Morse Keyer Redesign and Rebuild


Posted on Feb 6, 2014

Two cheap CMOS ICs and a few transistors was all that was required to rebuild my elderly TTL automatic morse keyer into a low current lightweight battery powered iambic morse keyer. Sometime over the past year or two, my elderly Accu-Keyer gave up the ghost and died. I built it more than 30 years ago (!) from the original TTL IC-based design


Morse Keyer Redesign and Rebuild
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published in the ARRL Handbook. It was an accurate copy of the original, right down to the printed circuit board which I made using nail polish as resist and ferric chloride etchant. As I was tearing the old keyer apart, I instantly recognised the PCB production method I`d used by the quality of the resulting PCB. It was not very pretty, and I certainly could not reuse the PCB simply by replacing the dead ICs with new CMOS devices. In those days, the Accu-Keyer was the most popular design. Most of those keyers used TTL chips, and the current drain worked out to be a few hundred milliamps. Running it off batteries was hardly practical, and I never tried. But there were times when it would have been useful. In fact, I was never very happy with the keyer. The power supply was my biggest gripe, and my own fault. I made it using a rewound transformer. I was a poor high school student in those days, without much money to spend on the hobby. To get the right voltage for the power supply - I needed 5VDC - I found a transformer somewhere, pulled it apart, and rewound the secondary by hand. The problem was that the darned transformer used to hum like crazy because I was unable to clamp up the laminations adequately. I guess I could have dipped it in varnish or something, but I never got around to it. The hum wasn`t too bad when it was all enclosed inside the little box. Even so, every time I turned it on, I would hear that hum, and...




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