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Radio shack Kit Question on transformer

Discussion in 'Electronic Basics' started by Ken, Dec 30, 2005.

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  1. Ken

    Ken Guest


    I have a kit that I bougfht from RAdio Shack , Here is a link of what I am
    talking about. (

    I would just like to know what are on the transformers in this kit , There
    are no part numbers and I need to replace that part.. The only information I
    have is what is written on the board:
    Output Transformer
    900 8
    ----- -------
    ----- ---------
    Three legs going in and two out with these numbers on top.
    Thank you for your help

    Ken O
  2. Don Bowey

    Don Bowey Guest

    It is an audio output transformer, 900 Ohms to 8 Ohms, to connect to an 8
    Ohm speaker. The 900 Ohm side may be center tapped.

  3. DaveM

    DaveM Guest

    It's just a plain old audio output transformer. You already have the most
    important specs: 900 ohms primary impedance with a center tap, 8 ohms
    secondary impedance. Since this is a learning kit, I'm assuming that it is
    low power, maybe a few hundred milliwatts.
    I suggest one such as this from as a close replacement:

    Catalog # 42TU008
    Primary 800 ohms CT
    Secondary 8 CT
    400 mw
    $ 2.19 each

    It's not an exact match, but, since it's an experimenter's kit, it's
    insignificant. It will still work in the kit.
    Dave M
    MasonDG44 at comcast dot net (Just substitute the appropriate characters in
    the address)

    Never take a laxative and a sleeping pill at the same time!!
  4. Jasen Betts

    Jasen Betts Guest

    looks like a transformer giving 900 ohms centre tapped on one side and 8
    ohms on the other. these were popular in early transistorised products
    (especially those that used 9V batteries)

    if that's one of those "30 in one" "learn electronics" type kits
    any audio transformer that's a "ballpark" match should work.

    For example Jaycar cat# MM-2532 "1000 ohms CT to 8 ohms" (
    I expect there's a supplier nearer you with a similar product.

  5. ian.field1

    ian.field1 Guest

    Maplin do a pair of audio transformers - LT44 & LT77, one is a driver with
    single primary/CT - secondary, the other is for O/P, CT - pri' & single LS
    impedance secondary.
  6. UFO Joe

    UFO Joe Guest

    I've got tons of those kits, going back 30 years.
    I'm an amateur, but if I can help you...

    Radio Shack used to sell them separately.

    (We lost our Radio Shacks here in Canada - the Colonies - they were bought
    out by some oversized American Crap company - Circuit City - now they're
    into going for the big bucks
    with Big Screen TVs and such, anyhow, forgive me, I digress.)

    Radio Shack used to sell them as "Miniature Audio Transformers" if that is
    any help.

    The numbers on the board are the resistance, 900 Ohms in and 8 Ohms out
    (Most speakers are 4-9 Ohms)

    I really hope this helps you to find a suitable replacement.
  7. Ken

    Ken Guest

    Well you are right, Radio shack 200 in 1 kit.
    supplied by a max of 9volts


    And that you for all the help.
  8. Ken

    Ken Guest

    Because I do not have all the working parts. I decided to simulate this
    circuit in pspice. I wanted to add this part the circuit. ( I only worked
    with very simple circuit using a simulator,..capacitor resistor) there are
    many to chosse from also , I wanted to add a transistor A733, there is none
    in the simulator, how do I go about chooosing out of the 100 shown in the
    simulator ??

    thank you

  9. Jim Thompson

    Jim Thompson Guest

    Get/Place Part Q2SA733

    ...Jim Thompson
  10. Robert Baer

    Robert Baer Guest

    Without looking, it is obvious to me; 900 ohm CT input and 8 ohm
    output (to drive speaker or headphone) connects to the output push-pull
    stage of an audio amplifier (or that part of a radio).
  11. Robert Baer

    Robert Baer Guest

    Pick any transistor of the same type (NPN or PNP) and similar use
    (RF, audio or power).
    No need to be picky for popcorn commodity stuff.
  12. safemale

    safemale Guest

    rat shack used to have them
    i think
    ham friend used them in the mic line of his home made rig blaster
    sound card radio interface
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