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Ref: SU-V4A service manual needed

Discussion in 'Electronic Repair' started by er, Sep 27, 2004.

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  1. er

    er Guest

    Hallo JVC dude,

    The failure is a strange background of a sort of "white noise" on one
    channel only after, say, 30 sec. after power on. The sound is OK apart
    from this noise.

    Originally there was a faulty protective IC SVITA7317P which I
    I wonder if we are looking at the same schematics because I can't find
    the references you mentioned for the transistor.

    Is there a way to test the driver stages, after removing the final
    power IC, so I can investigate the circuit? What should I put as a
    load on pins 14 and 16?

    Any other suggestions?

    Thanks a lot for you help.
  2. JVC dude

    JVC dude Guest

    Hi I was presuming the model I know as the SUV4X, a uk version , would
    be the same. Perhaps it isn't.
    Perhaps the refs are Q601/2/3/4 I haven't looked into my circuit yet.
    As for the fault, a crackle/hiss is usually a noisy tr or IC. some can be
    eliminated by swapping channel.
    I wouldn't normally run it without the power IC, the 'computer drive' may
    not operate correctly
  3. er

    er Guest

    Hallo AW,

    1) In my schematic diagram all the driver Qs are numbered as Q3xx for
    both channels. Anyway, I think you are referring to the transistors on
    the differential stages. Is that right?
    The input stage is made with a differential amplifier realized with a
    dual JFET
    on one package ( 2SK109).

    2) How can I realize in details this channel swapping you mentioned?
    Can you explain?

    3) In fact you are right. All the input circuitry is not working
    properly without the final stage, so it is almost impossible to check
    the circuit. Do you think what is needed are the transistors on the
    input stage of the power IC to create the correct bias voltages ( and

    Thanks for your time.

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