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Cross Reference Please: NPN TO66 Case Transistor

Discussion in 'Electronic Repair' started by [email protected], Nov 13, 2007.

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  1. Guest

    Apparently made by Signetics, marked as follows:

    AMP2947
    6808

    I find no cross for it in my ECG book, can't find a direct reference
    on-line. This is the driver transistor for a vintage-1971 AR
    integrated amplifier. The outputs are 2N3055s.

    Their schematic lists in parenthesis (2N3054) which physically fits,
    but gives quite a distorted output. I matched two 2N3054s with very
    low leakage and matching Beta, got distortion. I used two "stock"
    transistors from another amp, worked just fine. Which, by the way,
    closely match on my tester the parameters of the 2N3054s... go
    figure.

    Thoughts? Ideas?

    Thanks in advance.

    Peter Wieck
    Wyncote, PA
     
  2. N Cook

    N Cook Guest

    if signetics then presumably 1968 , could it be Ge ?
     
  3. Guest

    Nope, all silicon per AR.

    Once upon a time a while back, Mouser crossed this to the 2N3054,
    which worked for me in some examples of this amp. But not this
    example. One person in another NG suggested that newer-run transistors
    are "faster" than older ones - perhaps I should add some small
    resistance - I will try that tonight.

    I think I may have a very-early-run AR amp so, we shall see.

    Peter Wieck
    Wyncote, PA
     
  4. Guest

    Thanks all for your ideas and responses. I did get a lead to a former
    AR Employee, Alex Barsotti who works now for AB Technical Services in
    Worcester, MA. He happens to have the exact replacements in-stock,
    can't ask for any better. Yes, there are some differences between it
    and the 2N3054, such that the more common unit *will* work some of the
    time, but not all of the time.

    I will try the added resistor trick before changing out those that are
    in there now, but as they are on sockets, even a change-out is the
    work of a few moments.

    Thank you, Bruce, Roy and finally Alex for getting involved in this
    tiny little request.

    Peter Wieck
    Wyncote, PA
     
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