Just a couple of pictures to show the two valve astable multivibrator built as a freeform electronic "art piece" that blinks two (green) LEDs.
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| Two triode astable multivibrator | . |
I used (old, dirty) sockets because I had no idea if the tubes would work, so they allow an easy exchange. And that was needed indeed to balance the blink duty-cycle. I think that at these low voltages these tubes have huge differences in all their parameters.
The tubes are PCF80 or PCF802, filaments are in parallel at 9V, and HT is 9V as well. If you want to give it a try use whatever triodes you have or can get
Since the capacitors are quite small at 1 uF or less, touching one of their legs changes the astable frequency and it feels like a "do not touch" feature.
Next attempt will be to build the blinker with just one triode-pentode valve, that is just one PCF80 or PCF802 in my case with the pentode connected as a triode (g3 with cathode to ground, g2 to anode or +HT).
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| Freeform two triode astable multivibrator (PCF80). |
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