Leestereo's Restoration/Upgrade of a Sansui AU-555A

Discussion in 'Exclusively Sansui' started by Leestereo, Mar 30, 2018.

  1. playittwice

    playittwice Well-Known Member

    Messages:
    615
    Location:
    Dubuque Iowa
    As stated earlier, beautiful job and awesome write-up. It’s awe-inspiring and gives much motivation to re-store these fine pieces of vintage gear.

    Thanks.
     
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  2. The Fuxtor

    The Fuxtor AK Subscriber Subscriber

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    2,470
    Location:
    Calgary, Alberta
    Incredible write up..... Amazing job
     
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  3. slimecity

    slimecity Super Member

    Messages:
    2,520
    Location:
    New Zealand
    Nice, great to see you solved this. I had a 6500 and after replacing all caps and some electros with poly types, and even after putting in some newer low-noise transistors, I still couldnt address this in my unit.
     
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  4. patfont

    patfont AK Subscriber Subscriber

    Messages:
    2,797
    Location:
    South Jersey
    Ben as usual your work sets the standard, beautiful work. And doing this myself I can see the care you take even in component installation, all board fitted and sitting pretty.

    Question: When I do 555/505's I replace all the transistors on the amp board not just if it has the UFO's-it lowers the noise floor. When I do this I need to up the bias trimmer to 2K ohm. So the 850 Ohm would not be a match for me, can't see if you replaced all your transistors from the pic?
     
  5. Leestereo

    Leestereo Super Member

    Messages:
    2,040
    Location:
    Ottawa, ON
    For this 555A, on the main amplifier board, only the failure-prone 2SA726 transistors (TR801/TR802) were replaced. If you implement the mod, I think that with a 2kohm trimmer installed, you can keep the stock 1.2kohm resistors.
     
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  6. patfont

    patfont AK Subscriber Subscriber

    Messages:
    2,797
    Location:
    South Jersey
    Yes, sounds about right, because they just miss with the 1K trimmers.
     

     

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  7. stereofun

    stereofun Super Member

    Messages:
    1,204
    Location:
    Tucson, AZ
    Leestereo - your restorations will be visited for a very long time. As the next generation(s) restore these audio pieces - it is your documentation that will be considered one of the best sources :beerchug:
     
  8. afroaudio

    afroaudio Active Member

    Messages:
    153
    Location:
    Cape Town, South Africa
    Awesome documentation here Leestereo! To be referenced for years to come as stereofun said.. very keen to try the Baxandall mod, the 555A is voiced beautifully but tightening up that woolly bass will make it even better! thanks for the dedication
     
    Last edited: Jun 15, 2018 at 10:09 AM
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