Kenwood TS-950S Service Manual

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

TS-950S/SD26CIRCUIT DESCRIPTIONThrough the use of these circuits, when the SWR is3: 1 or more, the motor runs at high speed since theduty cycle of the motor drive voltage pulse is 100%.When the SWR is approximately 2 : 1, the duty cyclebecomes approximately 50%, and the motor runs atlow speed.The matching circuit used in the tuner is a T-type.The tap position from 1.8 to 30 MHz is controlled byeight relays, K101 to K108.Position detection potentiometers VR101 and VR102are linked to the rotation axes of variable capacitorsVC1 and VC2 with a gear ratio of 1: 1. Voltages of 0 to5 V (POD1 and POD2) are generated according to theposition of the variable capacitors. This position data isapplied to variable capacitor angle control comparatorsiC9 and IC10, and is used as the reference voltage inthe feedback control system which is used for presettuning and manual! tuning. The same signa! is alsodirected to the A/D converter of the digital unit, andused for preset data and to signal the completion oftuning.The potentiometer used here is not an control thatrotates 360 degrees. Since the rotation angle of thispotentiometer is limited, the rotation range is from theminimum capacity to the maximum capacity plus alittle extra for headroom.Through this control, like preset tuning, which willbe described later, POD1 and POD2 are monitored bythe microprocessor. If the lower {imit voltage of 0.6 Vor the upper limit voltage of 4.2 V is reached, themicroprocessor detects that the voltage is close to oneof its limits. To return the voltage to the opposite side,the APRE line is switched high. For VC1, if the voltageis close to the lower limit with respect to PRE1, thevoltage near the upper limit is output. !f the voltage isclose to the upper limit with respect to PRE1, thevoltage near the lower limit is output. The other vari-able capacitor VC2 outputs the voltage read by POD2to PRE2 as it is.If the variable capacitor voltage exceeds the speci-fied limit, itis returned to the opposite limit. The othervariable capacitor remains in the same position.2) Manual tuningWhenAUTO/MANUALselectswitchS62oftheswitchunit(A)(J/10)issettoMANU,thesignalappliedtoPRE1andPRE2isswitchedtothemanualtuningpotentiometersVR8andVR9viaanalog switchingIC,IC1.SimultaneouslyahighsignalisappliedtotheAPREline,causingQ3oftheATunittoturnon,andthecontrolswitchesofIC2andIC3areswitchedtoPRE1andPRE2.PotentiometersVR8andVRQgener-ateapproximately0.4to4.5 V,whichisappliedtoanotherinputofeachvariablecapacitor anglecontrolcomparator,ICQandC10,andiscomparedwiththepositiondata.Feedbackcontrolisperformedsothatthevoltages match.3) Preset tuningWhen auto or manual tuning ends (the OK signalchanges from high to low), and the voltage of POD1and POD2 is placed in memory as preset data for thatband by the microprocessor. When the band ischanged, even if tuning is performed in another band,VSWR and APRE go high, and preset tuning is per-formed by the feedback control system. !f the micro-processor detects that PRE? and PRE2 match POD1and POO2, the VSWR returns to its original value (thelast SWR value calculated}, and APRE goes low. Theauto control system becomes effective. (The initialpreset data when the microprocessor is reset includesstandard data for a 50Q toad on each band.)FOReeMANUALSCT:MAURITRON|TECHNICALSERVICESwww.mauritron.co.ukTEL:01844-351694FAX:01844-352554