Current Source replacement of 2SK34 in SX-780 PSU

Discussion in 'Pioneer Audio' started by RFmaster, Oct 26, 2015.

  1. rcs16

    rcs16 Super Member

    Messages:
    3,048
    Location:
    Baldwin, Ontario, Canada
    I do not buy that NTE is garbage, I have proof, I used TO-220 drivers in my Pioneer SX-950 20 years ago and they are still fine.
    but NTE parts should be used as a last resort since there are usually many cheaper/better options.
    for the jfet match Idss is one of the most important spec's in order to match a jfet. Pinchoff voltage is another. Since this application is basically DC abs max voltages and power dissipation are things to match. If you look at many Sansui high end gear, they used a simple bjt/diode/resistors as a constant current source for this linear regulator supply startup application..
    Echowars led/bjt CCS is another option.
     
  2. xconnectiv

    xconnectiv New Member

    Messages:
    2
    is this cucuit work with SX-1980 power supply ?
     
  3. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time Subscriber

    Messages:
    20,587
    Location:
    Bensenville,Illinois
    NO

    The sx-1980 has a MUCH higher voltage that calls for that specific EchoWars circuit, not a CRD or JFet.
    depending upon the transistor ratings, it can work and be safe at some insanely high voltages.
    The original (and individually selected) JFet from the factory was always in jeopardy, running on the ragged edge.
     

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