We found this circuit in a 1967 General Electric SCR manual. The time is set to R1 and depends on C1 which must be a low-leak capacitor.
This flasher was found in an old Hands On, but uses common components. The optocoupler can be...
This circuit with output powers of 2 to 3 W depending on the power supply was found in the...
The L3 coil is what basically determines the resonant frequency, around 1 MHz, in this oscillator found...