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Beginner Questions

Discussion in 'Electronic Basics' started by [email protected], Jun 4, 2005.

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  1. Guest

    Hello. I'm getting back into electronics after a long abscense, and I
    need some help. Does anyone know where I might find instructions for
    some of the old Science Fair kits that Radio Shack used to sell? In
    particular, I'm looking for the instructions for the AM transmitter. I
    have a kit, but no instructions. All the parts seem to be there, but
    there's a coil that needs to be wound, and I'm not sure how to go about
    it.

    The only other thing I'd like to know for now is of a good source for
    conductive epoxy. I have an old ZX81 computer with a bad membrane
    keypad, and I'd like to see if I could make another. Seems the keypads
    are hard to come by these days.

    Thanks for any advice!


    Ralph Glatt
     
  2. I have a ZX Spectrum, bought 1984.

    The keyboard gave up a long time ago.

    I built a matrix of wires, the horizontal ones lifted up by small
    pieces of foam plastic, from a table tennis racket, by the way.

    Under it all I placed a picture of the keyboard somehow, so I could
    orient myself.
    Each contact point between a horisontal and vertical wire is a key on
    the keyboard.
    When I touch a wire I push it down one millimeter so it comes into
    contact with the wire under it.

    The rubber pads lift the wire again if I don't push it down too hard,
    so it works quite well. Occasionally I need to move a wire when it gets
    stuck but it is good enough for playing a little with this old museum
    piece.

    The first thing you need is a big picture of the keyboard.
    I have a vague memory that I cut a picture of the keyboard into
    horisontal strips and moved them slightly in relation to each other, so
    the pictures of the keys would fit better into a perpendicular matrix.
    The key rows on the Spectrum are placed diagonally over each other.

    Attach the picture to a base plate, wood or metal, or pcb board
    material.

    Lay out bare copper wires in a matrix, fix them with glue and prop up
    the horisontal wire between each key with some flexible material.
     
  3. julian814

    julian814 Guest

    Thanks, Roger. I think I might be able to do that.


    Ralph Glatt
     
  4. Dave

    Dave Guest

    Hi Ralph,
    Sincus (Timex club in NY is still avtive) and some members have spare
    XZ81's. Email me directly and I will provide a contact for you.
    Dave
     
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