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
Click here to download the full size of the above Circuit.

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...

Leave Comment

characters left:

New Circuits



Popular Circuits

Mains Voltage Checker
Delayed headlights circuit
Radiation Sensor Circuit
Schematics Serial Temperature Sensor Data Logger
Hearing Aids Circuit
Micore Reader IC Family Directly Matched Antenna Design