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What Germanium PNP transistor do I use?

Discussion in 'Electronic Basics' started by [email protected], Mar 16, 2007.

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  1. Guest

    What Ger PNP transistors do I use for the following circuit in a
    radio: HF AMPLIFIER, MIXER; LF AMOPLIFIER, DRIVER and AUDIO OUTPUT?

    Does anyone know whether the numbers of the trasnsistors are
    standardized? Or each manufacturer use its own? It seems that there
    are tons of numbers out there such as 2N107, 2N239, 2S678, etc.......

    God Bless!

    Daniel
     
  2. You don't.

    Germanium transistors were pretty much obsoleted forty years ago, by
    silicon transistors. There is a far better range of silicon transistors,
    and generally they have far better specs than germanium transistors.

    The only reason you'd use a germanium transistor at this time is if
    there was a specific reason for using germanium. There are still some
    things where germanium transistors can be useful, which is why some
    are still being manufactured, but the average hobbyist wouldn't have
    need for those uses. And there is no reason to use germanium transistors
    in a radio.

    If you are looking for germanium tranistors because you have a schematic
    that uses them, and then you can't find the devices specified, it's because
    the schematic is decades old and you need to drop that schematic and
    find soemthing more modern, than try to find germanium transistors
    to use in the schematic.

    The reason some of us have germanium transistors lying around is because
    we accumualted them decades ago, when they were still common. Beyond
    taht, you'll have to go out of your way to get them.

    Michael
     
  3. ian field

    ian field Guest

    The OP might want to preserve originality while repairing an old radio,
    otherwise I'd select a fairly ordinary silicon PNP type and tweak the bias
    if necessary.
     
  4. Chris

    Chris Guest

    Hi, Daniel. I've got to assume you're working with an existing radio
    circuit, probably an older one made in the 1960s when germanium PNPs
    and negative supplies (positive GND) ruled the earth. Those were the
    days.

    Here's the drill. Find the standard JEDEC 2N number, either in the
    schematic or printed on the body/case of the transistor. Then go to
    this link:

    http://nte01.nteinc.com/nte/NTExRefSemiProd.nsf/$$Search?OpenForm

    and type in the manufacturer part number for the transistor. The NTE
    cross reference will probably work for you. NTE parts are available
    at many different places, including many TV/radio repair shops. You
    can also get these online at many places. You can go to their main
    page:

    http://nteinc.com/

    to find a distributor.

    Good luck
    Chris
     
  5. Joerg

    Joerg Guest

    That's right, unless it's hobby and there are tons of them in the box.
    My favorites were AC127 for audio, AF126 up to FM band, and AF239 for
    the really hot stuff.


    Where? Where? <drool>

    All I've found so far was new old stock so it can't be used in any new
    design. Ge would be really handy for very low voltage applications such
    as starter circuitry for a single fuel cell converter.

    And that accumulation habit has rescued my old Minolta camera where I
    really needed a Ge diode. The old OA91 works like a champ after being
    boxed up for about three decades.
     
  6. Meat Plow

    Meat Plow Guest

    I've repaired several old time transistor portables using germaniums
    scavaged over the years from all sorts of 60's portable crap. And that
    relates a lot with how I got my start with this stuff back in the
    60's. But I agree that if this is an experimental or kit that the OP needs
    to find something more current dated unless he's just into that kind of
    stuff.
     
  7. Guest

    Michael:
    Thanks for your education. But I have an old 4-transistor superhet.
    radio schematic and my kits
    want to build this radio. So I want to find out what Ge transistors I
    need. My radio
    knowledge is severely limited, but I know the first transistor is very
    different from the
    last two (a pair) that do the audio output job.

    Best! Daniel
     
  8. Guest

    Thanks, Chris, for your help. I tried the Web sites. Fantastic!
    Best! Daniel
     
  9. Phil Allison

    Phil Allison Guest

    <


    ** You will have to post that schematic somewhere.

    BTW

    Why are no transistor numbers on it?



    ...... Phil
     
  10. Where will you find the other parts? Loopstick, tuning capacitor, IF
    transformers and audio transformers?

    http://www.rpelectronics.com/Defaul...ail=/English/Content/Divisions/Div_95_650.asp
     
  11. Guest

    Phil:
    The only information on the schematic about these transistors are HF
    andOscillitor, IF,
    Driver, and Audio Output. Thanks! Dan
     
  12. Guest

     
  13. Phil Allison

    Phil Allison Guest

    "Homer J Simpson"

    ** I can see those question coming at us like an express train down a
    tunnel.

    Then he will ask us where to buy a soldering iron.



    ...... Phil
     
  14. Phil Allison

    Phil Allison Guest

    <


    ** So you are refusing to post that schem ?

    Or explain where it came from ?


    ........ Phil
     
  15. Guest

     
  16. Guest

    *****Oh no, Phil. Not at all. But I have no idea how to post it
    online. Am I supposed to
    scan it in first? Or....? I got the schematic from a old dairy kept
    by my uncle. He passed
    away years ago. He was an electrician and a radio hobbist. I guess he
    kep the schematic
    himself for a long time, or perhaps he once wanted to buid it himslef,
    but did. Now my
    kids are interested in building it. Best wishes to you! Dan
     
  17. Phil Allison

    Phil Allison Guest


    ** That would help.

    Then get a real news account instead of the Google abortion you are using.

    Then you can post it on ABSE = " alt.binaries.schematics.electronic"



    Or....? I got the schematic from a old dairy kept

    ** Good thing it was not a plan for a moon rocket......



    ....... Phil
     
  18. You cheapest source would be a $5 radio from Wal-Mart.
     
  19. Chris

    Chris Guest

    Hi, Dan. I like the idea of working from the diary to discover what
    your uncle was thinking. But there are a couple of gotchas here.

    First off, many ideas jotted down in notebooks aren't really
    complete. I know many of mine aren't. He may have been just writing
    in an idea to fill out later.

    Also, an old AM radio design with less than 5 transistors is probably
    taking a shortcut somewhere. Not necessarily a bad thing, but even if
    it's a guaranteed working circuit he just copied down, it's probably
    relying on a trick we'd have to see to evaluate choice of
    transistors. I'd hate to see you and the kids go to the work of
    trying to put something together from scratch and have it fail because
    of some free newsgroup advice. ;-)

    As a bonus, layout in RF circuits is pretty important, to prevent
    unwanted oscillations in the amplifier stages. Working from a
    schematic only, as a relative newbie you might end up going down a
    rabbit trail there, too.

    Old educational transistor radio kits are still being made which are
    guaranteed to work and provide a good educational experience. You
    could do worse than getting the Elenco AM-550TK (5 transistor, no ICs,
    old-style transistor radio kit with good educational brochure
    explaining the circuit), building it with the kids, and then raising a
    glass to the memory of their dad's uncle when they turn it on and it
    works. Similar in many ways, you get all the parts you need, almost
    guaranteed success if you have any soldering and assembly skill, and
    after you're done, you'll understand a lot more about his idea (and
    possibly where the shortcut is).

    http://www.elenco.com/

    Good luck
    Chris
     
  20. But otherwise, it's a question like "where do I get a tunnel diode, I want
    to build this circuit I found in a book or on the internet...". And the
    poster doesn't realize how old the schematic is, or that tunnel diodes
    at their best were mostly a novelty (with some real exceptions) and for
    the hobbyist lasted about a decade (to stretch things a bit).

    In order to stick with the circuit, they will have to work really hard to
    find a tunnel diode, and may pay good money for it. And before that,
    they really should evaluate why they want to make that circuit. IN most
    cases, it's because they don't know better (because they want to build
    something simple, and it certainly is a simple circuit).
    I thought people talked about power germaniums still being made and used.
    The talk would have been in one of the sci.electronics.* newsgroups sometime
    in the past decade, but that's the best I can provide as a pointer.

    Michael
     
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