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Is this jumper on a 9090 driver board stock?

Discussion in 'Exclusively Sansui' started by Robisme, Nov 13, 2017.

  1. Robisme

    Robisme Sansui Enthusiast Subscriber

    Messages:
    11,793
    Location:
    Martinez California
    I don't remember seeing this before, and the last 9090 I did had the fuses on the driver board like this one.

    Any ideas?

    Thanks.

    upload_2017-11-13_20-54-45.jpeg

    Rob
     

     

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  2. Hipocrates

    Hipocrates Anti-Muppet Subscriber

    Messages:
    1,797
    Location:
    Costa Rica
    Not present on mine.
    That's weird.
     
  3. Robisme

    Robisme Sansui Enthusiast Subscriber

    Messages:
    11,793
    Location:
    Martinez California
    Thanks for checking. It is weird.

    Rob
     
  4. Hipocrates

    Hipocrates Anti-Muppet Subscriber

    Messages:
    1,797
    Location:
    Costa Rica
    I'm trying to see what it does, but I'm too dumb for that.
    Capture.PNG
     
  5. I LIKE MUSIC

    I LIKE MUSIC Super Member

    If my copy of the schematic is correct, the jumper is connecting terminals 7/8 and 11/12 of the edge connector together.

    This is the location of the jumper in red. See the edge connector terminals circled in blue.

    upload_2017-11-14_1-3-43.png




    And on the schematic. Red circles, edge connections 7/8 and 11/12. Blue circles show that they grounds.

    upload_2017-11-14_0-53-27.png

    In general (not necessarily specific to this board) this is done to reduce differential ground currents (ground loops) or if there is an issue with the edge connector or its wiring.

    I have not been inside one of these in a long time.
     
  6. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    I am inclined to think that the jumper may be have been added to cover up for a poor ground connection, maybe at the board edge connector. If ground connections have been separated like this it is for a reason, usually in favour of a 'star ground' somewhere else.
     

     

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  7. tnsilver

    tnsilver AK Subscriber Subscriber

    Messages:
    2,999
    Location:
    Boston
    It's ground and the jumper is stock. Here's a pic of one of my spare driver amps. Haven't checked in years, but I'm pretty sure the one in my unit is the same.

    [​IMG]
     
    Hipocrates and Hyperion like this.
  8. ManyMoonsAudio

    ManyMoonsAudio AKA paul79 Sponsor Subscriber

    Messages:
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    Location:
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    Yes, it is present on most of the 9090's I have worked on.
     
    Hipocrates likes this.
  9. The Fuxtor

    The Fuxtor AK Subscriber Subscriber

    Messages:
    2,817
    Location:
    Calgary, Alberta
    It's on mine too
     
  10. Robisme

    Robisme Sansui Enthusiast Subscriber

    Messages:
    11,793
    Location:
    Martinez California
    Good news. Thank you all.

    Rob
     
  11. LBPete

    LBPete Rolling Along Subscriber

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    Location:
    Long Beach, CA
    One more variation to the 9090/8080 driver board.

    - Pete
     

     

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