How to make the Pleiades one transistor analog oscillator

This brilliant circuit comes from a game published in Hellas, it existed in the 70s. It had springs for connecting more than one components to a spring. You just tilted one spring with one finger and inserted at the created gap an electronic component. It allowed you to connect resistors, capacitors, 9V battery clip, Morse switch etc to a germanium transistor to create sounds, tones, bird whistles etc. The real thing. It is called Polycyclomatic 1002 or Πολυκυκλωματιστης 1002. The manual allowed easily making 102 circuits. You could improvise by adding your own component values. It is like low level programming using the components themselves. Playing directly with electrons or nature. Perhaps more so that a VCS3 synth. An analog computer. The nature itself.


If you would like to read more on how oscillators work , the Collpits or Hartley or Wein bridge oscillators in Wikipedia is a good place.


This simple oscillator should also be possible to be made with an electron tube operating with only 6V with the trick of connecting a high Megohm resistor from anode to grid to free the electrons. It may be called the Pleiades oscillator. Suitable tubes are EF183 triode connected or ECC82 etc.


How is the simplest possibly audio analog oscillator made:


Ingredients:
A germanium transistor of the OC type, example OC74.
An output transformer with centered tapped hi primary (960mH to 2.1mH)
A 0.1μF ceramic capacitor
A photoresistor
A full range loudspeaker
A 100μF electrolytic capacitor
A 9V battery clip with cable
A 9V batter


A fuse holder with mA fuse


Do not connect the battery until everything is triple checked.


The red (+) cable is connected to the Emitter (E) of the transistor through a fuse.


The black (-) cable is connected to the center tap of the primary of the output transformer.


One end of the primary is connected to base (B) through the .1μF capacitor.


The other end is connected to collector (C).


The photoresistor is connected between B and C.


The speaker is connected to the low impedance secondary of the output transformer.


Ready.


Other variation is a 10KΩ resistor form B to center tap without the photoresistor or substituting the photoresistor there.


A 100μF capacitor can be connected in parallel with the battery holder so that when the battery is disconnected the oscillator keeps playing at continuously varying pitch until the capacitor is discharged.


A push button switch canine added in series with negative of the battery holder cable.


Enjoy!


You may sample it and play it like a synth. With iPad Garageband for example.


If oscillation is not produced, reverse the primary connections.


There is an old saying that goes: if you want to build an amplifier build an oscillator and if you want to build an oscillator build an amplifier.


This circuit is very similar to an single ended class A amplifier. Positive feedback makes the oscillation possible in a similar manner to a PA system producing a loud oscillation when a microphone is brought close to the loudspeaker.