Negative ion detector (CB21001E)

This tube circuit was found in the magazine 73 for radio amateurs in an issue from the 1980s. Note the transformer used to power the circuit.

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RF amplifier (CB20045E)
The transistors are 2N918, 2N3464 and other RF equivalents of the time for Q1. For Q2, 2N3399, 2N2894...
Sensitive triac controller (CB7864E)
This circuit, which can be used as a shield, was found in a 90s Electronic Design. The circuit...
Transistorized Push-Pull Intercom (CB11210E)
This interesting intercom circuit was obtained from an Argentine publication from the 1970s....