fig. 31 MCF adjustmentL79XF1L75CN10From 1st Mixer10.7MHzTune connectorCN12To 3rd MixerTune connectorQ44,45Supply 8V6-3. MCF AdjustmentThe MCF (XF1) is prepared for the 2nd IF frequency(10.7MHz). Since the MCF terminal impedance is 1 k, theimpedance is converted using variable inductors. The MCFis a filter that consists of a 2-pole MCF with a center fre-quency of 10.7MHz and a passband width of 15kHz.Connect an appropriate device, such as a tracking gen-erator, to the MCF adjustment connectors (CN10 and CN12)and turn the variable inductors to adjust the MCF. Make theMCF adjustments while in adjustment mode if you havereplaced the MCF (XF1), variable inductors, or scope unit(X42-343 A/10). When adjusting the MCF, apply 8 V (8 A) tothe scope unit.