Sunday, March 18, 2018

Winding some transformers for the AF amp

I upgraded my coil winding machine. It was like this. It did work but could use a counter.
They have these for $35 - $40 on E-bay so I bought one.
It is really nice to have a counter. I can stop and come back and not lose count. I did have a problem with the shaft. It is about 3/8" so I was limited in the size coil I could wind. I decided to add a chuck and make it universal as the original was.
It was not quite as easy as I hoped but it wasn't to hard. The gear on the drive end is pinned on so it was just a matter of removing the pin and the old shaft would pull out. The other end need threads to screw into the chuck. You can see in the picture the mandrel came with tapered coil holders. They fit in the end of a coil and turn it. So what can be done about that?

The guys in the chemistry lab use these to plug flask. They come in several sizes. I bought a pair in three sizes I thought might be useful and drilled holes in the center for the shaft. I used 1/4" all thread for the mandrel. These worked well with my transformer cores. I used a #8 screw for the mandrel for my pot cores.

With this setup I simply zero the counter and thread the wire. Turn the crank until the counter reaches the desired count. It works well.
I'll have to build that AF amp. When I gather the rest of the parts.

The chief designer for the 40/80 receiver suggested this fab method and I will give it a go on my next project.

This is the circuit as I designed it.

This is the layout I will use to make it. I have the board with the pins already nailed in. I just connect the points with the components and then add jumpers.  You may notice a couple of "twist" when I install the transistor I may switch 5-9 and 7-11 and 15 -19 and 17 -21 to take them out? Just a matter of flipping the transistors/

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