[greenbit]

Found a schematic for the 4016/4032 at https://www.zimmers.net/anonftp/pub/cbm/schematics/computers...

The vertical deflection drive appears to have some feedback, so maybe that could constitute an oscillator, but I can't see any feedback at all in the horizontal section, it looks entirely feed-forward. I get the impression they were just integrating the square wave into a ramp. The diagram shows 15us low out of only 50us total line time, which seems like quite unlike the typical 15.75 kHz sync of the time. I recall getting hold of the 6845 datasheet and trying in earnest to understand how to program that chip, and was baffled that the reference set of register values wouldn't produce a display. The fact I was missing at the time was that one had to start from 20kHz for the horizontal refresh.