Kenwood TS-990S Service Manual

Also see for SP-990: Instruction manual

Contents

TS-990S27CIRCUIT DESCRIPTIONFig. 28 Antenna distribution diagramATFINALATSANT1 ANT2 ANT3 ANT4 RX(OUT) RX(IN)BPF etc.DividerLoss 3dBANT1 ANT2SANT1 SANT2 SANT3 SANT4ANT3 ANT4MRXIOSRXIO OFFOFFRXANTOFFOFFDIV1DIV2(X55-313 A/2 )X57-827( A/2)Main : ANT1; Sub : ANT1 (default settings)K801 K802 K803 K804K805 K806 K807 K808K17K18K19D19K10K12K14K15RX unitTX-RX unitK9Each relayshows anOFF state.The relays are OFF at the timeof transmission to preventthe imposing of high power.ANT switching relay:Used to switch themain reception andtransmission paths.Used to switch thepath if the subreceiver and mainreceiver do notshare the samepath.connect the antenna dedicated for reception through a relay(K10, K12, K14, K15, or K17).This model includes a current protection circuit. The cur-rent running in the final portion is converted into a potentialdifference between the ends of a 5 m resistor inserted intothe power supply line, and IC5 detects the potential differ-ence. When the potential difference is larger than a specifiedvalue, IC5 output activates the ALC protection function. ThisALC protection function is controlled so that the current doesnot exceed the predetermined value when the current at thefinal portion is increased for some unexpected reason. Otherprotection circuits include the same as those in previousmodels.Main: ANT1; Sub: ANT1 (default settings)ANT switching relay: Used to switch the main reception and transmission paths.Used to switch the path if the sub receiver and main receiver do not share the same path.Each relay shows an OFF state.The relays are OFF at the time of transmission to prevent the imposing of high power