rasz_pl wrote on 2022-01-31, 11:57:

Searching for UM82C480 will give you limited datasheet. At least it offers internal block diagram and pinout

Nice, thanks. It looks like the trace going to pin 19 of U52 goes to 141 of the 82C481, which is a ground. So the R32 is always connected and can't be turned on or off, so I was wrong about that.