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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Optical tachometer (CB9349E)
We found this circuit in a 1970 publication by General Electric. The components can be changed...
Symmetrical 15 V Power Supply (CB19622E)
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Crystal divider by 10 (CB6831E)
Suggested by American documentation from 1968, this circuit divides the frequency of synchronized...