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Beginner Questions

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
 
R

Roger Johansson

Jan 1, 1970
0
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!

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.
 
J

julian814

Jan 1, 1970
0
Thanks, Roger. I think I might be able to do that.


Ralph Glatt
 
D

Dave

Jan 1, 1970
0
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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