Equivalent operational amplifiers can be used on this crystal-controlled oscillator. The circuit is from old documentation and can be changed to operate on other frequencies.
This circuit was found in a 1977s English magazine. The transformer is 15 V x 500 mA but...
In the original circuit a 40431 quadrac is used, but this is not a common component today....
We found this timer circuit in documentation from the 60's. The transistor is a germanium type, and...