This powerful inverter provides a high-quality sine wave signal. I found it in a Radio Electronics issue from April 1991. The output power is 40W
This is an old test circuit for integrated TTL counters, feeding a Nixie tube, common at the time....
This old oscillator using germanium transistors has a high impedance headphone as inductor to...
This preamp with several inputs using germanium transistors from the time was found in Japanese...