Interesting valve multivibrator circuit.

[ppppenguin]

I can't see how that circuit works. Where's the time constant? Unless V1 draws grid current C1 is simply a decoupler. Is C2 both coupling the sync pulses and part of the time constant?

The emitter coupled astable (a rather better design than the classic cross coupled astable) is different again.

This may be worth a very quick look. But only a very quick one
https://www.youtube.com/watch?v=Ul4iYmxVsaM