Sony KV-1922 pincushion distortion

[ComboCompact]

I have a late-70s KV-1922 Trinitron with geometry issues... Looks to me like pincushion is at or near its extreme. Not sure of the circumstances of the failure; was like this when I got it.

Hadn't ever run into this on a solid-state consumer set before, but I've encountered it with commercial RGB monitors and it's never an easy fix. My hunch is that adjusting the pin amp pot won't have any effect, though to be fair I haven't cracked it open yet.

Before I attempt to mess with pin amp/phase (and potentially start tearing my hair out) has anybody fixed this on a similar set before? Any general hints, or a quick checklist of things to look at?