opened up an antique (60s-era) high-voltage power supply at work to fix a loose connector, and that thing had the biggest flyback transformer we've ever seen in it--like the size of a box of tissues

which explains the periodic clicking it makes when in use--it must be operating that thing at extremely low frequency, for it to need such a large transformer. Probably around 2-5 Hz judging by the clicking.

It's from that era when "fully transistorized" was a selling point
-F

and characteristic of that era, there were only maybe three transistors in the thing, along with a bunch of diodes

front panel was two galvanometers for showing the voltage and current, a single-turn potentiometer for setting the current limit, and most interestingly of all, four potentiometers driven by *gears* to rotary displays on the front, with a window to show through the number they're set to

the ones digit could spin freely, while the other three had rollers for ten detents in each
-F