This circuit is from an1966 General Electric documentation. The Triac can be equivalent to 6 A or more, mounted on a good heatsink. Any diac can be used.
This oscillator does not carry any resonant circuit, except for the one formed by the crystal...
This is the circuit of a small commercial amplifier from the 1970s from Philips Argentina. The...
This powerful high-fidelity amplifier was described in an article in Radio Electronics magazine in...