This layout is per the factory schematic found on Univox.org. I swapped the transistor pinouts for modern ones so that 2N5088, 2N5089, MPSA18 and similar can be used. There's added anti-popping pull-down resistor at the input and a polarity protection for your convenience.
Layout is now fixed and verified. Happy building everyone!
Gearmandude's old demo vid: