U170 (says "AOE B A1" mine says "AOE I AH" - I can't find any data on these) has R1304 which also has the same 12v input on the trace going between the two. C173 has 21v on the trace going between those two. I suspect this device generates the higher voltage, but that's a total guess.
That would be a difficult part to desolder and replace, even if you could order them. It might be a case of creating a new circuit to replace it, which is getting vastly more difficult. I'll have to see what devices there are like what I think it is.