The oscillator circuit switches the electrical current to the primary winding of the transformer on and off in rapid succession. The inductive high voltage created in the secondary windings of the step-up transformer is fed off the secondary coil for the GM tube.
In keeping with Victorian technology I have eliminated the oscillator circuit and replaced it with a manual saw switch. The manual saw switch also switches the electrical current to the primary winding on and off rapidly, but doing so in a mechanical rather than electronic manner.
The heart of the saw switch is the saw itself see figure 1. The saw is approximately 3" in diameter. I cut this saw out of 1/4" thick acrylic plastic, see figure 1.
This saw is cut from 1/4" acrylic plastic. A template for the saw is provided at the end of the article. This saw is attached to a board through the center hole and is allowed to rotate freely. A lever switch is positioned to the saw so that when the saw rotates, the teeth on the saw close and open the contacts on the lever switch. This allows us to rotate the saw, which opens and closes the lever switch. Depending upon how fast we rotate the saw determines the speed of the opening and closing of the lever switch. I call the combination of the saw and lever switch, a saw switch.
Power to our step-up transformer is controlled (turned on and off) by the saw switch.
Figure 1 is a basic saw switch mounted on a flat board. A small machine screw is placed in a small hole drilled on the saw to act as a handle to rotate the saw by hand. Using this flat model makes it easier to understand how this switch functions. When we fit the saw switch into a case, the lever switch will be mounted under the plastic saw to save space.
However this simple set-up is perfect for learning how the saw switch operates and for testing the Geiger Counter circuit before mounting all the components into its enclosure.