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About 2SC2071/2SA939 and 2SB649/2SD669

Discussion in 'Electronic Repair' started by KaLe, Aug 3, 2007.

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  1. KaLe

    KaLe Guest

    Please tell me, can I replace 2SC2071/2SA939 with 2SB649/2SD669?

    Those 2SC2071/2SA939 are working as pre-driver transistors in one old
    Sansui stereo receiver, and because I cant find it any more for buy (and
    I have found non-working one 2SC2071 and two 2SA939), I wish to replace
    all 2SC2071/2SA939 with this Hitachi 2SB649/2SD669. Can I do this, but
    the most important to me is keeping original Sansui sound.

    Comments are welcome!

  2. David Farber

    David Farber Guest

    According to my 1986 Transistor manual these are the ratings.


    250V Vcbo
    220V Vceo
    50ma Ic
    1 watt Pc
    Beta 150


    180V Vcbo
    120V Vceo
    1.5A Ic
    20W* Pc
    Beta 60-320


    -250V Vcbo
    -220V Vceo
    -50ma Ic
    1W Pc
    Beta 150


    -180V Vcbo
    -120V Vceo
    -1.5A Ic
    1W Pc
    Beta 60-320

    * I'm not quite sure how the 2SB649 is only rated at 1 watt while the 2SD669
    complement is rated at 20 watts. Also notice that these substitutes have a
    lower breakdown voltage than the originals.

    Good luck.
  3. KaLe

    KaLe Guest

    Dana Fri, 3 Aug 2007 14:33:57 -0700 na news grupi
    osoba pod imenom David Farber je napisala...
    Thank you for that information David. About collector power dissipation
    different between 2SB649 and the 2SD669; they are talking about two kind
    of Pc, one is normal Pc and one is Pc with mark * and notice Tc = 25
    degrees C, that Pc with * is 20 W, and Pc without * is 1 W.

    I do not need that high breakdown voltage, 180 Volts is quite enough,
    because they will work as predrivers in audio receiver Sansui G8000.
    But I am wondering about that big difference between collector current,
    2SC2071/2SA939 have only Ic 50mA and 2SB649/2SD669 have 1.5A, how big
    difference?!? Is it really good value, did you checked?

  4. Guest

    Tamb=25C vs Tcase = 25C wont explain that much difference. You dont
    use 20w trannies as drivers in a tr amp.

    Also your betas are different, 60 may be not enough.

    I wouldnt choose a 20w tr as a driver. It may well work tho.

  5. KaLe

    KaLe Guest

    Dana Sat, 04 Aug 2007 09:09:42 -0700 na news grupi
    osoba pod imenom je napisala...
    But in datasheet you can read two different values for Pc (collector
    power dissipation). First Pc data is really 1W and second Pc data has
    notice "Value at Tc=25" and that second Pc has 20W.
    No problem about that, beta is for my model with mark "C" from 100 -
    I wil not use them as drivers, I will use them as pre-drivers instead
    2SA818/2SC1628 or instead 2SA939/2SC2071.
    Please take a look at and you will see that
    G8000 has as drivers 2SA968/2SC2238.

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