Thanks to Dilshan Jayakody for sharing this remarkable throwback project!
HD-1410 is quiet popular iambic keyer which is manufactured around 1970’s by Heathkit. The original HD-1410 keyer is designed using 5 commonly available 74LS series TTL ICs and 8 transistors. Other than iambic operation it has an option to adjust sidetone frequency and support for (external) single-paddle key unit.
In this project we redesign original HD-1410 electronic keyer with today’s commonly available components. In this new design the key components which we replace are transistors, diodes and power supply section of original HD-1410 circuit. Most of the NPN transistors in original design are replaced with KSP42 and KSP10 transistors, and all the PNP transistors are replaced with KSP92 transistors. To keep everything simple we also use same TTL chip-set with this new design.
It’s definitely much simpler-looking than the original version:
Complete build files and more info are here.