WORKING replacements for Zetex ZTX transistors in ZX Spectrum? - Sinclair

This is a discussion on WORKING replacements for Zetex ZTX transistors in ZX Spectrum? - Sinclair ; Hello, I've just sort of given up on getting my hands on those hard-to-find ZTX transistors over here in Germany. Which other, available, types actually do work as a replacement? As you will know the Spectrum has ZTX650 (or TIPP31), ...

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Thread: WORKING replacements for Zetex ZTX transistors in ZX Spectrum?

  1. WORKING replacements for Zetex ZTX transistors in ZX Spectrum?

    Hello,

    I've just sort of given up on getting my hands on those hard-to-find ZTX
    transistors over here in Germany.

    Which other, available, types actually do work as a replacement?

    As you will know the Spectrum has ZTX650 (or TIPP31), ZTX450, ZTX313,
    ZTX213 and BC184 inside.

    Here's what I came up with, but this is pure theory. What I'd need is a
    confirmation which of these replacements actually do work in practice.
    Also what works for the ZTX313 as the BSV26 I came up with seems just as
    hard to get.

    ZTX650, possible replacements 2SC3328, 2SD1207, 2SD1835
    TIPP31, possible replacements MPS 650, 2SD1055, 2SD1227, 2SD1207
    ZTX213, equals BC 213, possible replacements BC 257, BC 307, BC 557
    ZTX313, equals BSV 26, replacements unknown
    ZTX450, possible replacements BC 337A, BC 637, BC 639, 2SD1207
    BC184, equals BC183, possible replacements BC 413/414, BC 550

    I'd be grateful for any help so that I can get this spectrum to fly
    again! At least the ZTX650 is definitively gone.

    (And please excuse my not so good English)
    --
    Linards Ticmanis

  2. Re: WORKING replacements for Zetex ZTX transistors in ZX Spectrum?

    Linards Ticmanis wrote:
    > Hello,
    >
    > I've just sort of given up on getting my hands on those hard-to-find ZTX
    > transistors over here in Germany.
    >
    > Which other, available, types actually do work as a replacement?
    >
    > As you will know the Spectrum has ZTX650 (or TIPP31), ZTX450, ZTX313,
    > ZTX213 and BC184 inside.
    >
    > Here's what I came up with, but this is pure theory. What I'd need is a
    > confirmation which of these replacements actually do work in practice.
    > Also what works for the ZTX313 as the BSV26 I came up with seems just as
    > hard to get.


    A transistor is a fairly simple device.
    There're only a few variables that would affect its suitability as a
    replacement... Those are...

    Medium: Determines the voltage they saturate at, silicon is 0.7 volts,
    germanium is 0.3, other substances have different characteristics.

    Polarity: (pnp can only replace pnp/npn only replace npn)

    Current load: This is a minimum of course, any transistor that matches or
    exceeds the current load of the one you're replacing should do, as long as
    it fulfills the other requirements...

    Switching speed: Only really a concern if it's part of a digital circuit or
    high quality audio amp or something. Most transistors have timing graphs in
    their specs anyway. But, the faster the better, as long as it's as fast or
    faster than the one you're replacing it'll work.

    package size: well, the transistor's got to fit in the space the one it's
    replacing vacates hasn't it?

    So, as long as you find an adequately sized NPN (or PNP) transistor capable
    of taking the current load of the original and capable of switching (if
    required) fast enough, it'll work.

    If it's just a power transistor that's part of the power supply you don't
    need to worry about switching, only medium, polarity, size and current load
    are important. Suppose there might also be a thermal range variable if
    you're going to drive the thing very hot...

    (NB: This is only for bipolar transistors... for FETs and MOSFETS, you've
    got other concerns)
    --
    | |What to do if you find yourself stuck in a crack|
    | spike1@freenet.co.uk |in the ground beneath a giant boulder, which you|
    | |can't move, with no hope of rescue. |
    | Andrew Halliwell BSc |Consider how lucky you are that life has been |
    | in |good to you so far... |
    | Computer Science | -The BOOK, Hitch-hiker's guide to the galaxy.|

  3. Re: WORKING replacements for Zetex ZTX transistors in ZX Spectrum?

    Andrew Halliwell wrote:

    > (NB: This is only for bipolar transistors... for FETs and MOSFETS, you've
    > got other concerns)


    And don't even start about Boba Fett.

    --
    Duncan Snowden.

  4. Re: WORKING replacements for Zetex ZTX transistors in ZX Spectrum?


    "Duncan Snowden" wrote in message
    news:4824d225$0$6431$834e42db@reader.greatnowhere. com...
    > Andrew Halliwell wrote:
    >
    >> (NB: This is only for bipolar transistors... for FETs and MOSFETS, you've
    >> got other concerns)

    >
    > And don't even start about Boba Fett.
    >
    > --
    > Duncan Snowden.



    Boba Fett? ... Boba Fett? ... Where? ...



  5. Re: WORKING replacements for Zetex ZTX transistors in ZX Spectrum?

    Hello,
    if I remember true, I put a 2N2369 in place of a ZTX313 long years ago
    in a simple video adaptation circuit that was designed for modifying a ZX81
    with normal (english) PAL signal to "near SECAM format" for connecting it
    to french TV receivers... It was working properly, so I imagine the ZTX313
    replacement by a 2N2369 was the right choice ? This was because it was
    already not possible to find ZTX313 in electronic shops in Paris 20 years
    ago...
    Alain-Pierre

    "Linards Ticmanis" a écrit dans le message de
    news:482409b2$0$6779$9b4e6d93@newsspool2.arcor-online.net...
    > Hello,
    >
    > I've just sort of given up on getting my hands on those hard-to-find ZTX
    > transistors over here in Germany.
    >
    > Which other, available, types actually do work as a replacement?
    >
    > As you will know the Spectrum has ZTX650 (or TIPP31), ZTX450, ZTX313,
    > ZTX213 and BC184 inside.
    >
    > Here's what I came up with, but this is pure theory. What I'd need is a
    > confirmation which of these replacements actually do work in practice.
    > Also what works for the ZTX313 as the BSV26 I came up with seems just as
    > hard to get.
    >
    > ZTX650, possible replacements 2SC3328, 2SD1207, 2SD1835
    > TIPP31, possible replacements MPS 650, 2SD1055, 2SD1227, 2SD1207
    > ZTX213, equals BC 213, possible replacements BC 257, BC 307, BC 557
    > ZTX313, equals BSV 26, replacements unknown
    > ZTX450, possible replacements BC 337A, BC 637, BC 639, 2SD1207
    > BC184, equals BC183, possible replacements BC 413/414, BC 550
    >
    > I'd be grateful for any help so that I can get this spectrum to fly
    > again! At least the ZTX650 is definitively gone.
    >
    > (And please excuse my not so good English)
    > --
    > Linards Ticmanis




  6. Re: WORKING replacements for Zetex ZTX transistors in ZX Spectrum?

    On Sat, 24 May 2008 22:31:42 UTC, "Alain-Pierre CHERTIER"
    wrote:

    > Hello,
    > if I remember true, I put a 2N2369 in place of a ZTX313 long years ago
    > in a simple video adaptation circuit that was designed for modifying a ZX81
    > with normal (english) PAL signal to "near SECAM format" for connecting it
    > to french TV receivers... It was working properly, so I imagine the ZTX313
    > replacement by a 2N2369 was the right choice ? This was because it was
    > already not possible to find ZTX313 in electronic shops in Paris 20 years
    > ago...
    > Alain-Pierre


    Reading a book from Adrian C. Dickens (Himself!!!), I see a
    troubleshooting section. WRT the power supply section, the book says
    that you can substitute the ZTX 213 (pnp) and the ZTX651 (npn) with a
    low power BJT.

    So, at least for the power supply section (-12 V), it seems that
    there's some equivalency...

    Mentore

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