This circuit is from a 1975 RCA tube manual. It appears elsewhere on the site. R5 depends on the voltage of the amplifier with which it is used and can be changed.
This circuit was found in 1980s Radio Electronics. The circuit includes the power supply. The...
This circuit was found in a former Popular Electronics. The timing is set on the potentiometer and the...
This circuit has appeared on our site several times as a battery status monitor. In this...