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Kenwood TS-700A Problem

Discussion in 'Radio Circuits, Repair & Performance' started by N4GKS, Oct 6, 2019.

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  1. N4GKS

    N4GKS Ham Member QRZ Page

    I have a TS-700A on my bench, it has no receive audio on FM mode. SSB works fine. In FM mode, testing with simplex, the S meter shows full deflection, with white noise in the speaker, but absolutely no modulation in the received audio.

    The RXF pin on the IF FM board shows a good amplitude signal when I send a test transmission from another radio on the frequency. It doesn’t get much further than there. One thing I noted was that the 10.245MHz crystal oscillator associated with Q3 doesn’t seem to be oscillating, at least according to my Tektronix 75MHz scope using AC coupling. I’ve replaced Q3 and X1.

    Can you recommend how to proceed?
  2. G4COE

    G4COE Ham Member QRZ Page

    What do you get at the FM detector output, there is a test point at R29 and if you have a scope what signal is there at the base of Q6 the detector input?

    Confirm Q7 is the oscillator NOT Q3 as you said, if this is the case check the voltages, there is a test point there on C5/R2 just that I can't decipher it, try it with C5 disconnected.

  3. N4GKS

    N4GKS Ham Member QRZ Page

    Radio was fixed after bad transistor was replaced. Thanks.

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