The core of the push-pull excitation is a pair of switching transistors and a pair of resistors. The voltage supply, trafo, cascade and control (train of pulses) are all separate parts. In order to be able to quickly change transistors, push-pull core is assembled on a protoboard. The whole high-voltage generator is then assembled from parts (see the photos).
The schematic is available in Fig. 17 in the following document
https://o-esd.etf.bg.ac.rs/forgejo/dragan.olcan/O-ESD/raw/branch/main/Documents/O-ESD-02.pdf
