This harmonic oscillator controlled by crystal was found in an American documentation of the 90's. The circuit uses transistors of the time. Current equivalents can be used.
In the figure we have the typical circuit of a stereo decoder using the TBA450N integrated...
This test for electrolytic capacitors was found in the October 1960 Radio Electronics magazine. Note...
The selected circuit is from the Texas Instruments optoelectronics manual. With it you can receive...