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Obsolete Parts

Discussion in 'Electronic Basics' started by phaeton, May 24, 2007.

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  1. phaeton

    phaeton Guest

    Not so much here (on Usenet (or more properly, the Google Groups
    Convenient Interface To Usenet)), but at times in electronics related
    IRC Channels, I hear periodic scoffing at various parts I'm using or
    have inventory of. Namely, things like the LM741, the 2N2222, maybe
    the TTL555, vacuum tubes and other 'old school' stuff that's been
    easily outdone several times over with replacements that are more
    reliable, more efficient, less noisy, cheaper, and all-round better in
    every way.

    True, there's a certain amount of silliness among some audiophiles and
    musicians (especially guitarists) when it comes to 'old
    equipment' (and I only say this because I'm guilty of it too), but I
    would expect this audience to be very fractional. (In a nutshell,
    guitar effects are often about polluting the otherwise good signal
    with *crap*, and other artifacts that result from the limitations of
    the devices or circuit).

    So why do they still make the 741, or the 2N2222? Or some of those
    old opamps that can latch up tight with the right or wrong input
    signal, never to return till the power is cut off? Are there still
    uses for these old designs that newer components won't accommodate?

    What's keeping them alive?

  2. Charles

    Charles Guest

    1/ Low cost
    2/ Habits (older designers still turning a trick or two)
    3/ Many suppliers
    4/ A plethora of application data and neat circuits
    5/ A form factor allowing experimentation ... one can hand-solder to them
  3. Eeyore

    Eeyore Guest

    Because ppl still buy them. That's the only reason ever.

    For some unchallenging applications a cheap 741 is doubtless quite fine although
    I'd expect it to be deprecated by now if only for unsatisfactory single-rail
    operation and high quiescent current consumption by modern standards.

    As for the 2N2222 do you mean the PN2222 ? The 2N2222 is in metal can (TO-18)
    and very expensive as a result.

    The PN2222 is in TO-92 and is just a general purpose npn silicon transsitor with
    fairly average specs. At least it's not pricey but more modern devices typically
    have loads more current gain which is usually a desirable parameter.

    I've never seen/noticed the 2222 suggested in European hobby sources byw.

  4. Don McKenzie

    Don McKenzie Guest

    That's because they have always used the BC families.
    I think a suitable replacement for the PN2222a is the BC547b.

    Someone will correct me if this number is wrong. :)

    However, you must swing the pinout 180 degrees for them to work.
    And yes, they still make mountains of the BC equivalent.


    Don McKenzie

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  5. Eeyore

    Eeyore Guest

    Pretty much. The 2N3904 etc family was popular once too for hobby stuff as were
    some of the Motorola 'house' devices.

    No, you got it right. The BC546/7/8/9/550 family do have lots more current gain
    though. Higher current gain seems to be associated with more modern devices.

    The pinout will be the same as a 2N2222. Most of the BCs have the same pinout as

    And even the Chinese use them.

  6. Don McKenzie

    Don McKenzie Guest

  7. Eeyore

    Eeyore Guest

    Our supplier used Philips parts for the BC5xx's. They're so multi-sourced I
    doubt anyone needs to market any 'dodgy' ones.

  8. phaeton

    phaeton Guest

    Actually Graham, I do mean the metal can 2N2222. I have about 20 of
    them on hand, and I frequently run into* circuits on the intarweb that
    spec them. I've also got tons of BC stuff, mostly from a Futurlec
    transistor assortment. These aren't spec'd so often, but I sometimes
    substitute them on the breadboard and they usually do fine. As I
    (might have) said before, I mainly do music-related audio stuff which
    is in the strange category of intentionally adding noise and
    disgruntlement to a perfectly good signal.


    (*) "frequently run into circuits"....... this is another discussion
    entirely (but wtf, i'm game), but I seem to notice that there is an
    MFT** of electronics tutorials, data sheets, and other info available
    on the web. Seems however, that probably 90% of it resides on pages
    that still say "last updated mm/dd/1997" or so. I don't know what
    happened in 1997, but this invaluable resource dried up about that
    time, leaving behind only relics that will someday die. Sad.

    (**) MFT == Metric FuckTon
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