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Trouble Shooting The First Stage Differential Amplifier

Discussion in 'General Audio Discussion' started by Spenser, Oct 13, 2018.

  1. Spenser

    Spenser AK Subscriber Subscriber

    Messages:
    446
    Location:
    Pittsburgh, PA, USA
    For this discussion, please refer to pages 39-43 of the below-linked

    TECHNICAL GUIDE FOR SERVICE
    TROUBLE SHOOTING METHOD
    O.C.L. MAIN AMPLIFIER CIRCUITS
    PIONEER
    SERVICE DEPARTMENT INTERNATIONAL DIVISION

    (Note: O.C.L acronym means -- love this -- Output Capacitor-Less.)
    Three questions:

    1. Is this a good practice for "...trouble shooting the the first stage differential amplifier..." that can be used with most, direct coupled push pull integrated power amplifiers? Right now I am thinking of it as pertains to a Pioneer SX-939 with a suspect, "long tailed pair."

    2. Is it necessary to disconnect the output transistors?

    3. What happens if you don't?

    Thanks!
    _____________________________________________

    http://www.kallhovde.com/pioneer/ocl-amp-techguide.pdf


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    Last edited: Oct 13, 2018
    awillia6 likes this.

     

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  2. dshoaf

    dshoaf That high voltage buzz Subscriber

    Messages:
    10,184
    Location:
    RIP 1954-2018
    This is a good example of the training Pioneer, sansui and many others provided for their dealers who signed up as a warranty repair station.

    The technical content is excellent and applies to mamy models beyond Pioneer.

    Lastly, to the question of removing the final stage devices, they carry the large currents. As the document states, by removing the final stafe devices, the amp will atill operate but up to about 1 watt output.

    Cheers,

    David
     

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