Stabilization of the Ten Tec KR20 Keyer

A nagging problem with the Ten Tec model KR20 keyer during four years of use has been an intermittent dit when the keyed character was a dah. Persistent checking showed no component failure. Finally, by monitoring the output of the power supply, a 0.5-volt shift was discovered in the output voltage while keying. This annoying problem vanished and the shift was eliminated when the 270-ohm resistor between the base and ground of Q6 was replaced with a 5.6-volt zener (fig. 2)

Don Peck, W3CRG

Ham Radio page 69 July, 1976