Has anyone any idea about the kinds of circuits in this?

I’ve become a bit interested in how this works, but can’t afford one right now, and can’t find any reference to any of the innards. I did try a wee experiment last week, disconnecting the power from some low voltage tube oscillators I mess about with and using a CV or gate signal to power them instead. While I couldn’t get the heaters in the tubes to light up, when I powered those separately, the gate signals were strong enough to start the oscillation…

Any one any clues on rabbit holes to explore with this kind of thing so I can dig in over the last weeks of winter?