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Sansui 1000A biasing scheme

Discussion in 'Exclusively Sansui' started by gkargreen, Oct 9, 2018.

  1. gkargreen

    gkargreen Active Member

    Messages:
    459
    Location:
    Fairfax, VA
    I have added 10 ohm cathode resistors so that I can adjust the cathode current via the IBAMs that are a part of the g1 circuit and wondering what kind of value I should be seeing (voltage) across the 10 ohm resistors. Thanks!
     

     

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  2. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

    Messages:
    21,791
    Location:
    Glen Burnie Md.
    With 470-V to 480V on the plates you should see 32 to 33ma or so. That will give you around 15W to 15-1/4W per tube. Within the 80th percentile.

    Do the same thing for this as a Fisher, except the Sansui's plate Voltage is higher so the bias ma needs to be slightly lower to get the same wattage on the 7591's.
     
  3. gkargreen

    gkargreen Active Member

    Messages:
    459
    Location:
    Fairfax, VA
    Thanks again, Larry! I was thinking about the same, right now I am seeing around 18 ma on each of the tubes as measured across the newly installed cathode current resistors, so I guess I need to adjust the IBAMs on this set. BTW, this thing sounds amazing now that I have restored it, although until I got ALL the caps replaced (except for the 4-section can in the front) I was having balance problems. This receiver is probably one of the clearest-sounding tube pieces I have ever had on my bench!
     

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